Start AsyncTask from another AsyncTask doInBackground()

Question

I'm trying to start an AsyncTask from another AsyncTask's doInBackground()-method...

Is this even possible? If yes, how can I achieve this?

LATER EDIT:

The idea is that I start an asynctask that will get me statuses from Tweeter ... Everything ok until here ... But when I encounter some specific tweets I need to modify them with some info from my server, here I will make another network operation, and since I need to wait until I get the info from my server I do:

GetContent getContentServiceAsyncTask = new GetContent(context);
try {
    tweetText = Uri.decode(getContentServiceAsyncTask.execute(
            URL_GET_CONTENT, jsonRequest).get());
} catch (InterruptedException e) {
    Log.e(TAG_DEBUG, "InterruptedException: ", e);
} catch (ExecutionException e) {
    Log.e(TAG_DEBUG, "ExecutionException: ", e);
}

This is started from the allready started AsyncTask in doInBackground() method ...

I know I can just add the methods in the AsyncTask and just call them in the doInBackground() method, but I need to use them in other places, where I start these AsyncTasks from onPostExecute ...

If you guys think there is an easy work-around for this, that won't affect my performance, that will be great ... if not I will make some static methods that I will call in all the AsyncTasks I need(but this will require me to modify a lot of my code)

Answer 1

According to the post below you can do Activity.runOnUiThread() to run a Runnable on the main-Thread (from another thread).

• Running code in main thread from another thread

So theoretically you could do this:

• Run the Async Task
• do Activity.runOnUiThread(Runnable) inside your AsyncTask and start a new AsyncTask from inside of this runnable

As the name says Activity.runOnUiThread() executes the runnable on the main-thread

But it's kind of hacky.

Code should look something like this: (didnt test)

// first task
    (new AsyncTask<String, String, String>() {

        @Override
        protected String doInBackground(String... params) {
            ParentActitity.this.runOnUiThread(new Runnable() {

                @Override
                public void run() {
                    //second async stared within a asynctask but on the main thread
                    (new AsyncTask<String, String, String>() {

                        @Override
                        protected String doInBackground(String... params) {
                            // TODO Auto-generated method stub
                            return null;
                        }

                    }).execute();

                }
            });
            return null;
        }

    }).execute();

This nested example is not a good style to use in production because (IMHO) its close to unreadable.

Additional Notes:

Activity.runOnUiThread(Runnable) is not static! Thats why my example uses ParentActivity(.this).runOnUiThread(Runnable).

Answer 2

AsyncTasks are supposed to run from main (UI) thread. You should not run another AsyncTask from doInBackground because this method is executed on a non-UI thread.

In your case, I can suggest you two things:

1. Combine the processing of your both AsyncTaks in a single request
2. Launch your second AsyncTask from onPostExecute of your first task.