Activity Class

To implement an Android Activity, the class must extend the Activity class. The Activity class is a common interface for user interaction. It contains the following methods:

• onStart()

• onRestart()

• onResume()

• onPause()

• onStop()

• onDestroy()

The methods in the Activity class are part of the Activity Lifecycle and are called lifecycle methods. When these methods are overridden, various lifecycle hook methods that do necessary work when the Activity changes states are also overridden, but this makes it easier to debug and monitor the application.

Hook Methods

1. Lifecycle hook methods are a way to customize reasonable framework classes to run app-specific logic.

2. They are used because it is essential to know when an activity can be killed to avoid surprises, much like with animals, people, planets, etc.

3. The Android Manager Service has the job of calling the lifecycle hook methods back automatically and calling the lifecycle hook methods to Services and Broadcast Receivers, more on those later.

4. In any overridden hook method, the super class method is called first (super.methodName()) to see if the superclass has to do anything before we start doing something

   1. If the hook method is not overwritten in the subclass, the Android Manager Service will invoke the default activity method implementations.