Unity provides APIs to manage asset packs at runtime. They use Google’s PlayCore API, which means they have the same limitations as PlayCore, and can’t manage install-time asset packs. Using the PlayCore API also means your application requires the PlayCore plugin. If your project has asset packs, either custom asset packs or Unity-generated asset packs, Unity automatically adds the PlayCore dependency to the application’s manifest.
アセットパックをダウンロードし、そのアセットにアクセスする方法は、アセットパックの配信モードによって異なります。アセットパックの配信モードは 3 種類あります。
install-time: Google Play automatically downloads install-time asset packs when the device installs the application. Google Play considers these asset packs to be part of the base application, and an end user can’t uninstall them without uninstalling the entire application. The PlayCore API doesn’t handle install-time asset packs, which means that you can’t check the status, request to download, or remove install-time asset packs. You also can’t directly access assets inside of these asset packs, except streaming assets in Unity-generated install-time asset packs. To access streaming assets, use Application.streamingAssetsPath to get the path to streaming assets location, then use UnityWebRequest to access assets in that path. If you create a custom asset pack, you can’t access assets inside it using standard file APIs. Instead, use Android’s AssetManager APIs.fast-follow: Google Play automatically starts to download fast-follow asset packs after it installs the application. However, it is possible that not all fast-follow asset packs are available on the first time the application launches. To check the status and download fast-follow asset packs, see Download asset packs.on-demand: Google Play doesn’t automatically download on-demand asset packs. You have to manually start the download. For information on how to do this, see below.配信モードの詳細については、配信モード を参照してください。
If your application uses fast-follow or on-demand asset packs, the device must download these asset packs before the application can access assets inside of them. To check the status of asset packs and download them if they are not on the device, you must first know the name of each asset pack. To get the names of Unity-generated asset packs, call AndroidAssetPacks.GetCoreUnityAssetPackNames. There is no runtime API to get the names of custom asset packs so you must keep track of them yourself. You set the name of custom asset packs at build time; it’s the name of the directory.
アセットパックの名前がわかったら、各アセットパックの状態を確認するために、AndroidAssetPacks.GetAssetPackStateAsync にアセットパックの名前を渡して呼び出します。これにより、問い合わせたアセットパックの状態が返されるので、その結果をもとに、アセットパックをダウンロードする必要があるかどうかを判断することができます。Unity が生成したすべてのアセットパックの状態をすばやく照会したい場合は、AndroidAssetPacks.coareUnityAssetPacksDownloaded を使用します。これは、最初のシーン以外をロードしたり、Unity が扱う他のリソースにアクセスしようとする前に、Unity が生成したすべてのアセットパックが利用可能であることを確認できるため便利です。
For every asset pack you need to download, call AndroidAssetPacks.DownloadAssetPackAsync, passing in the asset pack name. While the asset pack downloads, monitor the download status because downloads can pause or fail. There are two ways to do this: