Android: Handling back button during asynctask

Question

I have an Activity that shows a listview. On item click a second activity is started which runs an AsyncTask that fetches a remote URL based on which item is clicked, parses the results, then displays those results into another list view. While the async task is running I have a "loading" view that just displays an image and text. The problem is if I initiate the activity that runs the async task, then press back and start another instance of said activity, I get a force close.

I have tried

private class getlist extends AsyncTask implements OnDismissListener{
     ...
     @Override
     public void onDismiss(DialogInterface arg0) {
          this.cancel(true);
     }
}

But the problem persists.

I have also put

if(!isCancelled()){
  setContentView(R.layout.list);
  ...
  etc.

}

into my onPostExecute call, but either this is not preventing the view from being switched, or the problem is something else.

logcat shows "unexpected resume while already resumed .. got RemoteException sending setActive(false) notification" Then a bit further down in the log, "java.net.SocketTimeoutException: Socket is not connected"

How can I resolve this?

update:

E/AndroidRuntime(19379): Uncaught handler: thread AsyncTask #2 exiting due to uncaught exception
E/AndroidRuntime(19379): java.lang.RuntimeException: An error occured while executing doInBackground()
E/AndroidRuntime(19379):        at android.os.AsyncTask$3.done(AsyncTask.java:200)
E/AndroidRuntime(19379):        at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
E/AndroidRuntime(19379):        at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
E/AndroidRuntime(19379):        at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
E/AndroidRuntime(19379):        at java.util.concurrent.FutureTask.run(FutureTask.java:137)
E/AndroidRuntime(19379):        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1068)
E/AndroidRuntime(19379):        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:561)
E/AndroidRuntime(19379):        at java.lang.Thread.run(Thread.java:1096)
E/AndroidRuntime(19379): Caused by: java.lang.NullPointerException
E/AndroidRuntime(19379):        at com.metatroid.android.swim.ThreadViewer.getPosts(ThreadViewer.java:153)
E/AndroidRuntime(19379):        at com.metatroid.android.swim.ThreadViewer$getlist.doInBackground(ThreadViewer.java:70)
E/AndroidRuntime(19379):        at com.metatroid.android.swim.ThreadViewer$getlist.doInBackground(ThreadViewer.java:1)
E/AndroidRuntime(19379):        at android.os.AsyncTask$2.call(AsyncTask.java:185)
E/AndroidRuntime(19379):        at java.util.concurrent.FutureTask$Sync.innerRun

Your error, if you are reading LogCat correctly, has nothing to do with any of this, but rather is a network problem when you are trying to download the data. — CommonsWare
@CommonsWare - I've updated the question with what I believe is the correct trace — aperture

aperture aperture · Accepted Answer · 2011-04-09T12:56:34

The actual solution to this problem was to use ThreadSafeClientConnManager for the ClientConnectionManager

e.g.

BasicHttpParams params = new BasicHttpParams();
SchemeRegistry schemeRegistry = new SchemeRegistry();
schemeRegistry.register(new Scheme("http", PlainSocketFactory.getSocketFactory(), 80));
final SSLSocketFactory sslSocketFactory = SSLSocketFactory.getSocketFactory();
schemeRegistry.register(new Scheme("https", sslSocketFactory, 443));
ClientConnectionManager cm = new ThreadSafeClientConnManager(params, schemeRegistry);
DefaultHttpClient httpclient = new DefaultHttpClient(cm, params);

Android: Handling back button during asynctask

2 Answers