What is Service in Android?

Service

A service is an Android application component that run in background and has no visual UI. While the user is working on the foreground UI, services can be used to handle the processes that need to be done in the background. A service can be started by another Android application components such as an activity or other services and it will continue to run in the background even after the user switches to another application. Thus services are less likely to be destroyed by Android system to free resources, than Activities.

Ex:
example of service in android that plays an audio in the background. Audio will not be stopped even if you switch to another activity. To stop the audio, you need to stop the service.

Type of Service:
2 types

1. Started(Unbound)
2. Bound

1) Started Service

Its a type of service which is not bounded to any components. Once started, it will run in the background even after the component that started the service gets killed. It can be run in the background indefinitely and should stop by itself after the operation its intended to carry out is completed.

A service is started when component (like activity) calls startService() method, now it runs in the background indefinitely. It is stopped by stopService() method. The service can stop itself by calling the stopSelf() method.

2) Bound Service

A service is bound when another component (e.g. client) calls bindService() method. The client can unbind the service by calling the unbindService() method.

The service cannot be stopped until all clients unbind the service.

Ex: Playing an Music

Step 1: activity_main.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:orientation="vertical"  android:background="#FFFFFF" >

    <Button

        android:id="@+id/buttonStart"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_marginTop="19dp"

        android:text="Start Service" />

    <Button

        android:id="@+id/buttonStop"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_marginBottom="35dp"

        android:text="Stop Service" />

    <Button

        android:id="@+id/buttonNext"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="Next Page" />

    

</LinearLayout>

Step 2: activity_next.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:orientation="vertical"   android:background="#FFFFFF"  >

    

  <TextView  

        android:id="@+id/textView1"  

        android:layout_width="wrap_content"  

        android:layout_height="wrap_content"  

        android:layout_alignParentLeft="true"  

        android:layout_alignParentTop="true"  

        android:layout_marginLeft="96dp"  

        android:layout_marginTop="112dp"     android:textColor="#000000" 

        android:text="Next Page" />  

    

    

    

</LinearLayout>

Step 3:  MainActivity.java

package com.example.servicesex;

import android.app.Activity;

import android.content.Intent;

import android.os.Bundle;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

public class MainActivity extends Activity implements OnClickListener {

Button buttonStart, buttonStop,buttonNext;  

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        buttonStart = (Button) findViewById(R.id.buttonStart);  

        buttonStop = (Button) findViewById(R.id.buttonStop);  

        buttonNext = (Button) findViewById(R.id.buttonNext);  

    

        buttonStart.setOnClickListener(this);   

        buttonStop.setOnClickListener(this);  

        buttonNext.setOnClickListener(this);  

    }

public void onClick(View v)

{

switch (v.getId())

{

 case R.id.buttonStart:

   startService(new Intent(getApplicationContext(), MyService.class));

   break;

   

 case R.id.buttonStop:

   stopService(new Intent(getApplicationContext(),MyService.class));

   break;

   

 case R.id.buttonNext:

  Intent intent=new Intent(this,NextPage.class);  

      startActivity(intent);  

      break;

}

}

}

Step 4:   MyService.java

package com.example.servicesex;

import android.app.Service;

import android.content.Intent;

import android.media.MediaPlayer;

import android.os.IBinder;

import android.widget.Toast;

public class MyService extends Service{

MediaPlayer mPlayer;

@Override

public IBinder onBind(Intent intent)

{

// TODO Auto-generated method stub

Toast.makeText(getApplicationContext(), "onBind...", 2000).show();

return null;

}

@Override

public void onCreate() {

// TODO Auto-generated method stub 

super.onCreate();

Toast.makeText(getApplicationContext(), "oncreate", 2000).show();

mPlayer=MediaPlayer.create(this,R.raw.tuhimerishab);

mPlayer.setLooping(false); 

mPlayer.start();

}

@Override

public void onStart(Intent intent, int startId) {

// TODO Auto-generated method stub

super.onStart(intent, startId);

Toast.makeText(getApplicationContext(), "onStart", 2000).show();

//mPlayer.start();

}

@Override

public void onDestroy() {

// TODO Auto-generated method stub

super.onDestroy();

System.out.println("ondestoryee"); 

Toast.makeText(getApplicationContext(), "onDestroy", 2000).show();

mPlayer.stop();

}

}

Step 5: NextStep.java

package com.example.servicesex;

import android.app.Activity;

import android.os.Bundle;

public class NextPage extends Activity

{

    @Override

protected void onCreate(Bundle savedInstanceState) 

    {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_next); 

}

}

Step 6:  Add service tag in AndroidManifest.java

 <service android:name=".MyService" android:enabled="true"></service>

        <activity android:name=".NextPage"/>