Hence, the recipe for the activity-or-Notification pattern is:
Define an action string you will use when the event occurs that you want to go to the activity or notification (e.g., com.commonsware.java.packages.are.fun.EVENT).
Dynamically register a BroadcastReceiever in your activity, with an IntentFilter set up for the aforementioned action string and with a positive priority (the default priority for a filter is 0). This receiver should then have the activity do whatever it needs to do to update the UI based on this event. The receiver should also call abortBroadcast() to prevent others from getting it. Be sure to register the receiver in onStart() or onResume() and unregister the receiver in the corresponding onStop or onPause() method.
Register in your manifest a BroadcastReceiver, with an <intent-filter> set up for the aforementioned action string. This receiver should raise the Notification.
In your service (e.g., an IntentService), when the event occurs, call sendOrderedBroadcast().
And that’s it. If the activity is on-screen, its receiver will be registered, so it will get the event, process it, and cancel the broadcast. If the activity is not on-screen, its receiver will not be registered, so the event will go to the default handler, in the form of your manifest-registered BroadcastReceiver, which will raise the Notification.
Kiran Kuppa on 22 Jun 14"We are building a community-written web site which has also been used to create an O'Reilly Cookbook, both about how to build great Android applications. It is full of how-to information along with code snippets that illustrate the ideas presented. It features both how-to's that overlap with the official documentation, and material that goes beyond this to be more tutorial, more in-depth, or explaining "lessons from the trenches": what actually works to get the application functioning well. Unlike most books written by one, two or a few individuals, this one has input from dozens of contributors, who were all able to view and comment on each others' recipes before the book was published. The published version(s) include printed books, eBooks, and other uses"
