private CustomTask mTask;

@Override
public void onActivityCreated(Bundle savedInstanceState)
{
	super.onActivityCreated(savedInstanceState);
	if(this.mTask == null)
	{
		this.mTask = new CustomTask ()
		{
			@Override
			protected void onPostExecute(Response result)
			{
				//Your stuff
				Fragment.this.mTask = null;
			}
	
			@Override
			protected void onCancelled()
			{
				Fragment.this.mTask = null;
			}
		};
		this.mTask.ExecuteCompat();
	}
}

@Override
public void onDestroyView()
{
	if (this.mTask != null && this.mTask.getStatus() != AsyncTask.Status.FINISHED)
		this.mTask.cancel(true);
	super.onDestroy();
}