Integrate asset delivery (Kotlin & Java)

Use the steps in this guide to access your app’s asset packs from your Java code.

Build for Kotlin & Java

Use the following steps to build Play Asset Delivery into your project’s Android App Bundle. You don't need to use Android Studio to perform these steps.

  1. Update the version of the Android Gradle plugin in your project’s build.gradle file to 4.0.0 or later.

  2. In the top-level directory of your project, create a directory for the asset pack. This directory name is used as the asset pack name. Asset pack names must start with a letter and can only contain letters, numbers, and underscores.

  3. In the asset pack directory, create a build.gradle file and add the following code. Make sure to specify the name of the asset pack and only one delivery type:

    Groovy

    // In the asset pack’s build.gradle file:
plugins {
  id 'com.android.asset-pack'
}

assetPack {
    packName = "asset-pack-name" // Directory name for the asset pack
    dynamicDelivery {
        deliveryType = "[ install-time | fast-follow | on-demand ]"
    }
}

    Kotlin

    // In the asset pack’s build.gradle.kts file:
plugins {
  id("com.android.asset-pack")
}

assetPack {
  packName.set("asset-pack-name") // Directory name for the asset pack
  dynamicDelivery {
    deliveryType.set("[ install-time | fast-follow | on-demand ]")
  }
}

  4. In the project’s app build.gradle file, add the name of every asset pack in your project as shown below:

    Groovy

    // In the app build.gradle file:
android {
    ...
    assetPacks = [":asset-pack-name", ":asset-pack2-name"]
}

    Kotlin

    // In the app build.gradle.kts file:
android {
    ...
    assetPacks += listOf(":asset-pack-name", ":asset-pack2-name")
}

  5. In the project’s settings.gradle file, include all asset packs in your project as shown below:

    Groovy

    // In the settings.gradle file:
include ':app'
include ':asset-pack-name'
include ':asset-pack2-name'

    Kotlin

    // In the settings.gradle.kts file:
include(":app")
include(":asset-pack-name")
include(":asset-pack2-name")

  6. In the asset pack directory, create the following subdirectory: src/main/assets.

  7. Place assets in the src/main/assets directory. You can create subdirectories in here as well. The directory structure for your app should now look like the following:

    • build.gradle
    • settings.gradle
    • app/
    • asset-pack-name/build.gradle
    • asset-pack-name/src/main/assets/your-asset-directories

  8. Build the Android App Bundle with Gradle. In the generated app bundle, the root-level directory now includes the following:

    • asset-pack-name/manifest/AndroidManifest.xml: Configures the asset pack’s identifier and delivery mode
    • asset-pack-name/assets/your-asset-directories: Directory that contains all assets delivered as part of the asset pack

    Gradle generates the manifest for each asset pack and outputs the assets/ directory for you.

  9. (Optional) Include the Play Asset Delivery Library if you plan to use fast-follow and on-demand delivery

    Groovy

    implementation "com.google.android.play:asset-delivery:2.0.2"
// For Kotlin use asset-delivery-ktx
implementation "com.google.android.play:asset-delivery-ktx:2.0.1"

    Kotlin

    implementation("com.google.android.play:asset-delivery:2.0.2")
// For Kotlin use core-ktx
implementation("com.google.android.play:asset-delivery-ktx:2.0.1")

  10. (Optional) Configure your app bundle to support different texture compression formats.

Integrate with the Play Asset Delivery API

The Play Asset Delivery Java API provides the AssetPackManager class for requesting asset packs, managing downloads, and accessing the assets. Make sure to Add the Play Asset Delivery Library into your project first.

You implement this API according to the delivery type of the asset pack you wish to access. These steps are shown in the following flowchart.

Asset pack flow diagram for the Java programming language

Figure 1. Flow diagram for accessing asset packs

Install-time delivery

Asset packs configured as install-time are immediately available at app launch. Use the Java AssetManager API to access assets served in this mode:

Kotlin

import android.content.res.AssetManager
...
val context: Context = createPackageContext("com.example.app", 0)
val assetManager: AssetManager = context.assets
val stream: InputStream = assetManager.open("asset-name")

Java

import android.content.res.AssetManager;
...
Context context = createPackageContext("com.example.app", 0);
AssetManager assetManager = context.getAssets();
InputStream is = assetManager.open("asset-name");

Fast-follow and on-demand delivery

The following sections show how to get information about asset packs before downloading them, how to call the API to start the download, and then how to access the downloaded packs. These sections apply to fast-follow and on-demand asset packs.

Check status

Each asset pack is stored in a separate folder in the app's internal storage. Use the getPackLocation() method to determine the root folder of an asset pack. This method returns the following values:

Return value Status
A valid AssetPackLocation object Asset pack root folder is ready for immediate access at assetsPath()
null Unknown asset pack or assets are not available

Get download information about asset packs

Apps are required to disclose the size of the download before fetching the asset pack. Use the requestPackStates() or the getPackStates() method to determine the size of the download and whether the pack is already downloading.

Kotlin

suspend fun requestPackStates(packNames: List<String>): AssetPackStates

Java

Task<AssetPackStates> getPackStates(List<String> packNames)

requestPackStates() is a suspend function returning an AssetPackStates object while the getPackStates() is an asynchronous method that returns a Task<AssetPackStates>. The packStates() method of an AssetPackStates object returns a Map<String, AssetPackState>. This map contains the state of each requested asset pack, keyed by its name:

Kotlin

AssetPackStates#packStates(): Map<String, AssetPackState>

Java

Map<String, AssetPackState> AssetPackStates#packStates()

The final request is shown by the following:

Kotlin

const val assetPackName = "assetPackName"
coroutineScope.launch {
  try {
    val assetPackStates: AssetPackStates = 
      manager.requestPackStates(listOf(assetPackName))
    val assetPackState: AssetPackState = 
      assetPackStates.packStates()[assetPackName]
  } catch (e: RuntimeExecutionException) {
    Log.d("MainActivity", e.message)
  }
}

Java

final String assetPackName = "myasset";

assetPackManager
    .getPackStates(Collections.singletonList(assetPackName))
    .addOnCompleteListener(new OnCompleteListener<AssetPackStates>() {
        @Override
        public void onComplete(Task<AssetPackStates> task) {
            AssetPackStates assetPackStates;
            try {
                assetPackStates = task.getResult();
                AssetPackState assetPackState =
                    assetPackStates.packStates().get(assetPackName);
            } catch (RuntimeExecutionException e) {
                Log.d("MainActivity", e.getMessage());
                return;
            })

The following AssetPackState methods provide the size of the asset pack, the downloaded amount so far (if requested), and the amount already transferred to the app:

To get the status of an asset pack, use the status() method, which returns the status as an integer that corresponds to a constant field in the AssetPackStatus class. An asset pack that’s not installed yet has the status AssetPackStatus.NOT_INSTALLED.

If a request fails, use the errorCode() method, whose return value corresponds to a constant field in the AssetPackErrorCode class.

Install

Use the requestFetch() or fetch() method to download an asset pack for the first time or call for the update of an asset pack to complete:

Kotlin

suspend fun AssetPackManager.requestFetch(packs: List<String>): AssetPackStates

Java

Task<AssetPackStates> fetch(List<String> packNames)

This method returns an AssetPackStates object containing a list of packs and their initial download states and sizes. If an asset pack requested via requestFetch() or fetch() is already downloading, the download status is returned and no additional download is started.

Monitor download states

You should implement an AssetPackStateUpdatedListener to track the installation progress of asset packs. The status updates are broken down per pack to support tracking the status of individual asset packs. You can start using available asset packs before all other downloads for your request have completed.

Kotlin

fun registerListener(listener: AssetPackStateUpdatedListener)
fun unregisterListener(listener: AssetPackStateUpdatedListener)

Java

void registerListener(AssetPackStateUpdatedListener listener)
void unregisterListener(AssetPackStateUpdatedListener listener)

Large downloads

If the download is larger than 150 MB and the user is not on Wi-Fi, the download does not start until the user explicitly gives their consent to proceed with the download using a mobile data connection. Similarly, if the download is large and the user loses Wi-Fi, the download is paused and explicit consent is required to proceed using a mobile data connection. A paused pack has state WAITING_FOR_WIFI. To trigger the UI flow to prompt the user for consent, use the requestCellularDataConfirmation() or showCellularDataConfirmation() method.

Note that if the app does not call this method, the download is paused and will resume automatically only when the user is back on a Wi-Fi connection.

The following is an example implementation of a listener:

Kotlin

assetPackManager.registerListener { assetPackState ->
  when(assetPackState.status()) {
    AssetPackStatus.PENDING -> {
      Log.i(TAG, "Pending")
    }
    AssetPackStatus.DOWNLOADING -> {
      val downloaded = assetPackState.bytesDownloaded()
      val totalSize = assetPackState.totalBytesToDownload()
      val percent = 100.0 * downloaded / totalSize

      Log.i(TAG, "PercentDone=" + String.format("%.2f", percent))
    }
    AssetPackStatus.TRANSFERRING -> {
      // 100% downloaded and assets are being transferred.
      // Notify user to wait until transfer is complete.
    }
    AssetPackStatus.COMPLETED -> {
      // Asset pack is ready to use. Start the game.
    }
    AssetPackStatus.FAILED -> {
      // Request failed. Notify user.
      Log.e(TAG, assetPackState.errorCode())
    }
    AssetPackStatus.CANCELED -> {
      // Request canceled. Notify user.
    }
    AssetPackStatus.WAITING_FOR_WIFI -> {
      if (!waitForWifiConfirmationShown) {
        coroutineScope.launch {
          val resultCode =
            assetPackManager.requestCellularDataConfirmation(this@MainActivity)
          if (resultCode == RESULT_OK) {
            Log.d(TAG, "Confirmation dialog has been accepted.")
          } else if (resultCode == RESULT_CANCELED) {
            Log.d(TAG, "Confirmation dialog has been denied by the user.")
          }
        }
        waitForWifiConfirmationShown = true
      }
    }
    AssetPackStatus.NOT_INSTALLED -> {
      // Asset pack is not downloaded yet.
    }
    AssetPackStatus.UNKNOWN -> {
      Log.wtf(TAG, "Asset pack status unknown")
    }
  }
}

Java

assetPackStateUpdateListener = new AssetPackStateUpdateListener() {
    @Override
    public void onStateUpdate(AssetPackState assetPackState) {
      switch (assetPackState.status()) {
        case AssetPackStatus.PENDING:
          Log.i(TAG, "Pending");
          break;

        case AssetPackStatus.DOWNLOADING:
          long downloaded = assetPackState.bytesDownloaded();
          long totalSize = assetPackState.totalBytesToDownload();
          double percent = 100.0 * downloaded / totalSize;

          Log.i(TAG, "PercentDone=" + String.format("%.2f", percent));
          break;

        case AssetPackStatus.TRANSFERRING:
          // 100% downloaded and assets are being transferred.
          // Notify user to wait until transfer is complete.
          break;

        case AssetPackStatus.COMPLETED:
          // Asset pack is ready to use. Start the game.
          break;

        case AssetPackStatus.FAILED:
          // Request failed. Notify user.
          Log.e(TAG, assetPackState.errorCode());
          break;

        case AssetPackStatus.CANCELED:
          // Request canceled. Notify user.
          break;

        case AssetPackStatus.WAITING_FOR_WIFI:
          if (!waitForWifiConfirmationShown) {
            assetPackManager.showCellularDataConfirmation(MainActivity.this)
              .addOnSuccessListener(new OnSuccessListener<Integer> () {
                @Override
                public void onSuccess(Integer resultCode) {
                  if (resultCode == RESULT_OK) {
                    Log.d(TAG, "Confirmation dialog has been accepted.");
                  } else if (resultCode == RESULT_CANCELED) {
                    Log.d(TAG, "Confirmation dialog has been denied by the user.");
                  }
                }
              });
            waitForWifiConfirmationShown = true;
          }
          break;

        case AssetPackStatus.NOT_INSTALLED:
          // Asset pack is not downloaded yet.
          break;
        case AssetPackStatus.UNKNOWN:
          Log.wtf(TAG, "Asset pack status unknown")
          break;
      }
    }
}

Alternatively, you can use the getPackStates() method to get the status of current downloads. AssetPackStates contains the download progress, download status, and any failure error codes.

Access asset packs

You can access an asset pack using file system calls after the download request reaches the COMPLETED state. Use the getPackLocation() method to get the root folder of the asset pack.

Assets are stored in the assets directory within the asset pack root directory. You can get the path to the assets directory by using the convenience method assetsPath(). Use the following method to get the path to a specific asset:

Kotlin

private fun getAbsoluteAssetPath(assetPack: String, relativeAssetPath: String): String? {
    val assetPackPath: AssetPackLocation =
      assetPackManager.getPackLocation(assetPack)
      // asset pack is not ready
      ?: return null

    val assetsFolderPath = assetPackPath.assetsPath()
    // equivalent to: FilenameUtils.concat(assetPackPath.path(), "assets")
    return FilenameUtils.concat(assetsFolderPath, relativeAssetPath)
}

Java

private String getAbsoluteAssetPath(String assetPack, String relativeAssetPath) {
    AssetPackLocation assetPackPath = assetPackManager.getPackLocation(assetPack);

    if (assetPackPath == null) {
        // asset pack is not ready
        return null;
    }

    String assetsFolderPath = assetPackPath.assetsPath();
    // equivalent to: FilenameUtils.concat(assetPackPath.path(), "assets");
    String assetPath = FilenameUtils.concat(assetsFolderPath, relativeAssetPath);
    return assetPath;
}

Other Play Asset Delivery API methods

The following are some additional API methods you may want to use in your app.

Cancel request

Use cancel() to cancel an active asset pack request. Note that this request is a best-effort operation.

Remove an asset pack

Use requestRemovePack() or removePack() to schedule the removal of an asset pack.

Get locations of multiple asset packs

Use getPackLocations() to query the status of multiple asset packs in bulk, which returns a map of asset packs and their locations. The map returned by getPackLocations() contains an entry for each pack that is currently downloaded and up-to-date.

Next step

Test Play Asset Delivery locally and from Google Play.