Stop Asynctask Doinbackground Method

Stop AsyncTask doInBackground method

public final boolean cancel (boolean mayInterruptIfRunning)

Attempts to cancel execution of this task. This attempt will fail if the task has already completed, already been cancelled, or could not be cancelled for some other reason. If successful, and this task has not started when cancel is called, this task should never run. If the task has already started, then the mayInterruptIfRunning parameter determines whether the thread executing this task should be interrupted in an attempt to stop the task.

Use isCancelled()

public final boolean isCancelled ()

Returns true if this task was cancelled before it completed normally. If you are calling cancel(boolean) on the task, the value returned by this method should be checked periodically from doInBackground(Object[]) to end the task as soon as possible.

Android - Cancel AsyncTask Forcefully

Check the accepted answer and the answer by commonsware in the above link

Stop AsyncTask doInBackground Method in Android

The "can't re-execute task" error can be solved by creating a new instance of the AsyncTask. You can't call execute twice on the same instance, but you can make as many instances as you want.

Stopping the execution won't help that error. The problem isn't that its currently running, the problem is that you need to create a new instance and run that instead.

How to cancel doInBackground in AsyncTask

if (doc == null) {
  return null;
}

and onPostExecute check if xmlItems is null. If it is null show the Toast

Android how to stop AsyncTask

The cancel(...) method prevents the call of onPostExecute() after doInBackground() finishes. Instead onCancelled() will be invoked. Furthermore isCancelled() will return true as soon as you call cancel(). You should check for this in your doInBackground(), to be able to let it finish ASAP.

So, this is useless code:

@Override
protected void onCancelled() {
    super.onCancelled();
    cancel(true);
}

cancel(true) has no effect here, because onCancelled() will only be invoked if you call cancel() before. You can leave it empty or deal with the situation here if your AsyncTask will be canceled.

Here you should check for isCancelled():

 @Override
 protected Boolean doInBackground(Void... params) {
     return null;
 }

Because you do nothing here your AsyncTask is useless, because you do no background threading at all.

This is the wrong place to call isCancelled():

@Override
protected void onPreExecute() {

    if (!isCancelled()){
        ...
    }

Again, isCancelled() should be checked in doInBackground() to let it finish ASAP.

To cancel your Task by switching Activities or an Activity goes to background, use the onPause() callback and call mTask.cancel(true);
Read the docs about the AsyncTask carefully again to get the basics.

How to cancel or stop AsyncTask?

On your button click write the code

task.cancel(true);

where task is the reference of the async task you have created and started

How to stop AsyncTask ? why it does not stop when calling finish method?

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.)

Put below code inside loop in doInBackground(Object[]) method.

if (isCancelled()) break;

Please see below link for more details...

http://developer.android.com/reference/android/os/AsyncTask.html

Edit:

 while ((aux = reader.readLine()) != null) {
    builder.append(aux);
    if (isCancelled()) break;
 }