集成 Asset Delivery (Unity)

在集成 Asset Delivery 时,Unity 游戏 可以使用 Addressables 或 AssetBundle 访问资源包。Addressables 是最近推出且推荐使用的 Asset Delivery 解决方案,适用于使用 Unity 2019.4 或更高版本构建的游戏;AssetBundle 则支持 Unity 2017.4 和 2018.4 中的资源包。

Unity Addressables

使用 Unity 2019.4 或更高版本构建的游戏应将 Addressables 用于 Android 设备上的 Asset Delivery。Unity 会提供 Play Asset Delivery (PAD) API,以便使用 Addressables 来处理 Android 资源包。如需了解如何使用 Addressables,请参阅以下资源:

使用 AssetBundle 文件

使用 Unity 2017.4 和 2018.4 构建的游戏可以将 AssetBundle 文件用于 asset 分发应用Unity AssetBundle 文件包含可在应用运行时由 Unity 引擎加载的序列化资源。这些文件是平台专用的(例如,针对 Android 构建),并且可与资源包结合使用。最常见的情况是,将一个 AssetBundle 文件打包成单个资源包,并且资源包与 AssetBundle 使用相同的名称。如果您希望更灵活地创建资源包,请使用 API 配置资源包。

在运行时,可使用 Play Asset Delivery for Unity 类来检索打包在资源包中的 AssetBundle。

前提条件

  1. 适用于 Unity 的 Google 软件包中下载最新版本的 Play Asset Delivery Unity 插件。

  2. 在 Unity 中创建 AssetBundle

使用界面配置 AssetBundle

  1. 配置资源包中的每个 AssetBundle:

    1. 依次选择 Google > Android App Bundle > Asset Delivery Settings
    2. 如需选择直接包含 AssetBundle 文件的文件夹,请点击 Add Folder

  2. 针对每个 Bundle,将 Delivery Mode 更改为 Install TimeFast FollowOn Demand。解决所有错误或依赖项,然后关闭窗口。

  3. 依次选择 Google > Build Android App Bundle 以构建 App Bundle。

  4. (可选)配置 App Bundle 以支持不同的纹理压缩格式

使用 API 配置资源包

您可以通过能作为自动化构建系统的一部分运行的编辑器脚本配置 Asset Delivery。

使用 AssetPackConfig 类定义需要包含在 Android App Bundle build 中的资源,以及这些资源的分发模式。这些资源包无需包含 AssetBundle。

public void ConfigureAssetPacks {
   // Creates an AssetPackConfig with a single asset pack, named
   // examplePackName, containing all the files in path/to/exampleFolder.
   var assetPackConfig = new AssetPackConfig();
   assetPackConfig.AddAssetsFolder("examplePackName",
                                   "path/to/exampleFolder",
                                   AssetPackDeliveryMode.OnDemand);

   // Configures the build system to use the newly created assetPackConfig when
   // calling Google > Build and Run or Google > Build Android App Bundle.
   AssetPackConfigSerializer.SaveConfig(assetPackConfig);

   // Alternatively, use BundleTool.BuildBundle to build an App Bundle from script.
   BuildBundle(new buildPlayerOptions(), assetPackConfig);
}

在给定 BuildPlayerOptionsAssetPackConfig 的情况下,您还可以在 Bundletool 类中使用静态 BuildBundle 方法生成具有资源包的 Android App Bundle。

如需指导教程,请参阅“在 Unity 游戏中使用 Play Asset Delivery”Codelab

与 Play Asset Delivery Unity API 集成

Play Asset Delivery Unity API 提供了用于请求资源包、管理下载内容和获取资源的功能。请务必先将 Unity 插件添加到您的项目中。

您在该 API 中使用的函数取决于您创建资源包的方式。

如果您使用插件界面创建资源包,请选择插件配置的资源包

如果您使用 API(或插件界面)创建资源包,请选择 API 配置的资源包

根据您希望获取的资源包的分发类型实现该 API。这些步骤如以下流程图所示。

针对插件的资源包流程图

图 1. 获取资源包流程图

检索 AssetBundle

导入 Play Asset Delivery 库,然后调用 RetrieveAssetBundleAsync() 方法检索 AssetBundle。

using Google.Play.AssetDelivery;

// Loads the AssetBundle from disk, downloading the asset pack containing it if necessary.
PlayAssetBundleRequest bundleRequest = PlayAssetDelivery.RetrieveAssetBundleAsync(asset-bundle-name);

安装时分发

配置为 install-time 的资源包可以在应用启动后立即使用。您可以使用以下代码加载 AssetBundle 中的场景:

AssetBundle assetBundle = bundleRequest.AssetBundle;

// You may choose to load scenes from the AssetBundle. For example:
string[] scenePaths = assetBundle.GetAllScenePaths();
SceneManager.LoadScene(scenePaths[path-index]);

快速跟进式分发和按需分发

以下几部分适用于 fast-followon-demand 资源包。

查看状态

每个资源包都存储于应用的内部存储空间内单独的文件夹中。使用 isDownloaded() 方法确定资源包是否已下载。

监控下载

查询 PlayAssetBundleRequest 对象以监控请求的状态:

// Download progress of request, between 0.0f and 1.0f. The value will always be
// 1.0 for assets delivered as install-time.
// NOTE: A value of 1.0 will only signify the download is complete. It will still need to be loaded.
float progress = bundleRequest.DownloadProgress;

// Returns true if:
//   * it had either completed the download, installing, and loading of the AssetBundle,
//   * OR if it has encountered an error.
bool done = bundleRequest.IsDone;

// Returns status of retrieval request.
AssetDeliveryStatus status = bundleRequest.Status;
switch(status) {
    case AssetDeliveryStatus.Pending:
        // Asset pack download is pending - N/A for install-time assets.
    case AssetDeliveryStatus.Retrieving:
        // Asset pack is being downloaded and transferred to app storage.
        // N/A for install-time assets.
    case AssetDeliveryStatus.Available:
        // Asset pack is downloaded on disk but NOT loaded into memory.
        // For PlayAssetPackRequest(), this indicates that the request is complete.
    case AssetDeliveryStatus.Loading:
        // Asset pack is being loaded.
    case AssetDeliveryStatus.Loaded:
        // Asset pack has finished loading, assets can now be loaded.
        // For PlayAssetBundleRequest(), this indicates that the request is complete.
    case AssetDeliveryStatus.Failed:
        // Asset pack retrieval has failed.
    case AssetDeliveryStatus.WaitingForWifi:
        // Asset pack retrieval paused until either the device connects via Wi-Fi,
        // or the user accepts the PlayAssetDelivery.ShowConfirmationDialog dialog.
    case AssetDeliveryStatus.RequiresUserConfirmation:
        // Asset pack retrieval paused until the user accepts the
        // PlayAssetDelivery.ShowConfirmationDialog dialog.
    default:
        break;
}

下载内容较大

大于 200MB 的资源包可以自动下载,但只能通过 Wi-Fi 下载。如果用户未连接到 WLAN,PlayAssetBundleRequest 状态会设置为 AssetDeliveryStatus.WaitingForWifi,下载也会暂停。在这种情况下,要么等到设备连接到 WLAN 再恢复下载,要么提示用户批准通过移动网络连接下载资源包。

需要用户确认

如果某个资源包的状态为 AssetDeliveryStatus.RequiresUserConfirmation, 在用户接受使用 PlayAssetDelivery.ShowConfirmationDialog()。如果应用 。请注意,调用 在这种情况下,PlayAssetDelivery.ShowConfirmationDialog() 会导致应用 。更新后,再次请求资源。

if(request.Status == AssetDeliveryStatus.RequiresUserConfirmation
   || request.Status == AssetDeliveryStatus.WaitingForWifi) {
    var userConfirmationOperation = PlayAssetDelivery.ShowConfirmationDialog();
    yield return userConfirmationOperation;

    switch(userConfirmationOperation.GetResult()) {
        case ConfirmationDialogResult.Unknown:
            // userConfirmationOperation finished with an error. Something went
            // wrong when displaying the prompt to the user, and they weren't
            // able to interact with the dialog.
        case ConfirmationDialogResult.Accepted:
            // User accepted the confirmation dialog--an update will start.
        case ConfirmationDialogResult.Declined:
            // User canceled or declined the dialog. It can be shown again.
        default:
            break;
    }
}

取消请求(仅限按需)

如果您在 AssetBundle 加载到内存中之前需要取消请求,请对 PlayAssetBundleRequest 对象调用 AttemptCancel() 方法:

// Will only attempt if the status is Pending, Retrieving, or Available - otherwise
// it will be a no-op.
bundleRequest.AttemptCancel();

// Check to see if the request was successful by checking if the error code is Canceled.
if(bundleRequest.Error == AssetDeliveryErrorCode.Canceled) {
    // Request was successfully canceled.
}

异步请求资源包

在大多数情况下,您应使用协程异步请求资源包并监控进度,如下所示:

private IEnumerator LoadAssetBundleCoroutine(string assetBundleName) {

    PlayAssetBundleRequest bundleRequest =
        PlayAssetDelivery.RetrieveAssetBundleAsync(assetBundleName);

    while (!bundleRequest.IsDone) {
        if(bundleRequest.Status == AssetDeliveryStatus.WaitingForWifi) {
            var userConfirmationOperation = PlayAssetDelivery.ShowCellularDataConfirmation();

            // Wait for confirmation dialog action.
            yield return userConfirmationOperation;

            if((userConfirmationOperation.Error != AssetDeliveryErrorCode.NoError) ||
               (userConfirmationOperation.GetResult() != ConfirmationDialogResult.Accepted)) {
                // The user did not accept the confirmation. Handle as needed.
            }

            // Wait for Wi-Fi connection OR confirmation dialog acceptance before moving on.
            yield return new WaitUntil(() => bundleRequest.Status != AssetDeliveryStatus.WaitingForWifi);
        }

        // Use bundleRequest.DownloadProgress to track download progress.
        // Use bundleRequest.Status to track the status of request.

        yield return null;
    }

    if (bundleRequest.Error != AssetDeliveryErrorCode.NoError) {
        // There was an error retrieving the bundle. For error codes NetworkError
        // and InsufficientStorage, you may prompt the user to check their
        // connection settings or check their storage space, respectively, then
        // try again.
        yield return null;
    }

    // Request was successful. Retrieve AssetBundle from request.AssetBundle.
    AssetBundle assetBundle = bundleRequest.AssetBundle;

如需详细了解如何处理错误,请参阅 AssetDeliveryErrorCodes 列表。

其他 Play Core API 方法

以下是您可能希望在应用中使用的一些其他 API 方法。

检查下载内容大小

向 Google Play 发出异步调用并针对操作何时完成设置回调方法,从而检查 AssetBundle 的大小:

public IEnumerator GetDownloadSize() {
   PlayAsyncOperation<long> getSizeOperation =
   PlayAssetDelivery.GetDownloadSize(assetPackName);

   yield return getSizeOperation;
   if(operation.Error != AssetDeliveryErrorCode.NoError) {
       // Error while retrieving download size.
    } else {
        // Download size is given in bytes.
        long downloadSize = operation.GetResult();
    }
}

移除 AssetBundle

您可以移除当前未加载到内存中的快速跟进式分发和按需分发 AssetBundle。发出以下异步调用,并针对何时完成设置回调方法:

PlayAsyncOperation<string> removeOperation = PlayAssetDelivery.RemoveAssetPack(assetBundleName);

removeOperation.Completed += (operation) =>
            {
                if(operation.Error != AssetDeliveryErrorCode.NoError) {
                    // Error while attempting to remove AssetBundles.
                } else {
                    // Files were deleted OR files did not exist to begin with.
                }
            };

后续步骤

在本地和通过 Google Play 测试 Asset Delivery 情况