Is it possible to use AsyncTask in a Service class ?

Question

Everything is in the title.

On the official documentations it is stated that Note that services, like other application objects, run in the main thread of their hosting process and AsyncTask only works if it is executed in the UIThread.

So is it possible to use AsyncTask in a Service class?

I am trying to do so but I'm always getting the same error

05-01 18:09:25.487: ERROR/JavaBinder(270): java.lang.ExceptionInInitializerError

...

05-01 18:09:25.487: ERROR/JavaBinder(270): Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()

Am I doing something wrong or is this just impossible ?

Here is the code of my Service class

package com.eip.core;

import android.app.Service;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.IBinder;
import android.os.RemoteException;
import android.util.Log;

public class NetworkService extends Service {


    private final INetwork.Stub mBinder = new INetwork.Stub() {

        @Override
        public int doConnect(String addr, int port) throws RemoteException {
            new ConnectTask().execute("test42");
            return 0;
        }
    };

    @Override
    public IBinder onBind(Intent arg0) {
        return mBinder;
    }

    private class ConnectTask extends AsyncTask<String, Void, Void> {

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            Log.i("OnPreExecute()", "");
        }

        @Override
        protected Void doInBackground(String... arg0) {
            Log.i("doInBackground()", "");
            return null;
        }

        @Override
        protected void onPostExecute(Void result) {
            super.onPostExecute(result);
            Log.i("OnPostExecute()", "");
        }

    }
}

Answer 1

So is it possible to use AsyncTask in a Service class?

Absolutely! Here's an example.

Your error is because you are trying to use an AsyncTask from some other thread you forked, rather than the main application thread. Since AsyncTask does background work for you, you probably do not need that extra thread you are creating.

Answer 2

Also be sure to check out IntentService. If that class is sufficient for your needs, it will take care of a lot of little details involved in making that pattern work correctly.

Answer 3

Maybe problem is not AsyncTask but something else. For example are you sure your onBind method works correctly? Please try this:

@Override
public IBinder onBind(Intent arg0) {
    return null;
}

You could also try that

public class NetworkService extends Service{
  @Override
  public void onStart(Intent intent, int startId) {
    new ConnectTask().execute("test42");
  }
}

Answer 4

I Think I found why it is not working in my case.

Here I am using this :

private final INetwork.Stub mBinder = new INetwork.Stub() {

        @Override
        public int doConnect(String addr, int port) throws RemoteException {
            new ConnectTask().execute("test42");
            return 0;
        }
    };

I am using this to do what so called IPC, Inter Process Communication, so I guess that my Service and my Activity are in two differents process, AsyncTask must be executed in the main UI thread according to the android doc, so why I was trying to do seems to me just impossible according to those facts.

If I am wrong please someone can correct me.

Answer 5

I am facing the same issue: I have a callback from the service to the caller, which displays a UI, therefore, I would like the ASyncTask to work on that UI Thread. Looper.prepare, Looper.loop and Looper.quit seems a lead, but I haven't succeded yet.