1. A broadcast receiver is an Android component which allows to register and listen for device orientation changes like sms messsage recieved , phone call recieved/pick/cut ,battery status changed, the Wi-Fi came on.
2. Android operating system and even other applications time to time broadcast messages about things that are happening like sms messsage recieved , phone call recieved/pick/cut ,battery status changed, the Wi-Fi came on.
3. With the help of broadcast receiver you will catch Android operating system specific events and then you can code your application for that event.
Example:
We want when any call will come then we will save call details in our sqlite database.
How to do :
We will define a broadcast receiver which listens to telephone state changes. If the phone receives a phone call then our receiver will be notified and save call data to sqlite database.
There are two way to register and create a broadcast receiver
First Way :
Register broadcast receiver Via the AndroidManifest.xml file.
<receiver android:name="IncomingCall">
<intent-filter>
<action android:name="android.intent.action.PHONE_STATE" />
</intent-filter>
</receiver>
When android.intent.action.PHONE_STATE Event will fire ( call recieved/pick/end ), then onReceive method in IncomingCall.java file will automaticaly call.
Now Create IncomingCall.java file
// Reciever class which extends BroadcastReceiver
public class IncomingCall extends BroadcastReceiver {
public void onReceive(Context context, Intent intent) {
// Phone call state change then this method will automaticaly called
}
}
Second Way :
Register broadcast receiver Via dynamically ( Run time )
// Create reciever object
private BroadcastReceiver the_receiver = new IncomingCall();
// Set When broadcast event will fire.
private IntentFilter filter = new IntentFilter(Intent.ACTION_CONFIGURATION_CHANGED);
// Register new broadcast receiver
this.registerReceiver(the_receiver, filter);
// Reciever class which extends BroadcastReceiver
public class IncomingCall extends BroadcastReceiver {
public void onReceive(Context context, Intent intent) {
// Phone call state change then this method will automaticaly called
}
}
Define BroadcastReceiver in AndroidManifest.xml file to a Custom action.
Custom action - define any user specific name , event will broadcast with that name.
<receiver android:name="MyReceiver" >
<intent-filter>
<action android:name="ax.androidexample.mybroadcast" />
</intent-filter>
</receiver>
Create reciever class :
// Reciever class which extends BroadcastReceiver
public class MyReceiver extends BroadcastReceiver {
public void onReceive(Context context, Intent intent) {
// Phone call state change then this method will automaticaly called
}
}
Send Broadcast event :
Create new intent and broadcast it
Intent intent = new Intent();
intent.setAction("ax.androidexample.mybroadcast");
sendBroadcast(intent);
public class Android Example extends Activity {
private BroadcastReceiver the_receiver = new BroadcastReceiver(){
@Override
public void onReceive(Context c, Intent i) {
}
};
// Set When broadcast event will fire.
private IntentFilter filter = new IntentFilter(Intent.ACTION_CONFIGURATION_CHANGED);
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
@Override
protected void onResume() {
// Register reciever if activity is in front
this.registerReceiver(the_receiver, filter);
super.onResume();
}
@Override
protected void onPause() {
// Unregister reciever if activity is not in front
this.unregisterReceiver(the_receiver);
super.onPause();
}
}
After the onReceive() method completed, BroadcastReceiver has finished, the Android system can recycle the BroadcastReceiver.
So you cannot perform any asynchronous operation in the onReceive() method. If you have potentially long running operations( Request to server, get contacts etc.. ) you should call / create a service for that.
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