Use window size classes

Window size classes are a set of opinionated viewport breakpoints that help you design, develop, and test responsive/adaptive layouts. The breakpoints balance layout simplicity with the flexibility of optimizing your app for unique cases.

Window size classes categorize the display area available to your app as compact, medium, or expanded. Available width and height are classified separately, so at any point in time, your app has two window size classes—one for width, one for height. Available width is usually more important than available height due to the ubiquity of vertical scrolling, so the width window size class is likely more relevant to your app's UI.

**Figure 1.** Representations of width-based window size classes.

**Figure 2.** Representations of height-based window size classes.

As visualized in the figures, the breakpoints allow you to continue thinking about layouts in terms of devices and configurations. Each size class breakpoint represents a majority case for typical device scenarios, which can be a helpful frame of reference as you think about the design of your breakpoint-based layouts.

Size class	Breakpoint	Device representation
Compact width	width < 600dp	99.96% of phones in portrait
Medium width	600dp ≤ width < 840dp	93.73% of tablets in portrait, most large unfolded inner displays in portrait
Expanded width	width ≥ 840dp	97.22% of tablets in landscape, most large unfolded inner displays in landscape
Compact height	height < 480dp	99.78% of phones in landscape
Medium height	480dp ≤ height < 900dp	96.56% of tablets in landscape, 97.59% of phones in portrait
Expanded height	height ≥ 900dp	94.25% of tablets in portrait

Although visualizing size classes as physical devices can be useful, window size classes are explicitly not determined by the size of the device screen. Window size classes are not intended for isTablet‑type logic. Rather, window size classes are determined by the window size available to your application regardless of the type of device the app is running on, which has two important implications:

Physical devices do not guarantee a specific window size class. The screen space available to your app can differ from the screen size of the device for many reasons. On mobile devices, split‑screen mode can partition the screen between two applications. On ChromeOS, Android apps can be presented in desktop‑type windows that are arbitrarily resizable. Foldables can have two different‑sized screens individually accessed by folding or unfolding the device.
The window size class can change throughout the lifetime of your app. While your app is running, device orientation changes, multitasking, and folding/unfolding can change the amount of screen space available. As a result, the window size class is dynamic, and your app's UI should adapt accordingly.

Window size classes map to the compact, medium, and expanded breakpoints in the Material Design layout guidance. Use window size classes to make high‑level application layout decisions, such as deciding whether to use a specific canonical layout to take advantage of additional screen space.

使用WindowSizeClass currentWindowAdaptiveInfo() 的顶层函数 androidx.compose.material3.adaptive 库。该函数返回一个 WindowAdaptiveInfo 的实例，其中包含 windowSizeClass。通过以下示例展示了如何计算窗口大小类别并接收会在窗口大小类别发生变化时更新：

val windowSizeClass = currentWindowAdaptiveInfo().windowSizeClassAdaptiveLayoutSnippets.kt

使用窗口大小类别管理布局

通过窗口大小类别，您可以将应用布局更改为显示空间更改，例如当设备折叠或展开时，设备屏幕方向发生变化，或者应用窗口在多窗口模式下被调整大小模式。

通过传递窗口大小，将用于处理显示屏大小变化的逻辑本地化像任何其他应用状态一样，将类作为状态向下传递到嵌套可组合项：

@OptIn(ExperimentalMaterial3AdaptiveApi::class)
@Composable
fun MyApp(
    windowSizeClass: WindowSizeClass = currentWindowAdaptiveInfo().windowSizeClass
) {
    // Perform logic on the size class to decide whether to show the top app bar.
    val showTopAppBar = windowSizeClass.windowHeightSizeClass != WindowHeightSizeClass.COMPACT

    // MyScreen knows nothing about window sizes, and performs logic based on a Boolean flag.
    MyScreen(
        showTopAppBar = showTopAppBar,
        /* ... */
    )
}AdaptiveLayoutSnippets.kt

Test window size classes

As you make layout changes, test the layout behavior across all window sizes, especially at the compact, medium, and expanded breakpoint widths.

If you have an existing layout for compact screens, first optimize your layout for the expanded width size class, since this size class provides the most space for additional content and UI changes. Then decide what layout makes sense for the medium width size class; consider adding a specialized layout.

Next steps

To learn more about how to use window size classes to create responsive/adaptive layouts, see the following:

For Compose-based layouts: Support different screen sizes
For view-based layouts: Responsive/adaptive design with views

To learn more about what makes an app great on all devices and screen sizes, see:

Support different screen sizes

Support multi-window mode