Many tasks in the Addressables need to load or download information before they can return a result. To avoid blocking program execution, Addressables implements such tasks as asynchronous operations.

譯：Addressables中有許多任務需要在返回結(jié)果之前加載或下載信息。為了避免阻塞程序執(zhí)行，Addressables將這些任務實現(xiàn)為異步操作

In contrast to a synchronous operation, which doesn’t return control until the result is available, an asynchronous operation returns control to the calling function almost immediately. However, the results may not be available until some time in the future. When you call a function, such as?LoadAssetAsync, it doesn't return the loaded assets directly. Instead, it returns an?AsyncOperationHandle?object, which you can use to access the loaded assets when they become available.

譯：與同步操作不同的是，異步操作幾乎立即將控制權(quán)返回給調(diào)用函數(shù)，但是結(jié)果可能要在未來的某個時間才能獲得。當調(diào)用函數(shù)（例如LoadAssetAsync）時，它不會直接返回加載的資產(chǎn)，而是返回一個AsyncOperationHandle對象，當資產(chǎn)可用時，

You can use the following techniques to wait for the results of an asynchronous operation (while allowing other scripts to continue processing).

譯：您可以使用該對象訪問它們。您可以使用以下技術(shù)等待異步操作的結(jié)果（同時允許其他腳本繼續(xù)處理）

• Coroutines and IEnumerator loops??協(xié)程和IEnumerator循環(huán)

• Events? ??事件

• Tasks? ? ??任務

NOTE

You can block the current thread to wait for the completion of an asynchronous operation. Doing so can introduce performance problems and frame rate hitches. See?Using operations synchronously.

譯：你可以阻塞當前線程以等待異步操作的完成。這樣做可能會引入性能問題和幀速率卡頓。請參閱使用同步操作

Releasing AsyncOperationHandle instances

Methods, like?LoadAssetsAsync, return?AsyncOperationHandle?instances that both provide the results of the operation and a way to release both the results and the operation object itself. You must retain the handle object for as long as you want to use the results. Depending on the situation, that might be one frame, until the end of a level, or even the lifetime of the application. Use the?Addressables.Release?function to release operation handles and any associated addressable assets.

譯：像 LoadAssetsAsync 這樣的方法返回 AsyncOperationHandle 實例，它們提供操作的結(jié)果以及釋放結(jié)果和操作對象本身的方式。只要你想使用結(jié)果，就必須保留處理對象。根據(jù)情況，可能是一幀、直到關卡結(jié)束，甚至是應用程序的生命周期。使用 Addressables.Release 函數(shù)釋放操作句柄和任何相關的可尋址資源。

Releasing an operation handle decrements the reference count of any assets loaded by the operation and invalidates the operation handle object itself. See?Memory management?for more information about reference counting in the Addressables system.

譯：釋放操作句柄會減少操作加載的任何資源的引用計數(shù)，并使操作句柄對象本身無效。有關 Addressables 系統(tǒng)中引用計數(shù)的更多信息，請參閱內(nèi)存管理。

In cases where you don’t need to use the results of an operation beyond a limited scope, you can release the handles right away. A few Addressables methods, such as?UnloadSceneAsync?allow you to automatically release the operation handle when it's complete.

譯：在某些情況下，如果不需要在受限范圍之外使用操作結(jié)果，可以立即釋放句柄。一些 Addressables 方法，例如 UnloadSceneAsync，允許你在完成時自動釋放操作句柄。如果操作失敗，你仍然應該釋放操作句柄。

If an operation is unsuccessful, you should still release the operation handle. Normally, Addressables releases any assets that it loaded during a failed operation, but releasing the handle still clears the handle’s instance data. Note that some functions, like?LoadAssetsAsync, which load multiple assets, give you the option to either retain any assets that it could load or to fail and release everything if any part of the load operation failed.

譯：在某些情況下，如果不需要在受限范圍之外使用操作結(jié)果，可以立即釋放句柄。一些 Addressables 方法，例如 UnloadSceneAsync，允許你在完成時自動釋放操作句柄。如果操作失敗，你仍然應該釋放操作句柄。通常，Addressables 在操作失敗時會釋放它加載的任何資源，但釋放句柄仍會清除句柄的實例數(shù)據(jù)。請注意，一些函數(shù)（如 LoadAssetsAsync）允許你選擇保留它可以加載的任何資源或在加載操作的任何部分失敗時失敗并釋放所有內(nèi)容。基于協(xié)程和 IEnumerator 的操作處理。AsyncOperationHandle 實現(xiàn) IEnumerator 接口，并將繼續(xù)迭代，直到操作完成。

Coroutine- and IEnumerator-based operation handling

The?AsyncOperationHandle?implements the?IEnumerator?interface and will continue iteration until the operation is complete. In a coroutine, you can yield the operation handle to wait for the next iteration. When complete, the execution flow continues to the following statements. Recall that you can implement the?MonoBehaviour Start?function as a coroutine, which is a good way to have a GameObject load and instantiate the assets it needs.

譯：在協(xié)程中，你可以使用 yield 關鍵字來等待操作處理，等待結(jié)束后，執(zhí)行流程繼續(xù)執(zhí)行以下語句。請記住，你可以將 MonoBehaviour 的 Start 函數(shù)實現(xiàn)為協(xié)程，這是一個很好的方式，可以讓 GameObject 加載并實例化它所需的資產(chǎn)。

The following script loads a Prefab as a child of its GameObject using a Start function coroutine. It yields the AsyncOperationHandle until the operation finishes and then uses the same handle to instantiate the Prefab.

譯：下面的腳本使用 Start 函數(shù)協(xié)程將 Prefab 作為其 GameObject 的子對象進行加載，并在操作完成后使用相同的句柄來實例化 Prefab

Note that?Addressables.LoadAssetsAsync?is not able to be canceled once started. However, releasing the handle before it has finished will decrement the handle reference count and it will automatically release when the load is complete.

譯：請注意，Addressables.LoadAssetsAsync一旦啟動就無法取消。但是，在它完成之前釋放句柄會遞減句柄引用計數(shù)，并在加載完成時自動釋放

See?Coroutines?for more information.

譯：有關詳細信息，請參閱協(xié)程

Grouping operations in a coroutine

You will probably encounter situations in which you want to perform several operations before moving on to the next step in your game logic. For example, you want to load a number of Prefabs and other assets before you start a level.

譯：您可能會遇到這樣的情況，在進行游戲邏輯的下一步之前，您希望執(zhí)行多個操作。例如，您希望在開始關卡之前加載多個Prefab和其他資產(chǎn)

If the operations all load assets, you can combine them with a single call to the?Addressables.LoadAssetsAsync?function. The AsyncOperationhandle for this method works the same as?LoadAssetAsync; you can yield the handle in a coroutine to wait until all the assets in the operation load. In addition, you can pass a callback function to LoadAssetsAsync and the operation calls that function when it finishes loading a specific asset. See?Loading multiple assets?for an example.

譯：如果這些操作都是加載資產(chǎn)，您可以使用單個調(diào)用Addressables.LoadAssetsAsync函數(shù)將它們組合在一起。該方法的AsyncOperationhandle與LoadAssetAsync相同；您可以在協(xié)程中yield該句柄，以等待操作中所有資產(chǎn)的加載。此外，您可以將回調(diào)函數(shù)傳遞給LoadAssetsAsync，當操作完成加載特定資產(chǎn)時，操作會調(diào)用該函數(shù)。請參閱加載多個資產(chǎn)以獲得示例

Another option is to use the?ResourceManager.CreateGenericGroupOperation?to create a group operation that completes when all of its members finish.

譯：另一個選項是使用ResourceManager.CreateGenericGroupOperation創(chuàng)建一個組操作，當其所有成員完成時，該操作將完成

Event-based operation handling

You can add a delegate function to the?Completed?event of an?AsyncOperationHandle. The operation calls the delegate function when it's finished.

譯：您可以將委托函數(shù)添加到AsyncOperationHandle的Completed事件中。當操作完成時，操作會調(diào)用委托函數(shù)

The following script performs the same function as the example in?Coroutine- and IEnumerator-based operation handling, but uses an event delegate instead of a coroutine.

譯：以下腳本執(zhí)行與Coroutine- and IEnumerator-based操作處理示例相同的功能，但使用事件委托而不是協(xié)程

Note that the handle instance passed to the event delegate is the same as that returned by the original function call. You can use either to access the results and status of the operation and, ultimately, to release the operation handle and loaded assets.

譯：傳遞給事件委托的句柄實例與原始函數(shù)調(diào)用返回的句柄相同。你可以使用任一句柄來訪問操作的結(jié)果和狀態(tài)，最終釋放操作句柄和已加載的資產(chǎn)

Task-based operation handling

The?AsyncOperationHandle?provides a?Task?object that you can use with the C#?async?and?await?keywords to sequence code that calls asynchronous functions and handles the results.

譯：使用基于任務的操作處理時，AsyncOperationHandle 提供了一個 Task 對象，你可以在調(diào)用異步函數(shù)并處理結(jié)果的代碼中使用 C# 的 async 和 await 關鍵字來進行序列化

The following example loads Addressable assets using a list of keys. The differences between this task-based approach and the coroutine or event-based approaches are in the signature of the calling function, which must include the?async?keyword and the use of the?await?keyword with the operation handle’s Task property. The calling function, Start() in this case, suspends operation while the task finishes. Execution then resumes and the example instantiates all the loaded Prefabs (in a grid pattern).

譯：下面的示例使用鍵列表加載 Addressable 資產(chǎn)。這種基于任務的方法與協(xié)程或事件驅(qū)動方法的區(qū)別在于調(diào)用函數(shù)的簽名，必須包括 async 關鍵字，并使用 await 關鍵字與操作句柄的 Task 屬性。在這種情況下，調(diào)用函數(shù) Start() 暫停操作，直到任務完成。然后，示例根據(jù)網(wǎng)格模式實例化所有已加載的 Prefab

IMPORTANT

The?AsyncOperationHandle.Task?property is not available on the Unity WebGL platform, which doesn't support multitasking.

譯：Unity WebGL 平臺不支持多任務，因此 AsyncOperationHandle.Task 屬性在該平臺上不可用

When you use Task-based operation handling, you can use the C#?Task?class methods such as?WhenAll?to control which operations you run in parallel and which you want to run in sequence. The following example illustrates how to wait for more than one operation to finish before moving onto the next task:

譯：當你使用基于任務的操作處理時，可以使用 C# 的 Task 類方法（例如 WhenAll）來控制并行運行的操作和需要按順序運行的操作。以下示例說明了如何在移動到下一個任務之前等待多個操作完成

Using operations synchronously

You can wait for an operation to finish without yielding, waiting for an event, or using?async await?by calling an operation’s?WaitForCompletion?method. This method blocks the current program execution thread while it waits for the operation to finish before continuing in the current scope.

譯：通過調(diào)用操作的 WaitForCompletion 方法，您可以在不使用 yield、等待事件或使用 async await 的情況下等待操作完成。該方法會阻塞當前程序執(zhí)行線程，直到操作完成后才在當前作用域中繼續(xù)執(zhí)行

Avoid calling WaitForCompletion on operations that can take a significant amount of time, such as those that must download data. Calling WaitForCompletion can cause frame hitches and interrupt UI responsiveness.

譯：避免在需要下載數(shù)據(jù)的操作上調(diào)用 WaitForCompletion，因為這會導致幀停頓并中斷 UI 的響應

In Unity 2020.1 or earlier, Unity also waits for all other pending asynchronous operations to finish, so the delay in execution can be much longer than that required for just the single operation for which you call this method. In Unity 2020.2 or later, the performance impact can be less pronounced, at least when loading assets that have already been downloaded.

譯：在 Unity 2020.1 或更早版本中，Unity 還會等待所有其他待處理的異步操作完成，因此執(zhí)行的延遲可能比您調(diào)用此方法的單個操作所需的時間長得多。在 Unity 2020.2 或更高版本中，性能影響可能會較小，至少在加載已經(jīng)下載的資源時如此

The following example loads a Prefab asset by address, waits for the operation to complete, and then instantiates the Prefab:

譯：以下示例通過地址加載 Prefab 資源，等待操作完成，然后實例化 Prefab：

Custom operations

To create a custom operation, extend the?AsyncOperationBase?class and override its virtual methods.

譯：要創(chuàng)建自定義操作，請擴展 AsyncOperationBase 類并重寫其虛擬方法

You can pass the derived operation to the?ResourceManager.StartOperation?method to start the operation and receive an?AsyncOperationHandle?struct. The?ResourceManager?registers operations started this way and shows them in the Addressables?Event Viewer.

譯：您可以將派生操作傳遞給 ResourceManager.StartOperation 方法以啟動操作并接收 AsyncOperationHandle 結(jié)構(gòu)。ResourceManager 會注冊以這種方式啟動的操作并在 Addressables 事件查看器中顯示它們

Executing the operation

The?ResourceManager?invokes the?AsyncOperationBase.Execute?method for your custom operation once the optional dependent operation completes.

譯：ResourceManager 在可選的依賴操作完成后為您的自定義操作調(diào)用 AsyncOperationBase.Execute 方法

Completion handling

When your custom operation completes, call?AsyncOperationBase.Complete?on your custom operation object. You can call this within the?Execute?method or defer it to outside the call.

譯：當您的自定義操作完成時，請在自定義操作對象上調(diào)用 AsyncOperationBase.Complete。您可以在 Execute 方法內(nèi)部調(diào)用它，也可以將其推遲到調(diào)用外部

AsyncOperationBase.Complete notifies the?ResourceManager?that the operation has finished. The ResourceManager invokes the associated?AsyncOperationHandle.Completed?events for the relevant instances of the custom operation.

譯：AsyncOperationBase.Complete 通知 ResourceManager 操作已完成。ResourceManager 為相關自定義操作的 AsyncOperationHandle.Completed 事件調(diào)用相應的實例

Terminating the operation

The?ResourceManager?invokes the?AsyncOperationBase.Destroy?method for your custom operation when the operation?AsyncOperationBase.ReferenceCount?reaches zero.

譯：當操作 AsyncOperationBase.ReferenceCount 達到零時，ResourceManager 會為您的自定義操作調(diào)用 AsyncOperationBase.Destroy 方法

The?AsyncOperationBase.ReferenceCount?is decreased when the?AsyncOperationHandle?that references it is released using?Addressables.Release?or when?AsyncOperationBase.DecrementReferenceCount?is called by a custom operation internally.?AsyncOperationBase.Destroy?is where you should release any memory or resources associated with your custom operation.

譯：當釋放引用它的 AsyncOperationHandle 或自定義操作內(nèi)部調(diào)用 AsyncOperationBase.DecrementReferenceCount 時，AsyncOperationBase.ReferenceCount 會減少。AsyncOperationBase.Destroy 是您釋放與自定義操作關聯(lián)的任何內(nèi)存或資源的位置

Using typed versus typeless operation handles

Most?Addressables?methods that start an operation return a generic?AsyncOperationHandle<T>?struct, allowing type safety for the?AsyncOperationHandle.Completed?event and for the?AsyncOperationHandle.Result?object. You can also use a non-generic?AsyncOperationHandle?struct and convert between the two handle types as desired.

譯：大多數(shù) Addressables 啟動操作的方法都返回通用的 AsyncOperationHandle 結(jié)構(gòu)，允許為 AsyncOperationHandle.Completed 事件和 AsyncOperationHandle.Result 對象提供類型安全。您還可以使用非泛型的 AsyncOperationHandle 結(jié)構(gòu)并根據(jù)需要在兩種句柄類型之間進行轉(zhuǎn)換

Note that a runtime exception occurs if you attempt to cast a non-generic handle to a generic handle of an incorrect type. For example:

譯：如果您嘗試將非泛型句柄轉(zhuǎn)換為不正確類型的泛型句柄，將會引發(fā)運行時異常。例如

Reporting operation progress

AsyncOperationHandle?has two methods that you can use to monitor and report the progress of the operation:

譯：異步操作句柄（AsyncOperationHandle）有兩種方法可以用來監(jiān)視和報告操作的進度

• GetDownloadStatus?returns a?DownloadStatus?struct. This struct contains information about how many bytes have been downloaded and how many bytes still need to be downloaded. The?DownloadStatus.Percent?reports the percentage of bytes downloaded.譯：GetDownloadStatus 方法返回一個 DownloadStatus 結(jié)構(gòu)體，該結(jié)構(gòu)體包含已下載的字節(jié)數(shù)和尚需下載的字節(jié)數(shù)等信息。DownloadStatus.Percent 屬性報告已下載字節(jié)數(shù)的百分比

• AsyncOperationHandle.PercentComplete?returns an equally-weighted aggregate percentage of all the sub-operations that are complete. For example, if an operation has five sub-operations, each of them represents 20% of the total. The value doesn't factor in the amount of data that must be downloaded by the individual sub-operations.譯：AsyncOperationHandle.PercentComplete 方法返回所有子操作完成的等權(quán)重聚合百分比。例如，如果一個操作有五個子操作，每個子操作代表總進度的 20%，該值不考慮每個子操作需要下載的數(shù)據(jù)量。

For example, if you called?Addressables.DownloadDependenciesAsync?and five AssetBundles needed to be downloaded, GetDownloadStatus would tell you what percentage of the total number of bytes for all sub-operations had been downloaded so far. PercentComplete would tell you what percentage of the number of operations had finished, regardless of their size.

譯：例如，如果您調(diào)用 Addressables.DownloadDependenciesAsync，需要下載五個 AssetBundle，則 GetDownloadStatus 方法會告訴您迄今為止已下載了所有子操作的總字節(jié)數(shù)的百分比。而 PercentComplete 方法會告訴您已完成的操作數(shù)的百分比，而不考慮它們的大小

On the other hand, if you called?LoadAssetAsync, and one bundle had to be downloaded before an asset could be loaded from it, the download percentage might be misleading. The values obtained from GetDownloadStatus would reach 100% before the operation finished, because the operation had additional sub-operations to conduct. The value of PercentComplete would be 50% when the download sub-operation finished and 100% when the actual load into memory was complete.

譯：另一方面，如果您調(diào)用 LoadAssetAsync，需要從一個 bundle 中下載資產(chǎn)，下載進度可能會誤導。在下載子操作完成之前，從 GetDownloadStatus 方法獲得的值將達到 100%，因為操作需要進行其他子操作。而當下載子操作完成時，PercentComplete 的值將為 50%，當實際加載到內(nèi)存中時，該值將為 100%。在Unity Addressable系統(tǒng)中，用戶正在嘗試從遠程服務器下載預制件并在加載屏幕上報告其下載進度。他們在其協(xié)程中使用 while 循環(huán)來更新進度條，并嘗試在網(wǎng)上尋找解決方案來修復其代碼，但沒有成功。當單擊按鈕時，另一個腳本會調(diào)用 DownloadAsset 函數(shù)。作者希望獲得任何提示或建設性的批評來幫助解決他們的問題