AIDL (Remote Service Binding )

2012-01-16T11:18:00.000-08:00

If you want to access the service of different process /Application from our application then we needs some IPC method because In Android normally processes does not access other process memory. Eg. User needs to user IPC method to access the Telephony Service. There are 2 method of IPC for Remote Service-

Messaging: - We will discuss this method in later posts.
AIDL (Android Interface Definition Language):-

In AIDL we create the .aidl file. This .aidl file contain an Interface with the methods that we want to access from our client application.

Steps to use AIDL :-

On Service side Create file with extension .aidl. In this file write an interface. Generally we keep this AIDL file in different package than the source file. Because the same AIDL file is needed in client side application.

package com.aidl;

interface IRemoteInterface

{

String getName();

void setName(String a);

}

If you create the aidl in right way then eclipse automatically create a java file in Gen folder.  This file works as Interface between client and server.

2- Create the Service class

package com.self;

import com.aidl.IRemoteInterface;

import android.app.Activity;

import android.app.Service;

import android.content.DialogInterface;

import android.content.Intent;

import android.content.DialogInterface.OnClickListener;

import android.os.Bundle;

import android.os.IBinder;

import android.os.RemoteException;

import android.util.Log;

import android.view.View;

import android.widget.Button;

import android.widget.TextView;

public class RemoteServer extends Service

{

String userName;

public void onCreate()

{

Log.i("RemoteServer","In onCreate");

}

public int onStartCommand(Intent intent, int flag, int statusID)

{

Log.i("RemoteServer","In onStartCommand");

return START_STICKY;

}

@Override

public IBinder onBind(Intent arg0) {

// TODO Auto-generated method stub

Log.i("RemoteServer","In onBind");

return mBinder;

}

private IRemoteInterface.Stub mBinder = new IRemoteInterface.Stub() {

@Override

public String getName() throws RemoteException {

// TODO Auto-generated method stub

return userName.toUpperCase();

}

@Override

public void setName(String a) throws RemoteException {

// TODO Auto-generated method stub

userName = a;

}

};

}

As you can see in the highlighted code we provide the definition of the aidl interface methods. Here we set the String using setName() and get the same capital String using getName(). As you can see when the client try to bind with service then onBind() returns the object of IRemoteInterface.stub object. This object is accessed in client side and using this mBinder object client access these two methods.

3- We copy same aidl file in client side in same package where it is created in Service side. Eg com.aidl.

Folder Structure

4- Now write the Client side code. Where we start and bind with the service. Here we will create an Activity and call the startService() and bindService()

package com.lge;

import com.aidl.IRemoteInterface;

import android.app.Activity;

import android.content.ComponentName;

import android.content.Context;

import android.content.Intent;

import android.content.ServiceConnection;

import android.os.Bundle;

import android.os.IBinder;

import android.os.RemoteException;

import android.util.Log;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

import android.widget.Toast;

public class RemoteClient extends Activity {

/** Called when the activity is first created. */

Button start;

IRemoteInterface serviceInterface;

Context localContext;

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

start = (Button)findViewById(R.id.startServer);

localContext = this;

start.setOnClickListener(new OnClickListener() {

@Override

public void onClick(View v) {

// TODO Auto-generated method stub

startServ();

bindServ();

}

});

}

private ServiceConnection conn = new ServiceConnection() {

@Override

public void onServiceDisconnected(ComponentName name) {

// TODO Auto-generated method stub

}

@Override

public void onServiceConnected(ComponentName name, IBinder service) {

// TODO Auto-generated method stub

Log.i("RemoteClient","In onServicen binded...");

try {

serviceInterface = IRemoteInterface.Stub.asInterface(service);

serviceInterface.setName("Zest of Android");

Log.i("RemoteClient","User Name =”+serviceInterface.getName());

Toast.makeText(localContext, ""+serviceInterface.getName(), Toast.LENGTH_SHORT).show();

} catch (RemoteException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

};

private void bindServ() {

// TODO Auto-generated method stub

startService(new Intent("com.self.RemoteServer"));

}

private void startServ() {

// TODO Auto-generated method stub

bindService(new Intent("com.self.RemoteServer") , conn, Context.BIND_AUTO_CREATE);

}

5- When we bind the service the in onServiceConnected method we type cast the IBinder in store it in one of reference of Interface. And using this object we can call the Remote service methods.

Thus we now bind our Application with remote Service.