Android: Cancel Async Task?

From SDK: Cancelling a task A task can be cancelled at any time by invoking cancel(boolean). Invoking this method will cause subsequent calls to isCancelled() to return true. After invoking this method, onCancelled(Object), instead of onPostExecute(Object) will be invoked after doInBackground(Object) returns.To ensure that a task is cancelled as quickly as possible, you should always check the return value of isCancelled() periodically from doInBackground(Object), if possible (inside a loop for instance.

) So your code is right for dialog listner: uploadingDialog. SetOnCancelListener(new DialogInterface. OnCancelListener(){ public void onCancel(DialogInterface dialog) { myTask.

Cancel(true); //finish(); } }) Now, as I have mentioned earlier from SDK, you have to check whether the task is cancelled or not, for that you have to check isCancelled() inside the onPreExecute() method For example: if (isCancelled()) break; else { // do your work here }.

From SDK: Cancelling a task A task can be cancelled at any time by invoking cancel(boolean). Invoking this method will cause subsequent calls to isCancelled() to return true. After invoking this method, onCancelled(Object), instead of onPostExecute(Object) will be invoked after doInBackground(Object) returns.To ensure that a task is cancelled as quickly as possible, you should always check the return value of isCancelled() periodically from doInBackground(Object), if possible (inside a loop for instance.

) So your code is right for dialog listner: uploadingDialog. SetOnCancelListener(new DialogInterface. OnCancelListener(){ public void onCancel(DialogInterface dialog) { myTask.

Cancel(true); //finish(); } }); Now, as I have mentioned earlier from SDK, you have to check whether the task is cancelled or not, for that you have to check isCancelled() inside the onPreExecute() method. For example: if (isCancelled()) break; else { // do your work here }.

Yes I agree with you, but the thing is that I don't use a loop on my doInBackground. I just use some commands to upload an image via ftp. So I'm wondering, does it matter to check whether the task is cancelled or not before I send the image, like you said?

– mole363 May 19 at 15:46 @mole363, you have to just check whether the task is cancelled or not by using isCancelled() inside the doInBackground method. – Paresh Mayani May 20 at 5:07.

Create some member variables in your activity like YourAsyncTask mTask; Dialog mDialog; use these for your dialog and task; in onPause() simply call if(mTask! =null) mTask.cancel(); if(mDialog! =null) mDialog.dismiss().

You can just ask for cancellation but not really terminate it. See this answer.

I spent a while figuring this out, all I wanted was a simple example of how to do it, so I thought I'd post how I did it. This is some code that updates a library and has a progress dialog showing how many books have been updated and cancels when a user dismisses the dialog: private class UpdateLibrary extends AsyncTask{ private ProgressDialog dialog = new ProgressDialog(Library. This); private int total = Library.instance.appState.

GetAvailableText(). Length; private int count = 0; //Used as handler to cancel task if back button is pressed private AsyncTask updateTask = null; @Override protected void onPreExecute(){ updateTask = this; dialog. SetProgressStyle(ProgressDialog.

STYLE_HORIZONTAL); dialog. SetOnDismissListener(new OnDismissListener() { @Override public void onDismiss(DialogInterface dialog) { updateTask. Cancel(true); } }); dialog.

SetMessage("Updating Library..."); dialog. SetMax(total); dialog.show(); } @Override protected Boolean doInBackground(Void... arg0) { for (int I = 0; I Length;i++){ if(isCancelled()){ break; } //Do your updating stuff here } } @Override protected void onProgressUpdate(Integer... progress){ count += progress0; dialog. SetProgress(count); } @Override protected void onPostExecute(Boolean finished){ dialog.dismiss(); if (finished) DialogHelper.

ShowMessage(Str. TEXT_UPDATELIBRARY, Str. TEXT_UPDATECOMPLETED, Library.

Instance); else DialogHelper. ShowMessage(Str. TEXT_UPDATELIBRARY,Str.

TEXT_NOUPDATE , Library. Instance); } }.

FOUND THE SOLUTION: I added an action listener before uploadingDialog.show() like this: uploadingDialog. SetOnCancelListener(new DialogInterface. OnCancelListener(){ public void onCancel(DialogInterface dialog) { myTask.

Cancel(true); //finish(); } }); That way when I press the back button, the above OnCancelListener cancels both dialog and task. Also you can add finish() if you want to finish the whole activity on back pressed. Remember to declare your async task as a variable like this: MyAsyncTask myTask=null; and execute your async task like this: myTask = new MyAsyncTask(); myTask.execute().

– Paresh Mayani Oct 12 at 5:04 You don't have to set the cancel listener so overtly before showing the dialog, there's a show method which accepts a cancel listener as one of its parameters. – SK9 Nov 13 at 11:12.

FOUND THE SOLUTION: I added an action listener before uploadingDialog.show() like this.

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