46 lines
4.2 KiB
Markdown
46 lines
4.2 KiB
Markdown
---
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uid: addressables-api-download-dependencies-async
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---
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# Preload dependencies
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When you distribute content remotely, you can improve performance by downloading dependencies in advance of when your application needs them. For example, you can download essential content on start up when your game is launched for the first time to make sure that users don't have to wait for content in the middle of gameplay.
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## Download dependencies
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Use the [`Addressables.DownloadDependenciesAsync`](xref:UnityEngine.AddressableAssets.Addressables.DownloadDependenciesAsync*) method to make sure that all the dependencies needed to load an Addressable key are available either in local content installed with the app or the download cache:
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[!code-cs[sample](../Tests/Editor/DocExampleCode/MiscellaneousTopics.cs#doc_Download)]
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> [!TIP]
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> If you have a set of assets that you want to pre-download, you can assign the same label, such as `preload`, to the assets and use that label as the key when calling [`Addressables.DownloadDependenciesAsync`](xref:UnityEngine.AddressableAssets.Addressables.DownloadDependenciesAsync*). Addressables downloads all the AssetBundles containing an asset with that label if not already available, along with any bundles containing the assets' dependencies.
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## Get progress updates
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An [`AsyncOperationHandle`](xref:UnityEngine.ResourceManagement.AsyncOperations.AsyncOperationHandle) instance provides the following ways to get progress updates:
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* [`AsyncOperationHandle.PercentComplete`](xref:UnityEngine.ResourceManagement.AsyncOperations.AsyncOperationHandle.PercentComplete): Reports the percentage of sub-operations that have finished. For example, if an operation uses six sub-operations to perform its task, the `PercentComplete` indicates the entire operation is 50% complete when three of those operations have finished (it doesn't matter how much data each operation loads).
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* [`AsyncOperationHandle.GetDownloadStatus`](xref:UnityEngine.ResourceManagement.AsyncOperations.AsyncOperationHandle.GetDownloadStatus): Returns a [`DownloadStatus`](xref:UnityEngine.ResourceManagement.AsyncOperations.DownloadStatus) struct that reports the percentage in terms of total download size. For example, if an operation has six sub-operations, but the first operation represented 50% of the total download size, then `GetDownloadStatus` indicates the operation is 50% complete when the first operation finishes.
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The following example illustrates how you can use `GetDownloadStatus` to check the status and dispatch progress events during the download:
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[!code-cs[sample](../Tests/Editor/DocExampleCode/PreloadWithProgress.cs#doc_Preload)]
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To discover how much data you need to download to load one or more assets, you can call [`Addressables.GetDownloadSizeAsync`](xref:UnityEngine.AddressableAssets.Addressables.GetDownloadSizeAsync*):
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[!code-cs[sample](../Tests/Editor/DocExampleCode/PreloadWithProgress.cs#doc_DownloadSize)]
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The `Result` of the completed operation is the number of bytes that must be downloaded. If Addressables has already cached all the required AssetBundles, then `Result` is zero.
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Always release the download operation handle after you have read the `Result` object. If you don't need to access the results of the download operation, you can automatically release the handle by setting the `autoReleaseHandle` parameter to true, as shown in the following example:
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[!code-cs[sample](../Tests/Editor/DocExampleCode/Preload.cs#doc_Preload)]
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### Clear the dependency cache
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If you want to clear any AssetBundles cached by Addressables, call [`Addressables.ClearDependencyCacheAsync`](xref:UnityEngine.AddressableAssets.Addressables.ClearDependencyCacheAsync*). This method clears the cached AssetBundles containing the assets identified by a key along with any bundles containing those assets' dependencies.
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`ClearDependencyCacheAsync` only clears assets bundles related to the specified key. If you updated the content catalog so the key no longer exists or it no longer depends on the same AssetBundles, then these bundles remain in the cache until they expire based on [cache settings](xref:UnityEngine.Cache).
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To clear all AssetBundles, you can use the methods in the [UnityEngine.Caching](xref:UnityEngine.Caching) class.
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