在Android?中存儲數據時經常用SharedPreference, 并且在提交數據時一直用的是Editor的commit（API 1中的方法）, 系統用了apply（API 9中的方法）,看了方法的介紹, 原來這個方法也是可以提交數據的.

原文地址：https://developer.android.com/reference/android/content/SharedPreferences.Editor.html

apply方法在官方SDK說明如下：

apply

Added in API level 9
void apply ()
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().

commit

Added in API level 1
boolean commit ()
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 commit wins.
If you don't care about the return value and you're using this from your application's main thread, consider using apply() instead.

這兩個方法的區別在于：?
1. apply沒有返回值而commit返回boolean表明修改是否提交成功?
2. apply是將修改數據原子提交到內存, 而后異步真正提交到硬件磁盤, 而commit是同步的提交到硬件磁盤，因此，在多個并發的提交commit的時候，他們會等待正在處理的commit保存到磁盤后在操作，從而降低了效率。而apply只是原子的提交到內容，后面有調用apply的函數的將會直接覆蓋前面的內存數據，這樣從一定程度上提高了很多效率。?
3. apply方法不會提示任何失敗的提示。?
由于在一個進程中，sharedPreference是單實例，一般不會出現并發沖突，如果對提交的結果不關心的話，建議使用apply，當然需要確保提交成功且有后續操作的話，還是需要用commit的。

總結

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