Broadcast Reciever in Android

Broadcast  Reciever

A broadcast receiver listens for relevant broadcast messages to trigger an event. Some
examples of broadcasted events already sent from the OS are

Battrey Low
SMS Recieved
Boot Completed   etc

Type of Broadcasts: 

• Normal broadcasts are completely asynchronous. All receivers of the broadcast are run in an undefined order, often at the same time.
• Ordered broadcasts are delivered to one receiver at a time. As each receiver executes in turn, it can propagate a result to the next receiver, or it can completely abort the broadcast so that it won't be passed to other receivers. The order receivers run in can be controlled with the android:priority attribute of the matching intent-filter; receivers with the same priority will be run in an arbitrary order. 

Registering Broadcast Receivers in  Manifest  file

All Broadcast Receivers must be registered in Android Manifest file.

here I will discuss about two Broadcast

BOOT_COMPLETED   :  is delivered when device finish Booting process  
SMS_RECEIVED      :   is delivered when da new SMS is Recieved.

BOOT_COMPLETED

 <receiver android:name=".BootReceiver">
                        <intent-filter>
                                <action android:name="android.intent.action.BOOT_COMPLETED" />
                                <category android:name="android.intent.category.HOME" />
                        </intent-filter>
   </receiver>

SMS_RECEIVED

 <receiver android:name=".SMSReciever">
            <intent-filter  android:priority="1000">
                <action android:name="android.provider.Telephony.SMS_RECEIVED" />
              
            </intent-filter>
 </receiver>


We  also need to declare following permission  in manifest  to Receive these Broadcasts

    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>
    <uses-permission android:name="android.permission.RECEIVE_SMS"/>


Now we need to create  Java class to handle these events.
For this we need to Extend  BroadcastReceiver    class and override   onReceive()  method.

inside onReceive() method we write the code to handle the events  like  when a new SMS received or Device  finish Booting Process.

BroadcastReceiver Example:

In this example we have cerated a BroadcastReceiver which will receive the SMS

first we Implement SMSReciever class
in this , we will extract the Message Body and the Senders Contact Number from received SMS

here variable  messageReceived will contain the message body.

BroadCastReceiver Class

public class SmsReceiver extends BroadcastReceiver
{
    @Override
    public void onReceive(Context context, Intent intent) 
    {
        //---get the SMS message passed in---
        Bundle bundle = intent.getExtras();        
        SmsMessage[] msgs = null;
        String messageReceived = "";            
        if (bundle != null)
        {
            //---retrieve the SMS message received---
           Object[] pdus = (Object[]) bundle.get("pdus");
            msgs = new SmsMessage[pdus.length];            
            for (int i=0; i<msgs.length; i++){
                msgs[i] = SmsMessage.createFromPdu((byte[])pdus[i]);                
                messageReceived += msgs[i].getMessageBody().toString();
                messageReceived += "\n";        
            }
            //---display the new SMS message---
            Toast.makeText(context, messageReceived, Toast.LENGTH_SHORT).show();
        }                         
    }
}
  

To get the Sender's Number use 
msgs.getOriginatingAddress ()     
 
 
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