Wait for multiple AsyncTask to complete

Question

I am parallelizing my operation by splitting it in the exact number of cores available and then, by start the same number of AsyncTask, performing the same operation but on

Answer 1

First, add this class to your project

public abstract class MultiTaskHandler {
    private int mTasksLeft;
    private boolean mIsCanceled = false;

    public MultiTaskHandler(int numOfTasks) {
        mTasksLeft = numOfTasks;
    }

    protected abstract void onAllTasksCompleted();

    public void taskComplete()  {
        mTasksLeft--;
        if (mTasksLeft==0 && !mIsCanceled) {
            onAllTasksCompleted();
        }
    }

    public void reset(int numOfTasks) {
        mTasksLeft = numOfTasks;
        mIsCanceled=false;
    }

    public void cancel() {
        mIsCanceled = true;
    }
}

Then:

int totalNumOfTasks = 2; //change this to the number of tasks that you are running
final MultiTaskHandler multiTaskHandler = new MultiTaskHandler(totalNumOfTasks) {
    @Override
    protected void onAllTasksCompleted() {
       //put the code that runs when all the tasks are complete here
    }
};

Then in each task - when completed, add the line: multiTaskHandler.taskComplete();

Example:

(new AsyncTask() {

    @Override
    protected Void doInBackground(Void... voids) {
        // do something...
        return null;
    }

    @Override
    protected void onPostExecute(Void aVoid) {
        multiTaskHandler.taskComplete();
    }
}).execute();

You can use multiTaskHandler.cancel() if you want to cancel the code that runs when all the tasks have completed. For instance - if you have an error (don't forget to also cancel all the other tasks).

* This solution will not pause the main thread!