Fragment Crash on Activity destroyed

Question

I am facing this particular crash on few devices

Fatal Exception: java.lang.RuntimeException: An error occurred while executing doInBackground()
       at android.os.AsyncTask$3.done(AsyncTask.java:309)
       at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:354)
       at java.util.concurrent.FutureTask.setException(FutureTask.java:223)
       at java.util.concurrent.FutureTask.run(FutureTask.java:242)
       at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:234)
       at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
       at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
       at java.lang.Thread.run(Thread.java:818)
Caused by java.lang.IllegalStateException: Activity has been destroyed
       at android.support.v4.app.FragmentManagerImpl.enqueueAction(FragmentManager.java:1515)
       at android.support.v4.app.BackStackRecord.commitInternal(BackStackRecord.java:634)
       at android.support.v4.app.BackStackRecord.commitAllowingStateLoss(BackStackRecord.java:617)
       at net.trellisys.papertrell.components.mediagallery.MGBaseActivity$initQuickControls.doInBackground(MGBaseActivity.java:136)
       at net.trellisys.papertrell.components.mediagallery.MGBaseActivity$initQuickControls.doInBackground(MGBaseActivity.java:1)
       at android.os.AsyncTask$2.call(AsyncTask.java:295)
       at java.util.concurrent.FutureTask.run(FutureTask.java:237)
       at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:234)
       at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
       at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
       at java.lang.Thread.run(Thread.java:818)

What I am doing is am loading a Fragment to an Activity using an Async method.

I can not recreate this error in my side but have seen this issue in many devices. Can any one help me out with this error?

Here's the code snippet :-

public class initQuickControls extends AsyncTask<String,Void,String> {
    String fromPage = "";
    public initQuickControls(String from){
        fromPage = from;
    }
     QuickControlsFragment quicFrag = null;
   @Override
   protected String doInBackground(String... strings) {
       quicFrag = new QuickControlsFragment(fromPage);
       FragmentManager fragManager = getSupportFragmentManager();
       fragManager.beginTransaction().replace(R.id.quickcontrols_container,quicFrag).commitAllowingStateLoss();
       return "EXECUTED";
   }

   protected void onPostExecute(String result) {}
}

And this is how I am calling the Fragment :-

new initQuickControls("List").execute("");

Answer 1

First of all you should be familiar with the activity lifecycle .
I think that your AsynkTask finishes when activity is destroyed and that's why you cannot perform any fragment transaction. You may add condition before this transaction:

if (!MainActivity.this.isFinishing()) {...}

Hope it'll help.

But if you're using AsynkTask only to add fragment - this is incorrect. Just add your fragment in the onCreate method without any additional code.

edit:

You cannot perform UI operations in the doInBackground method because it's running not in the UI thread. Move Ui-specific code to onPostExecute method and it'll work. And do not forget about isFinishing() condition. Also you should cancel all your AsyncTasks in Activity.onBackPressed() method to avoid such problems.