Sending and receiving broadcast message in Android

Sending and receiving broadcast messages enables inter activity communication. Suppose in activity A you have completed a task and you want activity B to react accordingly, then broadcasting helps a lot. A only needs to initialize an intent and send it via
a broadcast message. B needs to set a filter to get the specific messages from A and register a receiver, where the actions upon receving messages are defined.

In activity A, the message can be sent this way

Intent broadcastI=new Intent();
broadcastI.setAction("edu.hkust.cse.phoneAdapter.ruleChange");
sendBroadcast(broadcastI);

In activity B, the filter and receiver

IntentFilter filter=new IntentFilter("edu.hkust.cse.phoneAdapter.ruleChange");
this.registerReceiver(new BroadcastReceiver() {
@Override
public void onReceive(Context arg0, Intent arg1) {
Toast.makeText(getApplicationContext(), "msg received", Toast.LENGTH_SHORT).show();
}
},filter);

Easy, right?