Does AsyncTask works simultaneously?

Issue

Does AsyncTask works simultaneously or first come first served manner? .

For example i've 3 AsyncTasks that have same interface class and same listener functions. Executing 3 AsyncTasks at same time. Which response from AsyncTasks will shows in listener function?

Doubts:

1. Does AsyncTasks run parallel or first come first served manner? 2. If AsyncTasks run parallel manner how to handle same listener function for all AsyncTasks?

Nb: Doubt 2 is because first response recieving while doing multiple requests at same time without using AsyncTask. (Web Api response).

Thanks in advance.

Solution

For multiple request you can use ThreadPoolExecutor

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
    new callApi().executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, location);
} else {
    new callApi().execute(location);
}

Thread Pool Pattern

AsyncTask uses a thread pool pattern for running the stuff from doInBackground()

The Thread pool Pattern is where number of Threads are created to perform a number of Tasks. It is basically a container where multiple threads come in a queue for different task.

For Example:

public class MultipleAsyncTask extends Activity
{
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        runMultipleAsyncTask(); // Start Async Task
    }
    private void runMultipleAsyncTask() // Run Multiple Async Task
    {
        FirstAsyncTask asyncTask = new FirstAsyncTask(); // First
        if(AppUtil.isCurrentVersionHoneycombAndAbove()) // Above Api Level 13
        {
            asyncTask.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
        }
        else // Below Api Level 13
        {
            asyncTask.execute();
        }
        SecondAsyncTask asyncTask2 = new SecondAsyncTask(); // Second
        if(AppUtil.isCurrentVersionHoneycombAndAbove())// Above Api Level 13
        {
            asyncTask2.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
        }
        else // Below Api Level 13
        {
            asyncTask2.execute();
        }
    }
    //Start First Async Task:
    private class FirstAsyncTask extends AsyncTask<Void, Void, Void>
    {
        @Override
        protected void onPreExecute()
        {
            Log.i("AsyncTask" ,"FirstOnPreExecute()");
        }
        @Override
        protected Void doInBackground(Void... params)
        {
            for(int index = 0; index < 50; index++)
            {
                Log.i("AsyncTask" ,"FirstAsyncTask");
                try
                {
                    Thread.sleep(100);
                }
                catch (InterruptedException exception)
                {
                    exception.printStackTrace();
                }
            }
            return null;
        }
        @Override
        protected void onPostExecute(Void result)
        {
            Log.d("AsyncTask" ,"FirstonPostExecute()");
        }
    }
    //Start Second Async Task:
    private class SecondAsyncTask extends AsyncTask<Void, Void, Void>
    {
        @Override
        protected void onPreExecute()
        {
            Log.i("AsyncTask" ,"SecondOnPreExecute()");
        }
        @Override
        protected Void doInBackground(Void... params)
        {
            for(int index = 0; index < 50; index++)
            {
                Log.d("AsyncTask" ,"SecondAsyncTask");
                try
                {
                    Thread.sleep(100);
                }
                catch (InterruptedException exception)
                {
                    exception.printStackTrace();
                }
            }
            return null;
        }
        @Override
        protected void onPostExecute(Void result)
        {
            Log.d("AsyncTask" ,"SecondOnPostExecute()");
        }
    }
}

Output:

FirstOnPreExecute()
SecondOnPreExecute()
FirstAsyncTask
SecondAsyncTask
FirstAsyncTask
SecondAsyncTask
FirstAsyncTask
SecondAsyncTask
FirstAsyncTask
SecondAsyncTask
FirstAsyncTask
SecondAsyncTask
FirstAsyncTask
SecondAsyncTask
FirstAsyncTask
SecondAsyncTask
FirstAsyncTask
SecondAsyncTask
FirstAsyncTask
SecondAsyncTask
FirstAsyncTask
SecondAsyncTask
FirstonPostExecute()
SecondOnPostExecute()

Same asyncTask for different functions like api requests:

boolean flag;
    @Override
    protected String doInBackground (String... params) {
        flag= params[0].endsWith("/repos");
        //other statements
    }

Now in your onPostExecute:

if(flag){
    //parse one way
} else {
    //parse another way
}

Answered By - Hemant Parmar