Ordered Broadcasts

There are two types of broadcasts in Android: normal and ordered. The following table shows the main differences:

	Normal	Ordered
Way of delivery	Normal broadcasts are delivered to the available receivers asynchronously, in an unspecified order	Ordered broadcasts are delivered to the available receivers one at a time, in a specified order (the order depends on the android:priority attribute of the different receivers in the AndroidManifest file)
Feedback	With normal broadcasts no feedback can be sent to the broadcaster	With ordered broadcasts the receiver can send information to the broadcaster (using the methods abortBroadcast(), seResultCode(), setResultData()

Tip: in a receiver (handling ordered broadcasts) you can call the method abortBroadcast() to make sure that the broadcast is not sent to other receivers. If you combine this method with a high value for the android:priority attribute, you can make sure that your receiver is the only one to handle that broadcast (SMS apps can use this technique).

BroadcastReceiver in Android

BroadcastReceiver

Let’s see how a BroadcastReceiver can handle ordered broadcasts (se the comments in the code for more information):

public class MyReceiver extends BroadcastReceiver {
    [...]
    public void onReceive(Context context, Intent intent) {
        //is this an ordered broadcast or not?
        if(isOrderedBroadcast() {
            //here you can handle the broadcast    
            [...]

            //here you can send information back to the broadcaster
            setResultCode(Activity.RESULT_OK);
            setResultData(“here you can pass a String”);

            //you can also create complex data to send to the broadcaster
            Bundle myBundle = getResultExtras(true);
            myBundle.put [...] //code omitted for brevity
        }
    }
}

Broadcaster

Sending an ordered broadcast is quite simple. Let’s look at the code:

Intent int = new Intent(YOUR_FILTER);
sendOrderedBroadcast(int, responseReceiver, null, RESULT_OK, null, null);

As you can see you just have to create an Intent with the filter registered for the BroadcastReceiver MyReceiver and call the method sendOrderedBroadcast. This method takes a BroadcastReceiver (responseReceiver) as a parameter: this is the receiver that will receive the information sent back by the BroadcastReceiver MyReceiver.

So you finally have to register the BroadcastReceiver responseReceiver (to handle the results) in the following way:

BroadcastReceiver responseReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        //here you can retrieve the results sent by MyReceiver
        String str = getResultData();

        //here you can retrieve the complex data sent by MyReceiver
        Bundle myBundle = getResultExtras(false);
        if(myBundle != null) {
            //here you can retrieve the data using myBundle.get... methods
        }
    }
}