Creating your own lifecycle-aware component

We need to make our CustomCountdown aware of the lifecycle of MainActivity. In other words, our countdown logic should observe and react to the lifecycle events of our LifecycleOwner – that is, MainActivity.

To make our CustomCountdown lifecycle-aware, we must force it to implement the DefaultLifecycleObserver interface. By doing so, the CustomCountdown will be observing the lifecycle events or states defined by the Lifecycle object that LifecycleOwner provides.

Our main goal is to pause the countdown when the app is put in the background and to resume it when the app is brought back into the foreground. More precisely, our CustomCountdown must react to the following lifecycle events of MainActivity:

• onPause(): When the onPause() callback comes in MainActivity, CustomCountdown must pause its countdown.
• onResume(): When the onResume() callback comes in MainActivity, CustomCountdown must resume its countdown.

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