How to pass Object of Service to MyActivity?

Question

First of all: I am bigger in Android programming

I have created simple TCP Socket using Service.

The client connects to server when the button in MainActivity is triggered.

Now i want to create PrintWriter object in MainActivity using Socket object of Service.

I got to know it is possible to pass objects from Service to Activity using JSON.

I searched over Internet but couldn't get an idea how I can pass it.

Please give me simple code example to pass the object.

MyService.java

public class MyService extends Service{
public static Socket clientsocket;
public static PrintWriter printer;
SendMessage sender;

@Override
public void onCreate() {
Toast.makeText(this, "Created", Toast.LENGTH_LONG).show();
super.onCreate();
}

@Override
public void onDestroy() {
Toast.makeText(this, "Stoped", Toast.LENGTH_LONG).show();
if(clientsocket!=null){
        try{
        clientsocket.close(); 
        Toast.makeText(this, "Socket Closed", Toast.LENGTH_LONG).show();
        }catch(IOException e){
            e.printStackTrace();
        }
    }
  }

@Override
public int onStartCommand(Intent intent, int flags, int startId) {
    Toast.makeText(this, "Running", Toast.LENGTH_LONG).show();
    SendMessage sender=new SendMessage();
    sender.execute();
    return super.onStartCommand(intent, flags, startId);
}

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

class SendMessage extends AsyncTask<Void, Void, Void>{

    @Override
    protected Void doInBackground(Void... params) {
        try {
            clientsocket = new Socket("192.168.237.1", 6666);
        } catch (UnknownHostException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

    @Override
    protected void onPostExecute(Void result) {
        if(clientsocket!=null){
            Toast.makeText(MyService.this, "Connected", Toast.LENGTH_LONG).show();
        }else{
            Toast.makeText(MyService.this, "Lost Connection", Toast.LENGTH_LONG).show();
        }
        super.onPostExecute(result);
    }

   }}

MainActivity.java

public class MainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

}

public void start(View v){
    startService(new Intent(this,MyService.class));
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
     getMenuInflater().inflate(R.menu.main, menu);
     return true;
}

class PrintMessage extends AsyncTask<Void, Void, Void>{

    @Override
    protected Void doInBackground(Void... arg0) {
        return null;
    }
}

@Override
protected void onDestroy() {
    stopService(new Intent(this,MyService.class));
    super.onDestroy();
}}

Now I need a clear & complete code for both MyService.java (how to pass object I.e. in this case Socket object clientsocket )and MainActivity.java (how to retreive passed object I.e. clientsocket and use it to create PrintWriter object)

Answer 1

Please consider using an event bus library, like greenrobot EventBus :-) Those work wonders when it comes to passing data between the elements of the app and are pretty safe to use.

Answer 2

I personally would use the following solution How to send event from Service to Activity with Otto event bus? with Otto Event Bus, and just send an instance of the class with the data in it.

public class MainActivity extends ActionBarActivity
{

    @Override
    protected void onResume()
    {
        super.onResume();
        SingletonBus.INSTANCE.getBus().register(this);
    }

    @Override
    protected void onPause()
    {
        SingletonBus.INSTANCE.getBus().unregister(this);
        super.onPause();
    }
    ...
}

And

// you might need to change this as linked in the above link: 
// https://stackoverflow.com/questions/15431768/how-to-send-event-from-service-to-activity-with-otto-event-bus
public enum SingletonBus
{
    INSTANCE;

    private Bus bus;

    private SingletonBus()
    {
        this.bus = new Bus(ThreadEnforcer.ANY);
    }

    public Bus getBus()
    {
        return bus;
    }
}

and

public class MyEvent
{
    private Data data;

    public MyEvent(Data data)
    {
        this.data = data;
    }

    public Data getData()
    {
        return data;
    }
}

and

SingletonBus.INSTANCE.getBus().post(new MyEvent(data));