java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()

翻译于 2017-03-16 16:08:45 发布 · 333 阅读

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本文介绍了如何避免在Android应用中因在非UI线程尝试更新UI而引发的java.lang.RuntimeException错误。通过使用runOnUiThread方法确保所有UI更新操作都在主线程中执行。

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java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()

Worker threads are meant for doing background tasks and you can't show anything on UI within a worker thread unless you call method like runOnUiThread. If you try to show anything on UI thread without calling runOnUiThread, there will be a java.lang.RuntimeException.

So, if you are in an activity but calling Toast.makeText() from worker thread, do this:

runOnUiThread(new Runnable() 
{
   public void run() 
   {
      Toast toast = Toast.makeText(getApplicationContext(), "Something", Toast.LENGTH_SHORT).show();    
   }
});

The above code ensures that you are showing the Toast message in a UI thread since you are calling it inside runOnUiThread method. So no more java.lang.RuntimeException