Question

Consider the apps that large blogs have (which work pretty much like an RSS feed but for your phone). Whenever the blog publishes a new post the app creates a notification on the user’s phone about the new post.

Here’s are some things I would like to understand about those:

1. Is that notification being pulled by the app on my phone or being pushed to it by the blog?
2. How come this works even if I have not launched the app?
3. What classes and services of the Android platform are used to create such apps?

Thanks a lot.

Answer 1

You could easily do something like this by:

1. Have you app set an alarm using AlarmManager
2. Have the receiver for the alarm start a Service that checks for updates
3. Display the notification to the user using the NotificationManager

That is a polling solution, which should be fine and probably better in most circumstances like you described.

However, if you want a push solution, you can look into Android C2DM which allows your server to send push notifications to a registered Android device.

Edit

How do apps run ‘without being launched’?

Well there’s a few ways. One is that any app can register for different device events; one of those is a boot-complete event.

The second way is using the AlarmManager. If an app has set an alarm then the user navigates away from the app and then the OS decides to close the app, the alarm can still be registered to run at a certain time. When this alarm is triggered will run whatever code the app developer likes, including starting a Service. Of course doing this without notifying the user can be an issue, especially if the service drains battery, etc.