Android: How to communicate and exchange objects with a Local Service

Question

So far I've a class for a simple local service. What I want to do is to send requests to this local service from different activies in my application. Depending on the parameters of these requests the service will connect via HttpClient to a webserver and receive a JSONObject and return it to the activity. All the HTTP communication is already working within my activity, but I'd like it to run in a separate thread in my local service now.

The source code of my very simple local service looks like this so far:

// BackgroundService.java
package com.test.localservice;

import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.util.Log;
public class BackgroundService extends Service
{
    @Override
    public void onCreate() {
        super.onCreate();
        Log.i("BackgroundService", "onCreate()");
        Thread thr = new Thread(null, new RunThread(), "BackgroundService");
        thr.start();
    }
    class RunThread implements Runnable
    {
        public void run() {
            Log.i("BackgroundService", "run()");

            /* Here the HTTP JSON communication is going to happen */

            //BackgroundService.this.stopSelf();
        }
    }
    @Override
    public void onDestroy()
    {
        Log.i("BackgroundService", "onDestroy()");
        super.onDestroy();
    }

    @Override
    public void onStart(Intent intent, int startId) {
        Log.i("BackgroundService", "onStart()");
        super.onStart(intent, startId);
    }
    @Override
    public IBinder onBind(Intent intent) {
        Log.i("BackgroundService", "onBind()");
        return null;
    }

}

The problem I'm facing now (due to a lack of knowledge) is the communication part Activities <--> Local Service. I found some communication and object exchange examples for a Remote Service using AIDL (Android Interface Definiton Language). However, I'm not sure if I've to go this path. I would simply like to exchange either my own defined objects or if that is not possible then just a JSONObject or if it makes things much easier even just simple String Arrays would work (for now).

Can someone please point me in the right direction and if possible give a simple example of an Object exchange (both ways) with a local service.

Thanks in advance.

Answer 1

I'd suggest using an AsyncTask instead of your own thread in this scenario.

To give an activity a reference to your BackgroundService object, your options are:

1. Use a singleton (i.e., make your BackgroundService object available from a static context, such as a public static data member, nulling out that static reference in onDestroy()).

2. Follow the LocalServiceBinding API sample to return an IBinder that simply gives access to the BackgroundService object.

From there, everything is in the same JVM, so you can just pass objects around. Be careful, though, not to hold onto anything past the component lifetime (e.g., Activity should not cache the singleton).