onPostExecute上取消的AsyncTask [英] onPostExecute on cancelled AsyncTask

问题描述

确实 onPostExecute 执行，如果的AsyncTask 已被取消？

Does onPostExecute execute if the AsyncTask has been cancelled?

如果它确实执行，它是安全地说，我应该总是问，如果该任务已经被取消（ isCancelled ）的的开始onPostExecute ，做其他事情之前？

If it does execute, is it safe to say that I should always ask if the task has been cancelled (isCancelled) at the start of onPostExecute, before doing anything else?

推荐答案

onPostExecute对取消记录的行为（）是Android的2和Android 4之间变化。

The documented behaviour of onPostExecute on cancel() was changed between Android 2 and Android 4.

<一个href="http://grep$c$c.com/file/repository.grep$c$c.com/java/ext/com.google.android/android/2.3.7_r1/android/os/AsyncTask.java#AsyncTask.onPostExecute%28java.lang.Object%29">Android 2.3.7 onPostExecute ：

运行doInBackground后在UI线程上。指定的结果是   通过doInBackground返回的值或空，如果任务被取消   或异常发生。

Runs on the UI thread after doInBackground. The specified result is the value returned by doInBackground or null if the task was cancelled or an exception occured.

<一个href="http://grep$c$c.com/file/repository.grep$c$c.com/java/ext/com.google.android/android/4.0.1_r1/android/os/AsyncTask.java#AsyncTask.onPostExecute%28java.lang.Object%29">Android 4.0.1 onPostExecute ：

运行doInBackground后在UI线程上。指定的结果是   通过doInBackground返回的值。此方法将不被调用，如果   任务被取消。

Runs on the UI thread after doInBackground. The specified result is the value returned by doInBackground. This method won't be invoked if the task was cancelled.

所以，如果你还在针对Android的2台设备，你应该假设onPostExecute将被调用，在onPostExecute检查空的结果。

So if you are still targeting Android 2 devices you should assume that onPostExecute will be called and in onPostExecute check for null result.

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