Activity: it is single screen application. it is a foreground process.it contain user interaction.
Service:
a service is a component which runs in the background without interacting with user.
Android provides many predefined services exposed via Manager class.
Own services must be declared in the manifest file..
Some methods:
An activity can start a service via startService() method.
stop the service by using stopService() method.
bindService() - this is for activity to interact with service.
it needs "ServiceConnection" object.
Once service is started onCreate() is called.
onStart()
onBind()- the system calls when other component want to bind the service.
onStop() - for stopping the service.
OnDestroy()- called when service is no longer used. and it is destroyed.
ex:
MainActivity.java
package
com.example.serviceexample;
import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
public class MainActivity extends Activity
implements OnClickListener {
Button b1;
Button b2;
@Override
public void
onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
b1=(Button)findViewById(R.id.button1);
b2=(Button)findViewById(R.id.button2);
b1.setOnClickListener(this);
b2.setOnClickListener(this);
}
@Override
public boolean
onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.activity_main,
menu);
return true;
}
public void
onClick(View v) {
// TODO Auto-generated method stub
switch(v.getId())
{
case R.id.button1:
startService(new Intent(this,ServiceDemo.class));
break;
case R.id.button2:
startService(new Intent(this,ServiceDemo.class));
}
}
}
ServiceDemo.java
package com.example.serviceexample;
import android.app.Service;
import android.content.Intent;
import android.media.MediaPlayer;
import android.os.IBinder;
public class
ServiceDemo extends Service{
MediaPlayer mediaplayer;
@Override
public IBinder onBind(Intent arg0) {
// TODO Auto-generated method
stub
return null;
}
@Override
public void
onCreate() {
// TODO Auto-generated method
stub
super.onCreate();
mediaplayer=MediaPlayer.create(this,
R.raw.newsong);
}
@Override
public void
onDestroy() {
// TODO Auto-generated method
stub
super.onDestroy();
mediaplayer.stop();
}
@Override
public void
onStart(Intent intent, int
startId) {
// TODO Auto-generated method
stub
super.onStart(intent, startId);
mediaplayer.start();
}
}
Declare
manifest permission for service
Own services must be declared in manifest file.
how to declare own service:
<service android:name="your class"></service>
implementing class must extend the class " service or one of its subclasses.
Ex: AsyncTask:
using services in android allows to have app running in the background.
if u want to do a simple task run in the background, use AsyncTask.
AsyncTask class:
private class someclassname extends AsyncTask<x,y,z>
protected void onPreExecute()
{
// starting new thread i.e initilizing
protected void doInBackground()
// perform the action or do the task
protected void onPostExecute(){
// closing the process
}
BroadCast Receiver:
It class which extends BroadCastReceiver.
which is registered in the android app via manifest file.
This class can be able to recieve intents via sendBroadcast()
BroadCast Receiver defines the method onReceive(). During this method , BroadCast Receiver object will be valid.
ex:
public class PhoneReceiver extends BroadcastReciever
{
@override
public void onReceive()
{
}
}
