SharedPreferences.Editor 的commit方法与apply方法的区别

最新推荐文章于 2020-06-04 17:03:44 发布

转载最新推荐文章于 2020-06-04 17:03:44 发布 · 1.6k 阅读

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本文详细介绍了Android中SharedPreferences的使用方法，对比了apply()与commit()两个关键方法的区别。apply()方法会立即更新内存中的数据但异步写入磁盘，不通知失败情况；commit()则同步将更改写入持久化存储并返回是否成功。

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public abstract void apply ()

Added in API level 9

Commit your preferences changes back from this Editor to the SharedPreferences object it is editing. This atomically performs the requested modifications, replacing whatever is currently in the SharedPreferences.

Note that when two editors are modifying preferences at the same time, the last one to call apply wins.

Unlike commit(), which writes its preferences out to persistent storage synchronously, apply() commits its changes to the in-memory SharedPreferences immediately but starts an asynchronous commit to disk and you won't be notified of any failures. If another editor on this SharedPreferences does a regular commit() while a apply() is still outstanding, the commit() will block until all async commits are completed as well as the commit itself.

As SharedPreferences instances are singletons within a process, it's safe to replace any instance of commit() with apply() if you were already ignoring the return value.

You don't need to worry about Android component lifecycles and their interaction with apply() writing to disk. The framework makes sure in-flight disk writes from apply()complete before switching states.

The SharedPreferences.Editor interface isn't expected to be implemented directly. However, if you previously did implement it and are now getting errors about missing apply(), you can simply call commit() from apply().