2.App Components-Services/Bound Services

//activity_bingding.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="mirror.android.extendingbinder.BindingActivity" >
    <Button
        android:id = "@+id/btn_create_service"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Create service" />
</RelativeLayout>

//LocalService.class
package mirror.android.extendingbinder;

import java.util.Random;

import android.app.Service;
import android.content.Intent;
import android.os.Binder;
import android.os.IBinder;

public class LocalService extends Service {    
    
    private final IBinder mBinder = new LocalBinder();
    private final Random mGenerator = new Random();
    
    /*1.In your service, create an instance of Binder that either: 
     *     <1> contains public methods that the client can call
     *  <2> returns the current Service instance, which has public methods the client can call
     *  <3> or, returns an instance of another class hosted by the service with public methods the client can call
    */
    public class LocalBinder extends Binder{
        LocalService getService(){
            return LocalService.this;
        }
    }
     
    /*2.Return this instance of Binder from the onBind() callback method.
    */
    @Override
    public IBinder onBind(Intent intent) {
        // TODO Auto-generated method stub
        return mBinder;
    }
    
    /*The LocalBinder provides the getService() method for clients to retrieve the current instance of LocalService. 
     *This allows clients to call public methods in the service. 
     *For example, clients can call getRandomNumber() from the service.*/
    public int getRandomNumber(){
        return mGenerator.nextInt();
    }
}

//BindingActivity.class
package mirror.android.extendingbinder;

import mirror.android.extendingbinder.LocalService.LocalBinder;
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.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;


public class BindingActivity extends Activity {
    
    private Button button;
    
    LocalService mService;
    Boolean mBound = false;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_binding);
        
        button = (Button)findViewById(R.id.btn_create_service);
        ButtonListener buttonListener = new ButtonListener();
        button.setOnClickListener(buttonListener);
    }

    @Override
    protected void onStart() {
        super.onStart();
        //1.bind to LocalService
        Intent intent = new Intent(this, LocalService.class);
        bindService(intent, mConnection, Context.BIND_AUTO_CREATE);
    }

    @Override
    protected void onPause() {
        super.onPause();
    }

    @Override
    protected void onStop() {
        super.onStop();
        //2.unbind from service
        if(mBound){
            unbindService(mConnection);
            mBound = false;
        }
    }
    
    class ButtonListener implements OnClickListener{
        //3.Call a method from the LocalService.
        //create a separate thread if needed;
        @Override
        public void onClick(View v) {
            if(mBound){
                int num = mService.getRandomNumber();
                Toast.makeText(getApplicationContext(), "number: " + num, Toast.LENGTH_SHORT).show();
            }
        }
    }
    
    private ServiceConnection mConnection = new ServiceConnection() {
        //3.In the client, receive the Binder from the onServiceConnected() callback method 
        //  and make calls to the bound service using the methods provided.
        @Override
        public void onServiceDisconnected(ComponentName name) {
            mBound = false;
        }
        
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            LocalBinder binder = (LocalBinder)service;
            mService = binder.getService();
            mBound = true;
        }
    };
}

//manifest.xml
<application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".BindingActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <service android:name=".LocalService"></service>
    </application>