RecyclerView.LayoutManager


public abstract class RecyclerView.LayoutManager

Known direct subclasses
GridLayoutManager

A RecyclerView.LayoutManager implementation that lays out items in a grid for leanback VerticalGridView and HorizontalGridView.

LinearLayoutManager

A RecyclerView.LayoutManager implementation which provides similar functionality to android.widget.ListView.

StaggeredGridLayoutManager

A LayoutManager that lays out children in a staggered grid formation.

Known indirect subclasses
GridLayoutManager

A RecyclerView.LayoutManager implementations that lays out items in a grid.

WearableLinearLayoutManager

This wear-specific implementation of LinearLayoutManager provides basic offsetting logic for updating child layout.


A LayoutManager is responsible for measuring and positioning item views within a RecyclerView as well as determining the policy for when to recycle item views that are no longer visible to the user. By changing the LayoutManager a RecyclerView can be used to implement a standard vertically scrolling list, a uniform grid, staggered grids, horizontally scrolling collections and more. Several stock layout managers are provided for general use.

If the LayoutManager specifies a default constructor or one with the signature (Context, AttributeSet, int, int), RecyclerView will instantiate and set the LayoutManager when being inflated. Most used properties can be then obtained from getProperties. In case a LayoutManager specifies both constructors, the non-default constructor will take precedence.

Summary

Nested types

Interface for LayoutManagers to request items to be prefetched, based on position, with specified distance from viewport, which indicates priority.

Some general properties that a LayoutManager may want to use.

Public constructors

Public methods

void

To be called only during onLayoutChildren to add a view to the layout that is known to be going away, either because it has been removed or because it is actually not in the visible portion of the container but is being laid out in order to inform RecyclerView in how to animate the item out of view.

void
addDisappearingView(View child, int index)

To be called only during onLayoutChildren to add a view to the layout that is known to be going away, either because it has been removed or because it is actually not in the visible portion of the container but is being laid out in order to inform RecyclerView in how to animate the item out of view.

void
addView(View child)

Add a view to the currently attached RecyclerView if needed.

void
addView(View child, int index)

Add a view to the currently attached RecyclerView if needed.

void

Checks if RecyclerView is in the middle of a layout or scroll and throws an IllegalStateException if it is not.

void

Checks if RecyclerView is in the middle of a layout or scroll and throws an IllegalStateException if it is.

void

Reattach a previously detached view.

void
attachView(@NonNull View child, int index)

Reattach a previously detached view.

void
attachView(@NonNull View child, int index, RecyclerView.LayoutParams lp)

Reattach a previously detached view.

void
calculateItemDecorationsForChild(
    @NonNull View child,
    @NonNull Rect outRect
)

Calculates the item decor insets applied to the given child and updates the provided Rect instance with the inset values.

boolean

Query if horizontal scrolling is currently supported.

boolean

Query if vertical scrolling is currently supported.

boolean

Determines the validity of the supplied LayoutParams object.

static int
chooseSize(int spec, int desired, int min)

Chooses a size from the given specs and parameters that is closest to the desired size and also complies with the spec.

void
collectAdjacentPrefetchPositions(
    int dx,
    int dy,
    RecyclerView.State state,
    RecyclerView.LayoutManager.LayoutPrefetchRegistry layoutPrefetchRegistry
)

Gather all positions from the LayoutManager to be prefetched, given specified momentum.

void
collectInitialPrefetchPositions(
    int adapterItemCount,
    RecyclerView.LayoutManager.LayoutPrefetchRegistry layoutPrefetchRegistry
)

Gather all positions from the LayoutManager to be prefetched in preperation for its RecyclerView to come on screen, due to the movement of another, containing RecyclerView.

int

Override this method if you want to support scroll bars.

int

Override this method if you want to support scroll bars.

int

Override this method if you want to support scroll bars.

int

Override this method if you want to support scroll bars.

int

Override this method if you want to support scroll bars.

int

Override this method if you want to support scroll bars.

void

Temporarily detach and scrap all currently attached child views.

void
detachAndScrapView(
    @NonNull View child,
    @NonNull RecyclerView.Recycler recycler
)

Detach a child view and add it to a Recycler's scrap heap.

void

Detach a child view and add it to a Recycler's scrap heap.

void

Temporarily detach a child view.

void
detachViewAt(int index)

Temporarily detach a child view.

void

Ends all animations on the view created by the ItemAnimator.

@Nullable View

Traverses the ancestors of the given view and returns the item view that contains it and also a direct child of the LayoutManager.

@Nullable View
findViewByPosition(int position)

Finds the view which represents the given adapter position.

abstract RecyclerView.LayoutParams

Create a default LayoutParams object for a child of the RecyclerView.

RecyclerView.LayoutParams

Create a LayoutParams object suitable for this LayoutManager, copying relevant values from the supplied LayoutParams object if possible.

RecyclerView.LayoutParams

Create a LayoutParams object suitable for this LayoutManager from an inflated layout resource.

int

Returns offset of the RecyclerView's text baseline from the its top boundary.

int

Returns the total height of item decorations applied to child's bottom.

@Nullable View
getChildAt(int index)

Return the child view at the given index

int

Return the current number of child views attached to the parent RecyclerView.

static int
getChildMeasureSpec(
    int parentSize,
    int padding,
    int childDimension,
    boolean canScroll
)

This method is deprecated.

use getChildMeasureSpec

static int
getChildMeasureSpec(
    int parentSize,
    int parentMode,
    int padding,
    int childDimension,
    boolean canScroll
)

Calculate a MeasureSpec value for measuring a child view in one dimension.

boolean

Check if the RecyclerView is configured to clip child views to its padding.

int

Returns the number of columns for accessibility.

int

Returns the bottom edge of the given child view within its parent, offset by any applied ItemDecorations.

void

Returns the bounds of the view including its decoration and margins.

int

Returns the left edge of the given child view within its parent, offset by any applied ItemDecorations.

int

Returns the measured height of the given child, plus the additional size of any insets applied by ItemDecorations.

int

Returns the measured width of the given child, plus the additional size of any insets applied by ItemDecorations.

int

Returns the right edge of the given child view within its parent, offset by any applied ItemDecorations.

int

Returns the top edge of the given child view within its parent, offset by any applied ItemDecorations.

@Nullable View

Returns the item View which has or contains focus.

@Px int

Returns the height that is currently relevant to the LayoutManager.

int

Return the height measurement spec mode that is currently relevant to the LayoutManager.

int

Returns the number of items in the adapter bound to the parent RecyclerView.

int

Returns the View type defined by the adapter.

int

Returns the resolved layout direction for this RecyclerView.

int

Returns the total width of item decorations applied to child's left.

@Px int
@Px int
@Px int

Return the bottom padding of the parent RecyclerView

@Px int

Return the end padding of the parent RecyclerView

@Px int

Return the left padding of the parent RecyclerView

@Px int

Return the right padding of the parent RecyclerView

@Px int

Return the start padding of the parent RecyclerView

@Px int

Return the top padding of the parent RecyclerView

int

Returns the adapter position of the item represented by the given View.

static RecyclerView.LayoutManager.Properties
getProperties(
    @NonNull Context context,
    @Nullable AttributeSet attrs,
    int defStyleAttr,
    int defStyleRes
)

Parse the xml attributes to get the most common properties used by layout managers.

int

Returns the total width of item decorations applied to child's right.

int

Returns the number of rows for accessibility.

int

Returns the selection mode for accessibility.

int

Returns the total height of item decorations applied to child's top.

void
getTransformedBoundingBox(
    @NonNull View child,
    boolean includeDecorInsets,
    @NonNull Rect out
)

Calculates the bounding box of the View while taking into account its matrix changes (translation, scale etc) with respect to the RecyclerView.

@Px int

Returns the width that is currently relevant to the LayoutManager.

int

Return the width measurement spec mode that is currently relevant to the LayoutManager.

boolean

Returns true if the RecyclerView this LayoutManager is bound to has or contains focus.

void

Flags a view so that it will not be scrapped or recycled.

boolean

Returns whether LayoutManager is currently attached to a RecyclerView which is attached to a window.

boolean

Returns whether the measuring pass of layout should use the AutoMeasure mechanism of RecyclerView or if it should be done by the LayoutManager's implementation of onMeasure.

boolean

Returns true if the RecyclerView this LayoutManager is bound to has focus.

final boolean

Sets whether the LayoutManager should be queried for views outside of its viewport while the UI thread is idle between frames.

boolean

Returns whether layout is hierarchical or not to be used for accessibility.

boolean

Query if the layout is in reverse order.

boolean

In addition to the View Framework's measurement cache, RecyclerView uses its own additional measurement cache for its children to avoid re-measuring them when not necessary.

boolean
boolean
isViewPartiallyVisible(
    @NonNull View child,
    boolean completelyVisible,
    boolean acceptEndPointInclusion
)

Returns whether the given child view is partially or fully visible within the padded bounded area of RecyclerView, depending on the input parameters.

void
layoutDecorated(
    @NonNull View child,
    int left,
    int top,
    int right,
    int bottom
)

Lay out the given child view within the RecyclerView using coordinates that include any current ItemDecorations.

void
layoutDecoratedWithMargins(
    @NonNull View child,
    int left,
    int top,
    int right,
    int bottom
)

Lay out the given child view within the RecyclerView using coordinates that include any current ItemDecorations and margins.

void
measureChild(@NonNull View child, int widthUsed, int heightUsed)

Measure a child view using standard measurement policy, taking the padding of the parent RecyclerView and any added item decorations into account.

void
measureChildWithMargins(
    @NonNull View child,
    int widthUsed,
    int heightUsed
)

Measure a child view using standard measurement policy, taking the padding of the parent RecyclerView, any added item decorations and the child margins into account.

void
moveView(int fromIndex, int toIndex)

Moves a View from one position to another.

void

Offset all child views attached to the parent RecyclerView by dx pixels along the horizontal axis.

void

Offset all child views attached to the parent RecyclerView by dy pixels along the vertical axis.

void

Called if the RecyclerView this LayoutManager is bound to has a different adapter set via setAdapter or swapAdapter.

boolean
onAddFocusables(
    @NonNull RecyclerView recyclerView,
    @NonNull ArrayList<View> views,
    int direction,
    int focusableMode
)

Called to populate focusable views within the RecyclerView.

void

Called when this LayoutManager is both attached to a RecyclerView and that RecyclerView is attached to a window.

void

This method is deprecated.

override onDetachedFromWindow

void

Called when this LayoutManager is detached from its parent RecyclerView or when its parent RecyclerView is detached from its window.

@Nullable View
onFocusSearchFailed(
    @NonNull View focused,
    int direction,
    @NonNull RecyclerView.Recycler recycler,
    @NonNull RecyclerView.State state
)

Called when searching for a focusable view in the given direction has failed for the current content of the RecyclerView.

void
void

Called by the accessibility delegate to initialize an accessibility event.

void

Called by the AccessibilityDelegate when the information about the current layout should be populated.

void

Called by the AccessibilityDelegate when the accessibility information for a specific item should be populated.

@Nullable View
onInterceptFocusSearch(@NonNull View focused, int direction)

This method gives a LayoutManager an opportunity to intercept the initial focus search before the default behavior of FocusFinder is used.

void
onItemsAdded(
    @NonNull RecyclerView recyclerView,
    int positionStart,
    int itemCount
)

Called when items have been added to the adapter.

void

Called in response to a call to notifyDataSetChanged or swapAdapter ()} and signals that the the entire data set has changed.

void
onItemsMoved(
    @NonNull RecyclerView recyclerView,
    int from,
    int to,
    int itemCount
)

Called when an item is moved withing the adapter.

void
onItemsRemoved(
    @NonNull RecyclerView recyclerView,
    int positionStart,
    int itemCount
)

Called when items have been removed from the adapter.

void
onItemsUpdated(
    @NonNull RecyclerView recyclerView,
    int positionStart,
    int itemCount
)

Called when items have been changed in the adapter.

void
onItemsUpdated(
    @NonNull RecyclerView recyclerView,
    int positionStart,
    int itemCount,
    @Nullable Object payload
)

Called when items have been changed in the adapter and with optional payload.

void

Lay out all relevant child views from the given adapter.

void

Called after a full layout calculation is finished.

void
onMeasure(
    @NonNull RecyclerView.Recycler recycler,
    @NonNull RecyclerView.State state,
    int widthSpec,
    int heightSpec
)

Measure the attached RecyclerView.

boolean
onRequestChildFocus(
    @NonNull RecyclerView parent,
    @NonNull View child,
    @Nullable View focused
)

This method is deprecated.

Use onRequestChildFocus

boolean
onRequestChildFocus(
    @NonNull RecyclerView parent,
    @NonNull RecyclerView.State state,
    @NonNull View child,
    @Nullable View focused
)

Called when a descendant view of the RecyclerView requests focus.

void

Called when the RecyclerView is ready to restore the state based on a previous RecyclerView.

@Nullable Parcelable

Called when the LayoutManager should save its state.

void

RecyclerView calls this method to notify LayoutManager that scroll state has changed.

boolean
performAccessibilityAction(
    @NonNull RecyclerView.Recycler recycler,
    @NonNull RecyclerView.State state,
    int action,
    @Nullable Bundle args
)

Called by AccessibilityDelegate when an action is requested from the RecyclerView.

boolean
performAccessibilityActionForItem(
    @NonNull RecyclerView.Recycler recycler,
    @NonNull RecyclerView.State state,
    @NonNull View view,
    int action,
    @Nullable Bundle args
)

Called by AccessibilityDelegate when an accessibility action is requested on one of the children of LayoutManager.

void

Causes the Runnable to execute on the next animation time step.

void

Remove all views from the currently attached RecyclerView.

void

Removes all views and recycles them using the given recycler.

void
removeAndRecycleView(
    @NonNull View child,
    @NonNull RecyclerView.Recycler recycler
)

Remove a child view and recycle it using the given Recycler.

void
removeAndRecycleViewAt(
    int index,
    @NonNull RecyclerView.Recycler recycler
)

Remove a child view and recycle it using the given Recycler.

boolean

Removes the specified Runnable from the message queue.

void

Finish removing a view that was previously temporarily detached.

void

Remove a view from the currently attached RecyclerView if needed.

void
removeViewAt(int index)

Remove a view from the currently attached RecyclerView if needed.

boolean
requestChildRectangleOnScreen(
    @NonNull RecyclerView parent,
    @NonNull View child,
    @NonNull Rect rect,
    boolean immediate
)

Called when a child of the RecyclerView wants a particular rectangle to be positioned onto the screen.

boolean
requestChildRectangleOnScreen(
    @NonNull RecyclerView parent,
    @NonNull View child,
    @NonNull Rect rect,
    boolean immediate,
    boolean focusedChildVisible
)

Requests that the given child of the RecyclerView be positioned onto the screen.

void

Calls RecyclerView#requestLayout on the underlying RecyclerView

void

A LayoutManager can call this method to force RecyclerView to run simple animations in the next layout pass, even if there is not any trigger to do so.

int
scrollHorizontallyBy(
    int dx,
    RecyclerView.Recycler recycler,
    RecyclerView.State state
)

Scroll horizontally by dx pixels in screen coordinates and return the distance traveled.

void
scrollToPosition(int position)

Scroll to the specified adapter position.

int
scrollVerticallyBy(
    int dy,
    RecyclerView.Recycler recycler,
    RecyclerView.State state
)

Scroll vertically by dy pixels in screen coordinates and return the distance traveled.

void
setAutoMeasureEnabled(boolean enabled)

This method is deprecated.

Implementors of LayoutManager should define whether or not it uses AutoMeasure by overriding isAutoMeasureEnabled.

final void
setItemPrefetchEnabled(boolean enabled)

Sets whether the LayoutManager should be queried for views outside of its viewport while the UI thread is idle between frames.

void
setMeasuredDimension(int widthSize, int heightSize)

Set the measured dimensions of the host RecyclerView.

void
setMeasuredDimension(Rect childrenBounds, int wSpec, int hSpec)

Sets the measured dimensions from the given bounding box of the children and the measurement specs that were passed into onMeasure.

void
setMeasurementCacheEnabled(boolean measurementCacheEnabled)

Sets whether RecyclerView should use its own measurement cache for the children.

void
smoothScrollToPosition(
    RecyclerView recyclerView,
    RecyclerView.State state,
    int position
)

Smooth scroll to the specified adapter position.

void

Starts a smooth scroll using the provided SmoothScroller.

void

View can be scrapped and recycled again.

boolean

Returns whether this LayoutManager supports "predictive item animations".

Public constructors

LayoutManager

Added in 1.0.0
public LayoutManager()

Public methods

addDisappearingView

Added in 1.0.0
public void addDisappearingView(View child)

To be called only during onLayoutChildren to add a view to the layout that is known to be going away, either because it has been removed or because it is actually not in the visible portion of the container but is being laid out in order to inform RecyclerView in how to animate the item out of view.

Views added via this method are going to be invisible to LayoutManager after the dispatchLayout pass is complete. They cannot be retrieved via getChildAt or won't be included in getChildCount method.

Parameters
View child

View to add and then remove with animation.

addDisappearingView

Added in 1.0.0
public void addDisappearingView(View child, int index)

To be called only during onLayoutChildren to add a view to the layout that is known to be going away, either because it has been removed or because it is actually not in the visible portion of the container but is being laid out in order to inform RecyclerView in how to animate the item out of view.

Views added via this method are going to be invisible to LayoutManager after the dispatchLayout pass is complete. They cannot be retrieved via getChildAt or won't be included in getChildCount method.

Parameters
View child

View to add and then remove with animation.

int index

Index of the view.

addView

Added in 1.0.0
public void addView(View child)

Add a view to the currently attached RecyclerView if needed. LayoutManagers should use this method to add views obtained from a Recycler using getViewForPosition.

Parameters
View child

View to add

addView

Added in 1.0.0
public void addView(View child, int index)

Add a view to the currently attached RecyclerView if needed. LayoutManagers should use this method to add views obtained from a Recycler using getViewForPosition.

Parameters
View child

View to add

int index

Index to add child at

assertInLayoutOrScroll

Added in 1.0.0
public void assertInLayoutOrScroll(String message)

Checks if RecyclerView is in the middle of a layout or scroll and throws an IllegalStateException if it is not.

Parameters
String message

The message for the exception. Can be null.

assertNotInLayoutOrScroll

Added in 1.0.0
public void assertNotInLayoutOrScroll(String message)

Checks if RecyclerView is in the middle of a layout or scroll and throws an IllegalStateException if it is.

Parameters
String message

The message for the exception. Can be null.

attachView

Added in 1.0.0
public void attachView(@NonNull View child)

Reattach a previously detached view. This method should not be used to reattach views that were previously detachAndScrapView scrapped}.

Parameters
@NonNull View child

Child to reattach

attachView

Added in 1.0.0
public void attachView(@NonNull View child, int index)

Reattach a previously detached view. This method should not be used to reattach views that were previously detachAndScrapView scrapped}.

Parameters
@NonNull View child

Child to reattach

int index

Intended child index for child

attachView

Added in 1.0.0
public void attachView(@NonNull View child, int index, RecyclerView.LayoutParams lp)

Reattach a previously detached view. This method should not be used to reattach views that were previously detachAndScrapView scrapped}.

Parameters
@NonNull View child

Child to reattach

int index

Intended child index for child

RecyclerView.LayoutParams lp

LayoutParams for child

calculateItemDecorationsForChild

Added in 1.0.0
public void calculateItemDecorationsForChild(
    @NonNull View child,
    @NonNull Rect outRect
)

Calculates the item decor insets applied to the given child and updates the provided Rect instance with the inset values.

  • The Rect's left is set to the total width of left decorations.
  • The Rect's top is set to the total height of top decorations.
  • The Rect's right is set to the total width of right decorations.
  • The Rect's bottom is set to total height of bottom decorations.

Note that item decorations are automatically calculated when one of the LayoutManager's measure child methods is called. If you need to measure the child with custom specs via measure, you can use this method to get decorations.

Parameters
@NonNull View child

The child view whose decorations should be calculated

@NonNull Rect outRect

The Rect to hold result values

canScrollHorizontally

Added in 1.0.0
public boolean canScrollHorizontally()

Query if horizontal scrolling is currently supported. The default implementation returns false.

Returns
boolean

True if this LayoutManager can scroll the current contents horizontally

canScrollVertically

Added in 1.0.0
public boolean canScrollVertically()

Query if vertical scrolling is currently supported. The default implementation returns false.

Returns
boolean

True if this LayoutManager can scroll the current contents vertically

checkLayoutParams

Added in 1.0.0
public boolean checkLayoutParams(RecyclerView.LayoutParams lp)

Determines the validity of the supplied LayoutParams object.

This should check to make sure that the object is of the correct type and all values are within acceptable ranges. The default implementation returns true for non-null params.

Parameters
RecyclerView.LayoutParams lp

LayoutParams object to check

Returns
boolean

true if this LayoutParams object is valid, false otherwise

chooseSize

Added in 1.0.0
public static int chooseSize(int spec, int desired, int min)

Chooses a size from the given specs and parameters that is closest to the desired size and also complies with the spec.

Parameters
int spec

The measureSpec

int desired

The preferred measurement

int min

The minimum value

Returns
int

A size that fits to the given specs

collectAdjacentPrefetchPositions

Added in 1.0.0
public void collectAdjacentPrefetchPositions(
    int dx,
    int dy,
    RecyclerView.State state,
    RecyclerView.LayoutManager.LayoutPrefetchRegistry layoutPrefetchRegistry
)

Gather all positions from the LayoutManager to be prefetched, given specified momentum.

If item prefetch is enabled, this method is called in between traversals to gather which positions the LayoutManager will soon need, given upcoming movement in subsequent traversals.

The LayoutManager should call addPosition for each item to be prepared, and these positions will have their ViewHolders created and bound, if there is sufficient time available, in advance of being needed by a scroll or layout.

Parameters
int dx

X movement component.

int dy

Y movement component.

RecyclerView.State state

State of RecyclerView

RecyclerView.LayoutManager.LayoutPrefetchRegistry layoutPrefetchRegistry

PrefetchRegistry to add prefetch entries into.

collectInitialPrefetchPositions

Added in 1.0.0
public void collectInitialPrefetchPositions(
    int adapterItemCount,
    RecyclerView.LayoutManager.LayoutPrefetchRegistry layoutPrefetchRegistry
)

Gather all positions from the LayoutManager to be prefetched in preperation for its RecyclerView to come on screen, due to the movement of another, containing RecyclerView.

This method is only called when a RecyclerView is nested in another RecyclerView.

If item prefetch is enabled for this LayoutManager, as well in another containing LayoutManager, this method is called in between draw traversals to gather which positions this LayoutManager will first need, once it appears on the screen.

For example, if this LayoutManager represents a horizontally scrolling list within a vertically scrolling LayoutManager, this method would be called when the horizontal list is about to come onscreen.

The LayoutManager should call addPosition for each item to be prepared, and these positions will have their ViewHolders created and bound, if there is sufficient time available, in advance of being needed by a scroll or layout.

Parameters
int adapterItemCount

number of items in the associated adapter.

RecyclerView.LayoutManager.LayoutPrefetchRegistry layoutPrefetchRegistry

PrefetchRegistry to add prefetch entries into.

computeHorizontalScrollExtent

Added in 1.0.0
public int computeHorizontalScrollExtent(@NonNull RecyclerView.State state)

Override this method if you want to support scroll bars.

Read computeHorizontalScrollExtent for details.

Default implementation returns 0.

Parameters
@NonNull RecyclerView.State state

Current state of RecyclerView

Returns
int

The horizontal extent of the scrollbar's thumb

computeHorizontalScrollOffset

Added in 1.0.0
public int computeHorizontalScrollOffset(@NonNull RecyclerView.State state)

Override this method if you want to support scroll bars.

Read computeHorizontalScrollOffset for details.

Default implementation returns 0.

Parameters
@NonNull RecyclerView.State state

Current State of RecyclerView where you can find total item count

Returns
int

The horizontal offset of the scrollbar's thumb

computeHorizontalScrollRange

Added in 1.0.0
public int computeHorizontalScrollRange(@NonNull RecyclerView.State state)

Override this method if you want to support scroll bars.

Read computeHorizontalScrollRange for details.

Default implementation returns 0.

Parameters
@NonNull RecyclerView.State state

Current State of RecyclerView where you can find total item count

Returns
int

The total horizontal range represented by the horizontal scrollbar

computeVerticalScrollExtent

Added in 1.0.0
public int computeVerticalScrollExtent(@NonNull RecyclerView.State state)

Override this method if you want to support scroll bars.

Read computeVerticalScrollExtent for details.

Default implementation returns 0.

Parameters
@NonNull RecyclerView.State state

Current state of RecyclerView

Returns
int

The vertical extent of the scrollbar's thumb

computeVerticalScrollOffset

Added in 1.0.0
public int computeVerticalScrollOffset(@NonNull RecyclerView.State state)

Override this method if you want to support scroll bars.

Read computeVerticalScrollOffset for details.

Default implementation returns 0.

Parameters
@NonNull RecyclerView.State state

Current State of RecyclerView where you can find total item count

Returns
int

The vertical offset of the scrollbar's thumb

computeVerticalScrollRange

Added in 1.0.0
public int computeVerticalScrollRange(@NonNull RecyclerView.State state)

Override this method if you want to support scroll bars.

Read computeVerticalScrollRange for details.

Default implementation returns 0.

Parameters
@NonNull RecyclerView.State state

Current State of RecyclerView where you can find total item count

Returns
int

The total vertical range represented by the vertical scrollbar

detachAndScrapAttachedViews

Added in 1.0.0
public void detachAndScrapAttachedViews(@NonNull RecyclerView.Recycler recycler)

Temporarily detach and scrap all currently attached child views. Views will be scrapped into the given Recycler. The Recycler may prefer to reuse scrap views before other views that were previously recycled.

Parameters
@NonNull RecyclerView.Recycler recycler

Recycler to scrap views into

detachAndScrapView

Added in 1.0.0
public void detachAndScrapView(
    @NonNull View child,
    @NonNull RecyclerView.Recycler recycler
)

Detach a child view and add it to a Recycler's scrap heap.

Scrapping a view allows it to be rebound and reused to show updated or different data.

Parameters
@NonNull View child

Child to detach and scrap

@NonNull RecyclerView.Recycler recycler

Recycler to deposit the new scrap view into

detachAndScrapViewAt

Added in 1.0.0
public void detachAndScrapViewAt(int index, @NonNull RecyclerView.Recycler recycler)

Detach a child view and add it to a Recycler's scrap heap.

Scrapping a view allows it to be rebound and reused to show updated or different data.

Parameters
int index

Index of child to detach and scrap

@NonNull RecyclerView.Recycler recycler

Recycler to deposit the new scrap view into

detachView

Added in 1.0.0
public void detachView(@NonNull View child)

Temporarily detach a child view.

LayoutManagers may want to perform a lightweight detach operation to rearrange views currently attached to the RecyclerView. Generally LayoutManager implementations will want to use detachAndScrapView so that the detached view may be rebound and reused.

If a LayoutManager uses this method to detach a view, it mustreattach or fully remove the detached view before the LayoutManager entry point method called by RecyclerView returns.

Parameters
@NonNull View child

Child to detach

detachViewAt

Added in 1.0.0
public void detachViewAt(int index)

Temporarily detach a child view.

LayoutManagers may want to perform a lightweight detach operation to rearrange views currently attached to the RecyclerView. Generally LayoutManager implementations will want to use detachAndScrapView so that the detached view may be rebound and reused.

If a LayoutManager uses this method to detach a view, it mustreattach or fully remove the detached view before the LayoutManager entry point method called by RecyclerView returns.

Parameters
int index

Index of the child to detach

endAnimation

Added in 1.0.0
public void endAnimation(View view)

Ends all animations on the view created by the ItemAnimator.

Parameters
View view

The View for which the animations should be ended.

See also
endAnimations

findContainingItemView

Added in 1.0.0
public @Nullable View findContainingItemView(@NonNull View view)

Traverses the ancestors of the given view and returns the item view that contains it and also a direct child of the LayoutManager.

Note that this method may return null if the view is a child of the RecyclerView but not a child of the LayoutManager (e.g. running a disappear animation).

Parameters
@NonNull View view

The view that is a descendant of the LayoutManager.

Returns
@Nullable View

The direct child of the LayoutManager which contains the given view or null if the provided view is not a descendant of this LayoutManager.

findViewByPosition

Added in 1.0.0
public @Nullable View findViewByPosition(int position)

Finds the view which represents the given adapter position.

This method traverses each child since it has no information about child order. Override this method to improve performance if your LayoutManager keeps data about child views.

If a view is ignored via ignoreView, it is also ignored by this method.

Parameters
int position

Position of the item in adapter

Returns
@Nullable View

The child view that represents the given position or null if the position is not laid out

generateDefaultLayoutParams

Added in 1.0.0
public abstract RecyclerView.LayoutParams generateDefaultLayoutParams()

Create a default LayoutParams object for a child of the RecyclerView.

LayoutManagers will often want to use a custom LayoutParams type to store extra information specific to the layout. Client code should subclass RecyclerView.LayoutParams for this purpose.

Important: if you use your own custom LayoutParams type you must also override checkLayoutParams, generateLayoutParams and generateLayoutParams.

Returns
RecyclerView.LayoutParams

A new LayoutParams for a child view

generateLayoutParams

Added in 1.0.0
public RecyclerView.LayoutParams generateLayoutParams(ViewGroup.LayoutParams lp)

Create a LayoutParams object suitable for this LayoutManager, copying relevant values from the supplied LayoutParams object if possible.

Important: if you use your own custom LayoutParams type you must also override checkLayoutParams, generateLayoutParams and generateLayoutParams.

Parameters
ViewGroup.LayoutParams lp

Source LayoutParams object to copy values from

Returns
RecyclerView.LayoutParams

a new LayoutParams object

generateLayoutParams

Added in 1.0.0
public RecyclerView.LayoutParams generateLayoutParams(Context c, AttributeSet attrs)

Create a LayoutParams object suitable for this LayoutManager from an inflated layout resource.

Important: if you use your own custom LayoutParams type you must also override checkLayoutParams, generateLayoutParams and generateLayoutParams.

Parameters
Context c

Context for obtaining styled attributes

AttributeSet attrs

AttributeSet describing the supplied arguments

Returns
RecyclerView.LayoutParams

a new LayoutParams object

getBaseline

Added in 1.0.0
public int getBaseline()

Returns offset of the RecyclerView's text baseline from the its top boundary.

Returns
int

The offset of the RecyclerView's text baseline from the its top boundary; -1 if there is no baseline.

getBottomDecorationHeight

Added in 1.0.0
public int getBottomDecorationHeight(@NonNull View child)

Returns the total height of item decorations applied to child's bottom.

Note that this value is not updated until the View is measured or calculateItemDecorationsForChild is called.

Parameters
@NonNull View child

Child to query

Returns
int

The total height of item decorations applied to the child's bottom.

getChildAt

Added in 1.0.0
public @Nullable View getChildAt(int index)

Return the child view at the given index

Parameters
int index

Index of child to return

Returns
@Nullable View

Child view at index

getChildCount

Added in 1.0.0
public int getChildCount()

Return the current number of child views attached to the parent RecyclerView. This does not include child views that were temporarily detached and/or scrapped.

Returns
int

Number of attached children

getChildMeasureSpec

Added in 1.0.0
Deprecated in 1.0.0
public static int getChildMeasureSpec(
    int parentSize,
    int padding,
    int childDimension,
    boolean canScroll
)

Calculate a MeasureSpec value for measuring a child view in one dimension.

Parameters
int parentSize

Size of the parent view where the child will be placed

int padding

Total space currently consumed by other elements of the parent

int childDimension

Desired size of the child view, or MATCH_PARENT/WRAP_CONTENT. Generally obtained from the child view's LayoutParams

boolean canScroll

true if the parent RecyclerView can scroll in this dimension

Returns
int

a MeasureSpec value for the child view

getChildMeasureSpec

Added in 1.0.0
public static int getChildMeasureSpec(
    int parentSize,
    int parentMode,
    int padding,
    int childDimension,
    boolean canScroll
)

Calculate a MeasureSpec value for measuring a child view in one dimension.

Parameters
int parentSize

Size of the parent view where the child will be placed

int parentMode

The measurement spec mode of the parent

int padding

Total space currently consumed by other elements of parent

int childDimension

Desired size of the child view, or MATCH_PARENT/WRAP_CONTENT. Generally obtained from the child view's LayoutParams

boolean canScroll

true if the parent RecyclerView can scroll in this dimension

Returns
int

a MeasureSpec value for the child view

getClipToPadding

Added in 1.0.0
public boolean getClipToPadding()

Check if the RecyclerView is configured to clip child views to its padding.

Returns
boolean

true if this RecyclerView clips children to its padding, false otherwise

getColumnCountForAccessibility

Added in 1.0.0
public int getColumnCountForAccessibility(
    @NonNull RecyclerView.Recycler recycler,
    @NonNull RecyclerView.State state
)

Returns the number of columns for accessibility.

Default implementation returns the number of items in the adapter if LayoutManager supports horizontal scrolling or 1 if LayoutManager does not support horizontal scrolling.

Parameters
@NonNull RecyclerView.Recycler recycler

The Recycler that can be used to convert view positions into adapter positions

@NonNull RecyclerView.State state

The current state of RecyclerView

Returns
int

The number of rows in LayoutManager for accessibility.

getDecoratedBottom

Added in 1.0.0
public int getDecoratedBottom(@NonNull View child)

Returns the bottom edge of the given child view within its parent, offset by any applied ItemDecorations.

Parameters
@NonNull View child

Child to query

Returns
int

Child bottom edge with offsets applied

getDecoratedBoundsWithMargins

Added in 1.0.0
public void getDecoratedBoundsWithMargins(@NonNull View view, @NonNull Rect outBounds)

Returns the bounds of the view including its decoration and margins.

Parameters
@NonNull View view

The view element to check

@NonNull Rect outBounds

A rect that will receive the bounds of the element including its decoration and margins.

getDecoratedLeft

Added in 1.0.0
public int getDecoratedLeft(@NonNull View child)

Returns the left edge of the given child view within its parent, offset by any applied ItemDecorations.

Parameters
@NonNull View child

Child to query

Returns
int

Child left edge with offsets applied

getDecoratedMeasuredHeight

Added in 1.0.0
public int getDecoratedMeasuredHeight(@NonNull View child)

Returns the measured height of the given child, plus the additional size of any insets applied by ItemDecorations.

Parameters
@NonNull View child

Child view to query

Returns
int

child's measured height plus ItemDecoration insets

getDecoratedMeasuredWidth

Added in 1.0.0
public int getDecoratedMeasuredWidth(@NonNull View child)

Returns the measured width of the given child, plus the additional size of any insets applied by ItemDecorations.

Parameters
@NonNull View child

Child view to query

Returns
int

child's measured width plus ItemDecoration insets

See also
getMeasuredWidth

getDecoratedRight

Added in 1.0.0
public int getDecoratedRight(@NonNull View child)

Returns the right edge of the given child view within its parent, offset by any applied ItemDecorations.

Parameters
@NonNull View child

Child to query

Returns
int

Child right edge with offsets applied

getDecoratedTop

Added in 1.0.0
public int getDecoratedTop(@NonNull View child)

Returns the top edge of the given child view within its parent, offset by any applied ItemDecorations.

Parameters
@NonNull View child

Child to query

Returns
int

Child top edge with offsets applied

getFocusedChild

Added in 1.0.0
public @Nullable View getFocusedChild()

Returns the item View which has or contains focus.

Returns
@Nullable View

A direct child of RecyclerView which has focus or contains the focused child.

getHeight

Added in 1.0.0
public @Px int getHeight()

Returns the height that is currently relevant to the LayoutManager.

This value is usually equal to the laid out height of the RecyclerView but may reflect the current android.view.View.MeasureSpec height if the LayoutManager is using AutoMeasure and the RecyclerView is in the process of measuring. The LayoutManager must always use this method to retrieve the height relevant to it at any given time.

Returns
@Px int

Height in pixels

getHeightMode

Added in 1.0.0
public int getHeightMode()

Return the height measurement spec mode that is currently relevant to the LayoutManager.

This value is set only if the LayoutManager opts into the AutoMeasure api via setAutoMeasureEnabled.

When RecyclerView is running a layout, this value is always set to EXACTLY even if it was measured with a different spec mode.

Returns
int

Height measure spec mode

See also
getMode

getItemCount

Added in 1.0.0
public int getItemCount()

Returns the number of items in the adapter bound to the parent RecyclerView.

Note that this number is not necessarily equal to State#getItemCount(). In methods where State is available, you should use State#getItemCount() instead. For more details, check the documentation for State#getItemCount().

Returns
int

The number of items in the bound adapter

See also
getItemCount

getItemViewType

Added in 1.0.0
public int getItemViewType(@NonNull View view)

Returns the View type defined by the adapter.

Parameters
@NonNull View view

The view to query

Returns
int

The type of the view assigned by the adapter.

getLayoutDirection

Added in 1.0.0
public int getLayoutDirection()

Returns the resolved layout direction for this RecyclerView.

Returns
int

LAYOUT_DIRECTION_RTL if the layout direction is RTL or returns LAYOUT_DIRECTION_LTR if the layout direction is not RTL.

getLeftDecorationWidth

Added in 1.0.0
public int getLeftDecorationWidth(@NonNull View child)

Returns the total width of item decorations applied to child's left.

Note that this value is not updated until the View is measured or calculateItemDecorationsForChild is called.

Parameters
@NonNull View child

Child to query

Returns
int

The total width of item decorations applied to the child's left.

getMinimumHeight

Added in 1.0.0
public @Px int getMinimumHeight()
Returns
@Px int

The host RecyclerView's getMinimumHeight

getMinimumWidth

Added in 1.0.0
public @Px int getMinimumWidth()
Returns
@Px int

The host RecyclerView's getMinimumWidth

getPaddingBottom

Added in 1.0.0
public @Px int getPaddingBottom()

Return the bottom padding of the parent RecyclerView

Returns
@Px int

Padding in pixels

getPaddingEnd

Added in 1.0.0
public @Px int getPaddingEnd()

Return the end padding of the parent RecyclerView

Returns
@Px int

Padding in pixels

getPaddingLeft

Added in 1.0.0
public @Px int getPaddingLeft()

Return the left padding of the parent RecyclerView

Returns
@Px int

Padding in pixels

getPaddingRight

Added in 1.0.0
public @Px int getPaddingRight()

Return the right padding of the parent RecyclerView

Returns
@Px int

Padding in pixels

getPaddingStart

Added in 1.0.0
public @Px int getPaddingStart()

Return the start padding of the parent RecyclerView

Returns
@Px int

Padding in pixels

getPaddingTop

Added in 1.0.0
public @Px int getPaddingTop()

Return the top padding of the parent RecyclerView

Returns
@Px int

Padding in pixels

getPosition

Added in 1.0.0
public int getPosition(@NonNull View view)

Returns the adapter position of the item represented by the given View. This does not contain any adapter changes that might have happened after the last layout.

Parameters
@NonNull View view

The view to query

Returns
int

The adapter position of the item which is rendered by this View.

getProperties

Added in 1.0.0
public static RecyclerView.LayoutManager.Properties getProperties(
    @NonNull Context context,
    @Nullable AttributeSet attrs,
    int defStyleAttr,
    int defStyleRes
)

Parse the xml attributes to get the most common properties used by layout managers. orientationspanCountreverseLayoutstackFromEnd

Returns
RecyclerView.LayoutManager.Properties

an object containing the properties as specified in the attrs.

getRightDecorationWidth

Added in 1.0.0
public int getRightDecorationWidth(@NonNull View child)

Returns the total width of item decorations applied to child's right.

Note that this value is not updated until the View is measured or calculateItemDecorationsForChild is called.

Parameters
@NonNull View child

Child to query

Returns
int

The total width of item decorations applied to the child's right.

getRowCountForAccessibility

Added in 1.0.0
public int getRowCountForAccessibility(
    @NonNull RecyclerView.Recycler recycler,
    @NonNull RecyclerView.State state
)

Returns the number of rows for accessibility.

Default implementation returns the number of items in the adapter if LayoutManager supports vertical scrolling or 1 if LayoutManager does not support vertical scrolling.

Parameters
@NonNull RecyclerView.Recycler recycler

The Recycler that can be used to convert view positions into adapter positions

@NonNull RecyclerView.State state

The current state of RecyclerView

Returns
int

The number of rows in LayoutManager for accessibility.

getSelectionModeForAccessibility

Added in 1.0.0
public int getSelectionModeForAccessibility(
    @NonNull RecyclerView.Recycler recycler,
    @NonNull RecyclerView.State state
)

Returns the selection mode for accessibility. Should be SELECTION_MODE_NONE, SELECTION_MODE_SINGLE or SELECTION_MODE_MULTIPLE.

Default implementation returns SELECTION_MODE_NONE.

Parameters
@NonNull RecyclerView.Recycler recycler

The Recycler that can be used to convert view positions into adapter positions

@NonNull RecyclerView.State state

The current state of RecyclerView

Returns
int

Selection mode for accessibility. Default implementation returns SELECTION_MODE_NONE.

getTopDecorationHeight

Added in 1.0.0
public int getTopDecorationHeight(@NonNull View child)

Returns the total height of item decorations applied to child's top.

Note that this value is not updated until the View is measured or calculateItemDecorationsForChild is called.

Parameters
@NonNull View child

Child to query

Returns
int

The total height of item decorations applied to the child's top.

getTransformedBoundingBox

Added in 1.0.0
public void getTransformedBoundingBox(
    @NonNull View child,
    boolean includeDecorInsets,
    @NonNull Rect out
)

Calculates the bounding box of the View while taking into account its matrix changes (translation, scale etc) with respect to the RecyclerView.

If includeDecorInsets is true, they are applied first before applying the View's matrix so that the decor offsets also go through the same transformation.

Parameters
@NonNull View child

The ItemView whose bounding box should be calculated.

boolean includeDecorInsets

True if the decor insets should be included in the bounding box

@NonNull Rect out

The rectangle into which the output will be written.

getWidth

Added in 1.0.0
public @Px int getWidth()

Returns the width that is currently relevant to the LayoutManager.

This value is usually equal to the laid out width of the RecyclerView but may reflect the current android.view.View.MeasureSpec width if the LayoutManager is using AutoMeasure and the RecyclerView is in the process of measuring. The LayoutManager must always use this method to retrieve the width relevant to it at any given time.

Returns
@Px int

Width in pixels

getWidthMode

Added in 1.0.0
public int getWidthMode()

Return the width measurement spec mode that is currently relevant to the LayoutManager.

This value is set only if the LayoutManager opts into the AutoMeasure api via setAutoMeasureEnabled.

When RecyclerView is running a layout, this value is always set to EXACTLY even if it was measured with a different spec mode.

Returns
int

Width measure spec mode

See also
getMode

hasFocus

Added in 1.0.0
public boolean hasFocus()

Returns true if the RecyclerView this LayoutManager is bound to has or contains focus.

Returns
boolean

true if the RecyclerView has or contains focus

See also
hasFocus

ignoreView

Added in 1.0.0
public void ignoreView(@NonNull View view)

Flags a view so that it will not be scrapped or recycled.

Scope of ignoring a child is strictly restricted to position tracking, scrapping and recyling. Methods like removeAndRecycleAllViews will ignore the child whereas removeAllViews or offsetChildrenHorizontal will not ignore the child.

Before this child can be recycled again, you have to call stopIgnoringView.

You can call this method only if your LayoutManger is in onLayout or onScroll callback.

Parameters
@NonNull View view

View to ignore.

See also
stopIgnoringView

isAttachedToWindow

Added in 1.0.0
public boolean isAttachedToWindow()

Returns whether LayoutManager is currently attached to a RecyclerView which is attached to a window.

Returns
boolean

True if this LayoutManager is controlling a RecyclerView and the RecyclerView is attached to window.

isAutoMeasureEnabled

Added in 1.0.0
public boolean isAutoMeasureEnabled()

Returns whether the measuring pass of layout should use the AutoMeasure mechanism of RecyclerView or if it should be done by the LayoutManager's implementation of onMeasure.

This method returns false by default (it actually returns the value passed to the deprecated setAutoMeasureEnabled) and should be overridden to return true if a LayoutManager wants to be auto measured by the RecyclerView.

If this method is overridden to return true, onMeasure should not be overridden.

AutoMeasure is a RecyclerView mechanism that handles the measuring pass of layout in a simple and contract satisfying way, including the wrapping of children laid out by LayoutManager. Simply put, it handles wrapping children by calling onLayoutChildren during a call to onMeasure, and then calculating desired dimensions based on children's dimensions and positions. It does this while supporting all existing animation capabilities of the RecyclerView.

More specifically:

  1. When onMeasure is called, if the provided measure specs both have a mode of EXACTLY, RecyclerView will set its measured dimensions accordingly and return, allowing layout to continue as normal (Actually, RecyclerView will call onMeasure for backwards compatibility reasons but it should not be overridden if AutoMeasure is being used).
  2. If one of the layout specs is not EXACT, the RecyclerView will start the layout process. It will first process all pending Adapter updates and then decide whether to run a predictive layout. If it decides to do so, it will first call onLayoutChildren with isPreLayout set to true. At this stage, getWidth and getHeight will still return the width and height of the RecyclerView as of the last layout calculation.

    After handling the predictive case, RecyclerView will call onLayoutChildren with isMeasuring set to true and isPreLayout set to false. The LayoutManager can access the measurement specs via getHeight, getHeightMode, getWidth and getWidthMode.

  3. After the layout calculation, RecyclerView sets the measured width &height by calculating the bounding box for the children (+ RecyclerView's padding). The LayoutManagers can override setMeasuredDimension to choose different values. For instance, GridLayoutManager overrides this value to handle the case where if it is vertical and has 3 columns but only 2 items, it should still measure its width to fit 3 items, not 2.
  4. Any following calls to onMeasure will run onLayoutChildren with isMeasuring set to true and isPreLayout set to false. RecyclerView will take care of which views are actually added / removed / moved / changed for animations so that the LayoutManager should not worry about them and handle each onLayoutChildren call as if it is the last one.
  5. When measure is complete and RecyclerView's onLayout method is called, RecyclerView checks whether it already did layout calculations during the measure pass and if so, it re-uses that information. It may still decide to call onLayoutChildren if the last measure spec was different from the final dimensions or adapter contents have changed between the measure call and the layout call.
  6. Finally, animations are calculated and run as usual.
Returns
boolean

True if the measuring pass of layout should use the AutoMeasure mechanism of RecyclerView or False if it should be done by the LayoutManager's implementation of onMeasure.

isFocused

Added in 1.0.0
public boolean isFocused()

Returns true if the RecyclerView this LayoutManager is bound to has focus.

Returns
boolean

True if the RecyclerView has focus, false otherwise.

See also
isFocused

isItemPrefetchEnabled

Added in 1.0.0
public final boolean isItemPrefetchEnabled()

Sets whether the LayoutManager should be queried for views outside of its viewport while the UI thread is idle between frames.

Returns
boolean

true if item prefetch is enabled, false otherwise

isLayoutHierarchical

Added in 1.0.0
public boolean isLayoutHierarchical(
    @NonNull RecyclerView.Recycler recycler,
    @NonNull RecyclerView.State state
)

Returns whether layout is hierarchical or not to be used for accessibility.

Default implementation returns false.

Parameters
@NonNull RecyclerView.Recycler recycler

The Recycler that can be used to convert view positions into adapter positions

@NonNull RecyclerView.State state

The current state of RecyclerView

Returns
boolean

True if layout is hierarchical.

isLayoutReversed

Added in 1.4.0-rc01
public boolean isLayoutReversed()

Query if the layout is in reverse order. This will affect, for example, keyboard navigation via page up/page down. The default implementation returns false.

Returns
boolean

true if this LayoutManager is currently in reverse order.

isMeasurementCacheEnabled

Added in 1.0.0
public boolean isMeasurementCacheEnabled()

In addition to the View Framework's measurement cache, RecyclerView uses its own additional measurement cache for its children to avoid re-measuring them when not necessary. It is on by default but it can be turned off via setMeasurementCacheEnabled.

Returns
boolean

True if measurement cache is enabled, false otherwise.

isSmoothScrolling

Added in 1.0.0
public boolean isSmoothScrolling()
Returns
boolean

true if RecyclerView is currently in the state of smooth scrolling.

isViewPartiallyVisible

Added in 1.0.0
public boolean isViewPartiallyVisible(
    @NonNull View child,
    boolean completelyVisible,
    boolean acceptEndPointInclusion
)

Returns whether the given child view is partially or fully visible within the padded bounded area of RecyclerView, depending on the input parameters. A view is partially visible if it has non-zero overlap with RV's padded bounded area. If acceptEndPointInclusion flag is set to true, it's also considered partially visible if it's located outside RV's bounds and it's hitting either RV's start or end bounds.

Parameters
@NonNull View child

The child view to be examined.

boolean completelyVisible

If true, the method returns true if and only if the child is completely visible. If false, the method returns true if and only if the child is only partially visible (that is it will return false if the child is either completely visible or out of RV's bounds).

boolean acceptEndPointInclusion

If the view's endpoint intersection with RV's start of end bounds is enough to consider it partially visible, false otherwise.

Returns
boolean

True if the given child is partially or fully visible, false otherwise.

layoutDecorated

Added in 1.0.0
public void layoutDecorated(
    @NonNull View child,
    int left,
    int top,
    int right,
    int bottom
)

Lay out the given child view within the RecyclerView using coordinates that include any current ItemDecorations.

LayoutManagers should prefer working in sizes and coordinates that include item decoration insets whenever possible. This allows the LayoutManager to effectively ignore decoration insets within measurement and layout code. See the following methods:

Parameters
@NonNull View child

Child to lay out

int left

Left edge, with item decoration insets included

int top

Top edge, with item decoration insets included

int right

Right edge, with item decoration insets included

int bottom

Bottom edge, with item decoration insets included

layoutDecoratedWithMargins

Added in 1.0.0
public void layoutDecoratedWithMargins(
    @NonNull View child,
    int left,
    int top,
    int right,
    int bottom
)

Lay out the given child view within the RecyclerView using coordinates that include any current ItemDecorations and margins.

LayoutManagers should prefer working in sizes and coordinates that include item decoration insets whenever possible. This allows the LayoutManager to effectively ignore decoration insets within measurement and layout code. See the following methods:

Parameters
@NonNull View child

Child to lay out

int left

Left edge, with item decoration insets and left margin included

int top

Top edge, with item decoration insets and top margin included

int right

Right edge, with item decoration insets and right margin included

int bottom

Bottom edge, with item decoration insets and bottom margin included

measureChild

Added in 1.0.0
public void measureChild(@NonNull View child, int widthUsed, int heightUsed)

Measure a child view using standard measurement policy, taking the padding of the parent RecyclerView and any added item decorations into account.

If the RecyclerView can be scrolled in either dimension the caller may pass 0 as the widthUsed or heightUsed parameters as they will be irrelevant.

Parameters
@NonNull View child

Child view to measure

int widthUsed

Width in pixels currently consumed by other views, if relevant

int heightUsed

Height in pixels currently consumed by other views, if relevant

measureChildWithMargins

Added in 1.0.0
public void measureChildWithMargins(
    @NonNull View child,
    int widthUsed,
    int heightUsed
)

Measure a child view using standard measurement policy, taking the padding of the parent RecyclerView, any added item decorations and the child margins into account.

If the RecyclerView can be scrolled in either dimension the caller may pass 0 as the widthUsed or heightUsed parameters as they will be irrelevant.

Parameters
@NonNull View child

Child view to measure

int widthUsed

Width in pixels currently consumed by other views, if relevant

int heightUsed

Height in pixels currently consumed by other views, if relevant

moveView

Added in 1.0.0
public void moveView(int fromIndex, int toIndex)

Moves a View from one position to another.

Parameters
int fromIndex

The View's initial index

int toIndex

The View's target index

offsetChildrenHorizontal

Added in 1.0.0
public void offsetChildrenHorizontal(@Px int dx)

Offset all child views attached to the parent RecyclerView by dx pixels along the horizontal axis.

Parameters
@Px int dx

Pixels to offset by

offsetChildrenVertical

Added in 1.0.0
public void offsetChildrenVertical(@Px int dy)

Offset all child views attached to the parent RecyclerView by dy pixels along the vertical axis.

Parameters
@Px int dy

Pixels to offset by

onAdapterChanged

Added in 1.0.0
public void onAdapterChanged(
    @Nullable RecyclerView.Adapter oldAdapter,
    @Nullable RecyclerView.Adapter newAdapter
)

Called if the RecyclerView this LayoutManager is bound to has a different adapter set via setAdapter or swapAdapter. The LayoutManager may use this opportunity to clear caches and configure state such that it can relayout appropriately with the new data and potentially new view types.

The default implementation removes all currently attached views.

Parameters
@Nullable RecyclerView.Adapter oldAdapter

The previous adapter instance. Will be null if there was previously no adapter.

@Nullable RecyclerView.Adapter newAdapter

The new adapter instance. Might be null if setAdapter is called with null.

onAddFocusables

Added in 1.0.0
public boolean onAddFocusables(
    @NonNull RecyclerView recyclerView,
    @NonNull ArrayList<View> views,
    int direction,
    int focusableMode
)

Called to populate focusable views within the RecyclerView.

The LayoutManager implementation should return true if the default behavior of addFocusables should be suppressed.

The default implementation returns false to trigger RecyclerView to fall back to the default ViewGroup behavior.

Parameters
@NonNull RecyclerView recyclerView

The RecyclerView hosting this LayoutManager

@NonNull ArrayList<View> views

List of output views. This method should add valid focusable views to this list.

int direction

One of FOCUS_UP, FOCUS_DOWN, FOCUS_LEFT, FOCUS_RIGHT, FOCUS_BACKWARD, FOCUS_FORWARD

int focusableMode

The type of focusables to be added.

Returns
boolean

true to suppress the default behavior, false to add default focusables after this method returns.

onAttachedToWindow

Added in 1.0.0
@CallSuper
public void onAttachedToWindow(RecyclerView view)

Called when this LayoutManager is both attached to a RecyclerView and that RecyclerView is attached to a window.

If the RecyclerView is re-attached with the same LayoutManager and Adapter, it may not call onLayoutChildren if nothing has changed and a layout was not requested on the RecyclerView while it was detached.

Subclass implementations should always call through to the superclass implementation.

Parameters
RecyclerView view

The RecyclerView this LayoutManager is bound to

onDetachedFromWindow

Added in 1.0.0
Deprecated in 1.0.0
public void onDetachedFromWindow(RecyclerView view)

onDetachedFromWindow

Added in 1.0.0
@CallSuper
public void onDetachedFromWindow(RecyclerView view, RecyclerView.Recycler recycler)

Called when this LayoutManager is detached from its parent RecyclerView or when its parent RecyclerView is detached from its window.

LayoutManager should clear all of its View references as another LayoutManager might be assigned to the RecyclerView.

If the RecyclerView is re-attached with the same LayoutManager and Adapter, it may not call onLayoutChildren if nothing has changed and a layout was not requested on the RecyclerView while it was detached.

If your LayoutManager has View references that it cleans in on-detach, it should also call requestLayout to ensure that it is re-laid out when RecyclerView is re-attached.

Subclass implementations should always call through to the superclass implementation.

Parameters
RecyclerView view

The RecyclerView this LayoutManager is bound to

RecyclerView.Recycler recycler

The recycler to use if you prefer to recycle your children instead of keeping them around.

onFocusSearchFailed

Added in 1.0.0
public @Nullable View onFocusSearchFailed(
    @NonNull View focused,
    int direction,
    @NonNull RecyclerView.Recycler recycler,
    @NonNull RecyclerView.State state
)

Called when searching for a focusable view in the given direction has failed for the current content of the RecyclerView.

This is the LayoutManager's opportunity to populate views in the given direction to fulfill the request if it can. The LayoutManager should attach and return the view to be focused, if a focusable view in the given direction is found. Otherwise, if all the existing (or the newly populated views) are unfocusable, it returns the next unfocusable view to become visible on the screen. This unfocusable view is typically the first view that's either partially or fully out of RV's padded bounded area in the given direction. The default implementation returns null.

Parameters
@NonNull View focused

The currently focused view

int direction

One of FOCUS_UP, FOCUS_DOWN, FOCUS_LEFT, FOCUS_RIGHT, FOCUS_BACKWARD, FOCUS_FORWARD or 0 for not applicable

@NonNull RecyclerView.Recycler recycler

The recycler to use for obtaining views for currently offscreen items

@NonNull RecyclerView.State state

Transient state of RecyclerView

Returns
@Nullable View

The chosen view to be focused if a focusable view is found, otherwise an unfocusable view to become visible onto the screen, else null.

onInitializeAccessibilityEvent

Added in 1.0.0
public void onInitializeAccessibilityEvent(@NonNull AccessibilityEvent event)

onInitializeAccessibilityEvent

Added in 1.0.0
public void onInitializeAccessibilityEvent(
    @NonNull RecyclerView.Recycler recycler,
    @NonNull RecyclerView.State state,
    @NonNull AccessibilityEvent event
)

Called by the accessibility delegate to initialize an accessibility event.

Default implementation adds item count and scroll information to the event.

Parameters
@NonNull RecyclerView.Recycler recycler

The Recycler that can be used to convert view positions into adapter positions

@NonNull RecyclerView.State state

The current state of RecyclerView

@NonNull AccessibilityEvent event

The event instance to initialize

onInitializeAccessibilityNodeInfo

Added in 1.0.0
public void onInitializeAccessibilityNodeInfo(
    @NonNull RecyclerView.Recycler recycler,
    @NonNull RecyclerView.State state,
    @NonNull AccessibilityNodeInfoCompat info
)

Called by the AccessibilityDelegate when the information about the current layout should be populated.

Default implementation adds a .

You should override getRowCountForAccessibility, getColumnCountForAccessibility, isLayoutHierarchical and getSelectionModeForAccessibility for more accurate accessibility information.

Parameters
@NonNull RecyclerView.Recycler recycler

The Recycler that can be used to convert view positions into adapter positions

@NonNull RecyclerView.State state

The current state of RecyclerView

@NonNull AccessibilityNodeInfoCompat info

The info that should be filled by the LayoutManager

onInitializeAccessibilityNodeInfoForItem

Added in 1.0.0
public void onInitializeAccessibilityNodeInfoForItem(
    @NonNull RecyclerView.Recycler recycler,
    @NonNull RecyclerView.State state,
    @NonNull View host,
    @NonNull AccessibilityNodeInfoCompat info
)

Called by the AccessibilityDelegate when the accessibility information for a specific item should be populated.

Default implementation adds basic positioning information about the item.

Parameters
@NonNull RecyclerView.Recycler recycler

The Recycler that can be used to convert view positions into adapter positions

@NonNull RecyclerView.State state

The current state of RecyclerView

@NonNull View host

The child for which accessibility node info should be populated

@NonNull AccessibilityNodeInfoCompat info

The info to fill out about the item

onInterceptFocusSearch

Added in 1.0.0
public @Nullable View onInterceptFocusSearch(@NonNull View focused, int direction)

This method gives a LayoutManager an opportunity to intercept the initial focus search before the default behavior of FocusFinder is used. If this method returns null FocusFinder will attempt to find a focusable child view. If it fails then onFocusSearchFailed will be called to give the LayoutManager an opportunity to add new views for items that did not have attached views representing them. The LayoutManager should not add or remove views from this method.

Parameters
@NonNull View focused

The currently focused view

int direction

One of FOCUS_UP, FOCUS_DOWN, FOCUS_LEFT, FOCUS_RIGHT, FOCUS_BACKWARD, FOCUS_FORWARD

Returns
@Nullable View

A descendant view to focus or null to fall back to default behavior. The default implementation returns null.

onItemsAdded

Added in 1.0.0
public void onItemsAdded(
    @NonNull RecyclerView recyclerView,
    int positionStart,
    int itemCount
)

Called when items have been added to the adapter. The LayoutManager may choose to requestLayout if the inserted items would require refreshing the currently visible set of child views. (e.g. currently empty space would be filled by appended items, etc.)

onItemsChanged

Added in 1.0.0
public void onItemsChanged(@NonNull RecyclerView recyclerView)

Called in response to a call to notifyDataSetChanged or swapAdapter ()} and signals that the the entire data set has changed.

onItemsMoved

Added in 1.0.0
public void onItemsMoved(
    @NonNull RecyclerView recyclerView,
    int from,
    int to,
    int itemCount
)

Called when an item is moved withing the adapter.

Note that, an item may also change position in response to another ADD/REMOVE/MOVE operation. This callback is only called if and only if notifyItemMoved is called.

onItemsRemoved

Added in 1.0.0
public void onItemsRemoved(
    @NonNull RecyclerView recyclerView,
    int positionStart,
    int itemCount
)

Called when items have been removed from the adapter.

onItemsUpdated

Added in 1.0.0
public void onItemsUpdated(
    @NonNull RecyclerView recyclerView,
    int positionStart,
    int itemCount
)

Called when items have been changed in the adapter. To receive payload, override onItemsUpdated instead, then this callback will not be invoked.

onItemsUpdated

Added in 1.0.0
public void onItemsUpdated(
    @NonNull RecyclerView recyclerView,
    int positionStart,
    int itemCount,
    @Nullable Object payload
)

Called when items have been changed in the adapter and with optional payload. Default implementation calls onItemsUpdated.

onLayoutChildren

Added in 1.0.0
public void onLayoutChildren(
    RecyclerView.Recycler recycler,
    RecyclerView.State state
)

Lay out all relevant child views from the given adapter. The LayoutManager is in charge of the behavior of item animations. By default, RecyclerView has a non-null ItemAnimator, and simple item animations are enabled. This means that add/remove operations on the adapter will result in animations to add new or appearing items, removed or disappearing items, and moved items. If a LayoutManager returns false from supportsPredictiveItemAnimations, which is the default, and runs a normal layout operation during onLayoutChildren, the RecyclerView will have enough information to run those animations in a simple way. For example, the default ItemAnimator, DefaultItemAnimator, will simply fade views in and out, whether they are actually added/removed or whether they are moved on or off the screen due to other add/remove operations.

A LayoutManager wanting a better item animation experience, where items can be animated onto and off of the screen according to where the items exist when they are not on screen, then the LayoutManager should return true from supportsPredictiveItemAnimations and add additional logic to onLayoutChildren. Supporting predictive animations means that onLayoutChildren will be called twice; once as a "pre" layout step to determine where items would have been prior to a real layout, and again to do the "real" layout. In the pre-layout phase, items will remember their pre-layout positions to allow them to be laid out appropriately. Also, removed items will be returned from the scrap to help determine correct placement of other items. These removed items should not be added to the child list, but should be used to help calculate correct positioning of other views, including views that were not previously onscreen (referred to as APPEARING views), but whose pre-layout offscreen position can be determined given the extra information about the pre-layout removed views.

The second layout pass is the real layout in which only non-removed views will be used. The only additional requirement during this pass is, if supportsPredictiveItemAnimations returns true, to note which views exist in the child list prior to layout and which are not there after layout (referred to as DISAPPEARING views), and to position/layout those views appropriately, without regard to the actual bounds of the RecyclerView. This allows the animation system to know the location to which to animate these disappearing views.

The default LayoutManager implementations for RecyclerView handle all of these requirements for animations already. Clients of RecyclerView can either use one of these layout managers directly or look at their implementations of onLayoutChildren() to see how they account for the APPEARING and DISAPPEARING views.

Parameters
RecyclerView.Recycler recycler

Recycler to use for fetching potentially cached views for a position

RecyclerView.State state

Transient state of RecyclerView

onLayoutCompleted

Added in 1.0.0
public void onLayoutCompleted(RecyclerView.State state)

Called after a full layout calculation is finished. The layout calculation may include multiple onLayoutChildren calls due to animations or layout measurement but it will include only one onLayoutCompleted call. This method will be called at the end of layout call.

This is a good place for the LayoutManager to do some cleanup like pending scroll position, saved state etc.

Parameters
RecyclerView.State state

Transient state of RecyclerView

onMeasure

Added in 1.0.0
public void onMeasure(
    @NonNull RecyclerView.Recycler recycler,
    @NonNull RecyclerView.State state,
    int widthSpec,
    int heightSpec
)

Measure the attached RecyclerView. Implementations must call setMeasuredDimension before returning.

It is strongly advised to use the AutoMeasure mechanism by overriding isAutoMeasureEnabled to return true as AutoMeasure handles all the standard measure cases including when the RecyclerView's layout_width or layout_height have been set to wrap_content. If isAutoMeasureEnabled is overridden to return true, this method should not be overridden.

The default implementation will handle EXACTLY measurements and respect the minimum width and height properties of the host RecyclerView if measured as UNSPECIFIED. AT_MOST measurements will be treated as EXACTLY and the RecyclerView will consume all available space.

Parameters
@NonNull RecyclerView.Recycler recycler

Recycler

@NonNull RecyclerView.State state

Transient state of RecyclerView

int widthSpec

Width android.view.View.MeasureSpec

int heightSpec

Height android.view.View.MeasureSpec

onRequestChildFocus

Added in 1.0.0
Deprecated in 1.0.0
public boolean onRequestChildFocus(
    @NonNull RecyclerView parent,
    @NonNull View child,
    @Nullable View focused
)

onRequestChildFocus

Added in 1.0.0
public boolean onRequestChildFocus(
    @NonNull RecyclerView parent,
    @NonNull RecyclerView.State state,
    @NonNull View child,
    @Nullable View focused
)

Called when a descendant view of the RecyclerView requests focus.

A LayoutManager wishing to keep focused views aligned in a specific portion of the view may implement that behavior in an override of this method.

If the LayoutManager executes different behavior that should override the default behavior of scrolling the focused child on screen instead of running alongside it, this method should return true.

Parameters
@NonNull RecyclerView parent

The RecyclerView hosting this LayoutManager

@NonNull RecyclerView.State state

Current state of RecyclerView

@NonNull View child

Direct child of the RecyclerView containing the newly focused view

@Nullable View focused

The newly focused view. This may be the same view as child or it may be null

Returns
boolean

true if the default scroll behavior should be suppressed

onRestoreInstanceState

Added in 1.0.0
public void onRestoreInstanceState(Parcelable state)

Called when the RecyclerView is ready to restore the state based on a previous RecyclerView. Notice that this might happen after an actual layout, based on how Adapter prefers to restore State. See getStateRestorationPolicy for more information.

Parameters
Parcelable state

The parcelable that was returned by the previous LayoutManager's onSaveInstanceState method.

onSaveInstanceState

Added in 1.0.0
public @Nullable Parcelable onSaveInstanceState()

Called when the LayoutManager should save its state. This is a good time to save your scroll position, configuration and anything else that may be required to restore the same layout state if the LayoutManager is recreated.

RecyclerView does NOT verify if the LayoutManager has changed between state save and restore. This will let you share information between your LayoutManagers but it is also your responsibility to make sure they use the same parcelable class.

Returns
@Nullable Parcelable

Necessary information for LayoutManager to be able to restore its state

onScrollStateChanged

Added in 1.0.0
public void onScrollStateChanged(int state)

RecyclerView calls this method to notify LayoutManager that scroll state has changed.

Parameters
int state

The new scroll state for RecyclerView

performAccessibilityAction

Added in 1.0.0
public boolean performAccessibilityAction(
    @NonNull RecyclerView.Recycler recycler,
    @NonNull RecyclerView.State state,
    int action,
    @Nullable Bundle args
)

Called by AccessibilityDelegate when an action is requested from the RecyclerView.

Parameters
@NonNull RecyclerView.Recycler recycler

The Recycler that can be used to convert view positions into adapter positions

@NonNull RecyclerView.State state

The current state of RecyclerView

int action

The action to perform

@Nullable Bundle args

Optional action arguments

performAccessibilityActionForItem

Added in 1.0.0
public boolean performAccessibilityActionForItem(
    @NonNull RecyclerView.Recycler recycler,
    @NonNull RecyclerView.State state,
    @NonNull View view,
    int action,
    @Nullable Bundle args
)

Called by AccessibilityDelegate when an accessibility action is requested on one of the children of LayoutManager.

Default implementation does not do anything.

Parameters
@NonNull RecyclerView.Recycler recycler

The Recycler that can be used to convert view positions into adapter positions

@NonNull RecyclerView.State state

The current state of RecyclerView

@NonNull View view

The child view on which the action is performed

int action

The action to perform

@Nullable Bundle args

Optional action arguments

Returns
boolean

true if action is handled

postOnAnimation

Added in 1.0.0
public void postOnAnimation(Runnable action)

Causes the Runnable to execute on the next animation time step. The runnable will be run on the user interface thread.

Calling this method when LayoutManager is not attached to a RecyclerView has no effect.

Parameters
Runnable action

The Runnable that will be executed.

See also
removeCallbacks

removeAllViews

Added in 1.0.0
public void removeAllViews()

Remove all views from the currently attached RecyclerView. This will not recycle any of the affected views; the LayoutManager is responsible for doing so if desired.

removeAndRecycleAllViews

Added in 1.0.0
public void removeAndRecycleAllViews(@NonNull RecyclerView.Recycler recycler)

Removes all views and recycles them using the given recycler.

If you want to clean cached views as well, you should call clear too.

If a View is marked as "ignored", it is not removed nor recycled.

Parameters
@NonNull RecyclerView.Recycler recycler

Recycler to use to recycle children

removeAndRecycleView

Added in 1.0.0
public void removeAndRecycleView(
    @NonNull View child,
    @NonNull RecyclerView.Recycler recycler
)

Remove a child view and recycle it using the given Recycler.

Parameters
@NonNull View child

Child to remove and recycle

@NonNull RecyclerView.Recycler recycler

Recycler to use to recycle child

removeAndRecycleViewAt

Added in 1.0.0
public void removeAndRecycleViewAt(
    int index,
    @NonNull RecyclerView.Recycler recycler
)

Remove a child view and recycle it using the given Recycler.

Parameters
int index

Index of child to remove and recycle

@NonNull RecyclerView.Recycler recycler

Recycler to use to recycle child

removeCallbacks

Added in 1.0.0
public boolean removeCallbacks(Runnable action)

Removes the specified Runnable from the message queue.

Calling this method when LayoutManager is not attached to a RecyclerView has no effect.

Parameters
Runnable action

The Runnable to remove from the message handling queue

Returns
boolean

true if RecyclerView could ask the Handler to remove the Runnable, false otherwise. When the returned value is true, the Runnable may or may not have been actually removed from the message queue (for instance, if the Runnable was not in the queue already.)

See also
postOnAnimation

removeDetachedView

Added in 1.0.0
public void removeDetachedView(@NonNull View child)

Finish removing a view that was previously temporarily detached.

Parameters
@NonNull View child

Detached child to remove

removeView

Added in 1.0.0
public void removeView(View child)

Remove a view from the currently attached RecyclerView if needed. LayoutManagers should use this method to completely remove a child view that is no longer needed. LayoutManagers should strongly consider recycling removed views using recycleView.

Parameters
View child

View to remove

removeViewAt

Added in 1.0.0
public void removeViewAt(int index)

Remove a view from the currently attached RecyclerView if needed. LayoutManagers should use this method to completely remove a child view that is no longer needed. LayoutManagers should strongly consider recycling removed views using recycleView.

Parameters
int index

Index of the child view to remove

requestChildRectangleOnScreen

Added in 1.0.0
public boolean requestChildRectangleOnScreen(
    @NonNull RecyclerView parent,
    @NonNull View child,
    @NonNull Rect rect,
    boolean immediate
)

Called when a child of the RecyclerView wants a particular rectangle to be positioned onto the screen. See requestChildRectangleOnScreen for more details.

The base implementation will attempt to perform a standard programmatic scroll to bring the given rect into view, within the padded area of the RecyclerView.

Parameters
@NonNull RecyclerView parent

The parent RecyclerView.

@NonNull View child

The direct child making the request.

@NonNull Rect rect

The rectangle in the child's coordinates the child wishes to be on the screen.

boolean immediate

True to forbid animated or delayed scrolling, false otherwise

Returns
boolean

Whether the group scrolled to handle the operation

requestChildRectangleOnScreen

Added in 1.0.0
public boolean requestChildRectangleOnScreen(
    @NonNull RecyclerView parent,
    @NonNull View child,
    @NonNull Rect rect,
    boolean immediate,
    boolean focusedChildVisible
)

Requests that the given child of the RecyclerView be positioned onto the screen. This method can be called for both unfocusable and focusable child views. For unfocusable child views, focusedChildVisible is typically true in which case, layout manager makes the child view visible only if the currently focused child stays in-bounds of RV.

Parameters
@NonNull RecyclerView parent

The parent RecyclerView.

@NonNull View child

The direct child making the request.

@NonNull Rect rect

The rectangle in the child's coordinates the child wishes to be on the screen.

boolean immediate

True to forbid animated or delayed scrolling, false otherwise

boolean focusedChildVisible

Whether the currently focused view must stay visible.

Returns
boolean

Whether the group scrolled to handle the operation

requestLayout

Added in 1.0.0
public void requestLayout()

Calls RecyclerView#requestLayout on the underlying RecyclerView

requestSimpleAnimationsInNextLayout

Added in 1.0.0
public void requestSimpleAnimationsInNextLayout()

A LayoutManager can call this method to force RecyclerView to run simple animations in the next layout pass, even if there is not any trigger to do so. (e.g. adapter data change).

Note that, calling this method will not guarantee that RecyclerView will run animations at all. For example, if there is not any ItemAnimator set, RecyclerView will not run any animations but will still clear this flag after the layout is complete.

scrollHorizontallyBy

Added in 1.0.0
public int scrollHorizontallyBy(
    int dx,
    RecyclerView.Recycler recycler,
    RecyclerView.State state
)

Scroll horizontally by dx pixels in screen coordinates and return the distance traveled. The default implementation does nothing and returns 0.

Parameters
int dx

distance to scroll by in pixels. X increases as scroll position approaches the right.

RecyclerView.Recycler recycler

Recycler to use for fetching potentially cached views for a position

RecyclerView.State state

Transient state of RecyclerView

Returns
int

The actual distance scrolled. The return value will be negative if dx was negative and scrolling proceeeded in that direction. Math.abs(result) may be less than dx if a boundary was reached.

scrollToPosition

Added in 1.0.0
public void scrollToPosition(int position)

Scroll to the specified adapter position. Actual position of the item on the screen depends on the LayoutManager implementation.

Parameters
int position

Scroll to this adapter position.

scrollVerticallyBy

Added in 1.0.0
public int scrollVerticallyBy(
    int dy,
    RecyclerView.Recycler recycler,
    RecyclerView.State state
)

Scroll vertically by dy pixels in screen coordinates and return the distance traveled. The default implementation does nothing and returns 0.

Parameters
int dy

distance to scroll in pixels. Y increases as scroll position approaches the bottom.

RecyclerView.Recycler recycler

Recycler to use for fetching potentially cached views for a position

RecyclerView.State state

Transient state of RecyclerView

Returns
int

The actual distance scrolled. The return value will be negative if dy was negative and scrolling proceeeded in that direction. Math.abs(result) may be less than dy if a boundary was reached.

setAutoMeasureEnabled

Added in 1.0.0
Deprecated in 1.0.0
public void setAutoMeasureEnabled(boolean enabled)

Defines whether the measuring pass of layout should use the AutoMeasure mechanism of RecyclerView or if it should be done by the LayoutManager's implementation of onMeasure.

Parameters
boolean enabled

True if layout measurement should be done by the RecyclerView, false if it should be done by this LayoutManager.

setItemPrefetchEnabled

Added in 1.0.0
public final void setItemPrefetchEnabled(boolean enabled)

Sets whether the LayoutManager should be queried for views outside of its viewport while the UI thread is idle between frames.

If enabled, the LayoutManager will be queried for items to inflate/bind in between view system traversals on devices running API 21 or greater. Default value is true.

On platforms API level 21 and higher, the UI thread is idle between passing a frame to RenderThread and the starting up its next frame at the next VSync pulse. By prefetching out of window views in this time period, delays from inflation and view binding are much less likely to cause jank and stuttering during scrolls and flings.

While prefetch is enabled, it will have the side effect of expanding the effective size of the View cache to hold prefetched views.

Parameters
boolean enabled

True if items should be prefetched in between traversals.

setMeasuredDimension

Added in 1.0.0
public void setMeasuredDimension(int widthSize, int heightSize)

Set the measured dimensions of the host RecyclerView.

Parameters
int widthSize

Measured width

int heightSize

Measured height

setMeasuredDimension

Added in 1.0.0
public void setMeasuredDimension(Rect childrenBounds, int wSpec, int hSpec)

Sets the measured dimensions from the given bounding box of the children and the measurement specs that were passed into onMeasure. It is only called if a LayoutManager returns true from isAutoMeasureEnabled and it is called after the RecyclerView calls onLayoutChildren in the execution of onMeasure.

This method must call setMeasuredDimension.

The default implementation adds the RecyclerView's padding to the given bounding box then caps the value to be within the given measurement specs.

Parameters
Rect childrenBounds

The bounding box of all children

int wSpec

The widthMeasureSpec that was passed into the RecyclerView.

int hSpec

The heightMeasureSpec that was passed into the RecyclerView.

setMeasurementCacheEnabled

Added in 1.0.0
public void setMeasurementCacheEnabled(boolean measurementCacheEnabled)

Sets whether RecyclerView should use its own measurement cache for the children. This is a more aggressive cache than the framework uses.

Parameters
boolean measurementCacheEnabled

True to enable the measurement cache, false otherwise.

smoothScrollToPosition

Added in 1.0.0
public void smoothScrollToPosition(
    RecyclerView recyclerView,
    RecyclerView.State state,
    int position
)

Smooth scroll to the specified adapter position.

To support smooth scrolling, override this method, create your SmoothScroller instance and call startSmoothScroll.

Parameters
RecyclerView recyclerView

The RecyclerView to which this layout manager is attached

RecyclerView.State state

Current State of RecyclerView

int position

Scroll to this adapter position.

startSmoothScroll

Added in 1.0.0
public void startSmoothScroll(RecyclerView.SmoothScroller smoothScroller)

Starts a smooth scroll using the provided SmoothScroller.

Each instance of SmoothScroller is intended to only be used once. Provide a new SmoothScroller instance each time this method is called.

Calling this method will cancel any previous smooth scroll request.

Parameters
RecyclerView.SmoothScroller smoothScroller

Instance which defines how smooth scroll should be animated

stopIgnoringView

Added in 1.0.0
public void stopIgnoringView(@NonNull View view)

View can be scrapped and recycled again.

Note that calling this method removes all information in the view holder.

You can call this method only if your LayoutManger is in onLayout or onScroll callback.

Parameters
@NonNull View view

View to ignore.

supportsPredictiveItemAnimations

Added in 1.0.0
public boolean supportsPredictiveItemAnimations()

Returns whether this LayoutManager supports "predictive item animations".

"Predictive item animations" are automatically created animations that show where items came from, and where they are going to, as items are added, removed, or moved within a layout.

A LayoutManager wishing to support predictive item animations must override this method to return true (the default implementation returns false) and must obey certain behavioral contracts outlined in onLayoutChildren.

Whether item animations actually occur in a RecyclerView is actually determined by both the return value from this method and the ItemAnimator set on the RecyclerView itself. If the RecyclerView has a non-null ItemAnimator but this method returns false, then only "simple item animations" will be enabled in the RecyclerView, in which views whose position are changing are simply faded in/out. If the RecyclerView has a non-null ItemAnimator and this method returns true, then predictive item animations will be enabled in the RecyclerView.

Returns
boolean

true if this LayoutManager supports predictive item animations, false otherwise.