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POCan't cancel running AsyncTask
 

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  1. POCan't cancel running AsyncTask
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    <p>I'm having some trouble with an AsyncTask subclass.</p> <p>I have a main activity as below that displays a button and a number that counts up on the screen. Clicking the button launches an Edit activity where a number can be entered.</p> <p>The number displayed on the Main activity should update with the timer which it does but the trouble I'm having is that I can't stop the timer. It should stop when entering the Edit activity and returning from it as well, as well as restart with the a new value too but it doesn't, the timer is always running with the first entered value, it never stops, even when I leave the program and return to the home screen.</p> <p>I've looked at posts here such as <a href="https://www.google.com/url?sa=t&amp;rct=j&amp;q=&amp;esrc=s&amp;source=web&amp;cd=1&amp;ved=0CCgQFjAA&amp;url=https://stackoverflow.com/questions/14279695/cant-cancel-async-task-in-android&amp;ei=7-e3UqT7I4jikgWks4H4CQ&amp;usg=AFQjCNH2wCR_MzkUyb4w1e3JC2wcI21HLg&amp;bvm=bv.58187178,d.dGI&amp;cad=rja" rel="nofollow noreferrer">Can't cancel Async task in android</a> but they all just mention checking for isCancelled() which I'm doing. Can anyone see/explain why I can't stop this AsyncTask ?</p> <pre><code>public class MainActivity extends Activity { @Override UpdateTimer ut; TextView tvn; protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); } @Override public void onResume() { super.onResume(); tvn = (TextView) findViewById(R.id.numDisplay); if(ut != null )//&amp;&amp; ut.getStatus() == AsyncTask.Status.RUNNING) { ut.cancel(true); ut.cancelled = true; Log.d("-----M_r","called cancel: "+ut.isCancelled()+" "+cancelled); } if (updateRequired) { ut = new UpdateTimer(); ut.execute(number); updateRequired = false; } } public void onEditButtonPressed(View caller) { // kill any running timer if(ut != null ) { ut.cancel(true); ut.cancelled = true; } // start the edit screen Intent e_intent = new Intent(this, EditActivity.class); startActivity(e_intent); } private void updateScreen(long number) { // update screen with current values tvn.setText("" + number); } private class UpdateTimer extends AsyncTask&lt;Long, Long, Integer&gt; { long number; public boolean cancelled; @Override protected Integer doInBackground(Long... params) { number = params[0]; cancelled = false; while(true) { number += 1; //sleep for 1 second try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } // tell this AsyncTask to update the time on screen publishProgress(number); // check if timer needs to stop if (isCancelled()) break; if(cancelled) break; } return null; } protected void onProgressUpdate(Long... progress) { Log.d("-----M_ut","updated: "+number+" "+this.isCancelled()+" "+cancelled); updateScreen(progress[0]); } protected void onCancelled(Integer result) { cancelled = true; Log.d("-----M_ut","-- cancelled called: "+this.isCancelled()); } } protected void onStop() { super.onStop(); // kill any running timer if(ut != null) { ut.cancel(true); } } </code></pre> <p>}</p>
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