两个不同的AsyncTasks不从前台服务开始

Question

I have written a foreground service which in the onCreate method does this:

public void onCreate(){
     //........
     startForeground(id,notification);
     Task1=new Task(this);
     task1.execute();
     Task2=new Task(this);
     Log.d("T2","Created");
     task2.execute();
     Log.d("T2","Executed");
}

Now what is happening is that above code is causing task1 to execute(which has a while(true) with sleep of 60 sec after each loop), but never lets task2 start its doInBackground().

I am not sure whats wrong.As per the logcat, its clearly showing that the task2.execute() does get invoked.But why is the doInBackground() of second task is not getting started? I was initially planning to have two foreground services, but after reading a few SO posts, decided to have only one Service in foreground and let it have two different Asynctasks to do some continuous processing in background. Please help me in making this work!

Answer 1

The default executor for AsyncTask , starting from Honeycomb, is AsyncTask.SERIAL_EXECUTOR , which means that only one task is executing at a given time.

If you need parallelism, just use AsyncTask.THREAD_POOL_EXECUTOR , ie

task.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, params);

instead of just

task.execute(params);

See the Order of Execution section in the documentation for AsyncTask .

Answer 2

It`s simply because since from Android 3.0 AsyncTask-s work in a single background thread:

Starting with HONEYCOMB, tasks are executed on a single thread to avoid common application errors caused by parallel execution.

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

So Task2 never run because you run it before a completion of Task1.