Observe Android application’s foreground & background states with Jetpack’s Lifecycle library

Photo by Jonathan Kemper on Unsplash

Knowing when the app goes into background or for that matter knowing the lifecycle of the whole appilcation helps developers to implement various features. Developers have been trying various methods to acheive this, but none of them are well suited for every instance and has it’s own drawbacks.

With Android’s Jetpack library androidx.lifecycle it is very convenient to observer lifecycle of various android components like activities, fragments etc., With this library any class can be made to have lifecycle awareness. Libraries are segmented based on components and we can implement only those which are required in the project.

Here let’s see how to obeserve the whole application’s lifecycle.

step 1:

Implement the dependencies.

dependencies required in build.gradle

step 2:

Create a class that implements LifecycleObserver or DefaultLifecycleObserver, if using java 8.

If using java 8 override methods onCreate, onPause, onResume etc., to listen to process lifecycle events. Otherwise if java 8 is not being used create methods and annotate with @OnLifecycleEvent(Lifecycle.Event.ON_CREATE), @OnLifecycleEvent(Lifecycle.Event.ON_PAUSE) etc., to listen to the lifecycle events.

Class which responds to lifecycle calls. This can also be implemented on Application class.

Only the required method can be created or overriden.

step 3:

In the application class add the above listener to the ProcessLifecycleOwner.

Adding the observer class.

Now we can listen to all the lifecycle events related to the application.

Note: There will be a few milliseconds delay in receiving the calls as it will be called after the respective components lifecycle events are called.