android populer

in java file:

 
public class MainActivity extends Activity {
  //Create broadcast object
    BroadcastReceiver mybroadcast = new BroadcastReceiver() {
  
  //When Event is published, onReceive method is called
  @Override
  public void onReceive(Context context, Intent intent) {
   // TODO Auto-generated method stub
       Log.i("[BroadcastReceiver]", "MyReceiver");

          if(intent.getAction().equals(Intent.ACTION_SCREEN_ON)){
              Log.i("[BroadcastReceiver]", "Screen ON");
          }
          else if(intent.getAction().equals(Intent.ACTION_SCREEN_OFF)){
              Log.i("[BroadcastReceiver]", "Screen OFF");
          }
   }};

   @Override
   public void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.activity_main);
 
       registerReceiver(mybroadcast, new IntentFilter(Intent.ACTION_SCREEN_ON));
       registerReceiver(mybroadcast, new IntentFilter(Intent.ACTION_SCREEN_OFF));
   }  
}

See Introduction for Broadcast Receiver here:

 When you need to call a broadcast (suppose here battery value) you need to register the broadcast and when the event is published it will call onReceive method which have context and particular intent as parameter.

 
public class Broadcast extends Activity {
  //Create broadcast object
    BroadcastReceiver mybroadcast = new BroadcastReceiver() {
   
 //When Event is published, onReceive method is called
    @Override
 public void onReceive(Context context, Intent intent) {
     //Get battery percentage
      int batterylevel = intent.getIntExtra("level", 0);     
     //get progressbar
      ProgressBar myprogressbar = (ProgressBar) findViewById(R.id.progressbar);
      myprogressbar.setProgress(batterylevel);
      TextView tv = (TextView) findViewById(R.id.textfield);
    //Set TextView with text
      tv.setText("Battery Level: " + Integer.toString(batterylevel) + "%");
     }
 };
 
    @Override
   public void onCreate(Bundle savedInstanceState) {
     super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_broadcast);    
      registerReceiver(mybroadcast, new IntentFilter(Intent.ACTION_BATTERY_CHANGED));
    } 
} 

The arguments of the registerReceiver() method
receiver :: The BroadcastReceiver you want to register
filter :: The IntentFilter object that specifies which event your receiver should listen to.

To learn more on event and usages click here...