Let’s discuss about activity-
An Activity is an application component that provides a screen with which users can interact in order to do something, such as dial the phone, take a photo, send an email, or view a map. An application usually consists of multiple activities that are loosely bound to each other.
Now let us see what a lifecycle in Android is-
When an activity is stopped because a new activity starts, it is notified of this change in state through the activity’s lifecycle callback methods. There are several callback methods that an activity might receive, due to a change in its state—whether the system is creating it, stopping it, resuming it, or destroying it—and each callback provides you the opportunity to perform specific work that’s appropriate to that state change. For instance, when stopped, your activity should release any large objects, such as network or database connections. When the activity resumes, you can reacquire the necessary resources and resume actions that were interrupted. These state transitions are all part of the activity lifecycle.
There are 7 methods that manage the activity lifecycle in Android application:
1. onCreate() 2. onStart() 3. onResume() 4. onRestart() 5. onPause() 6. onStop() 7. onDestroy()
Called when the activity is first created. This is where you should do all of your normal static set up: create views, bind data to lists, etc. This method also provides you with a Bundle containing the activity’s previously frozen state, if there was one. Always followed by onStart().
Called when the activity is becoming visible to the user. Followed by onResume() if the activity comes to the foreground, or onStop() if it becomes hidden.
Called when the activity will start interacting with the user. At this point your activity is at the top of the activity stack, with user input going to it. Always followed by onPause().
Called after your activity has been stopped, prior to it being started again. Always followed by onStart()
Called as part of the activity lifecycle when an activity is going into the background, but has not (yet) been killed. The counterpart to onResume(). When activity B is launched in front of activity A, this callback will be invoked on A. B will not be created until A’s onPause() returns, so be sure to not do anything lengthy here.
Called when you are no longer visible to the user. You will next receive either onRestart(), onDestroy(), or nothing, depending on later user activity.
Note that this method may never be called, in low memory situations where the system does not have enough memory to keep your activity’s process running after its onPause() method is called.
The final call you receive before your activity is destroyed. This can happen either because the activity is finishing (someone called finish() on it, or because the system is temporarily destroying this instance of the activity to save space. You can distinguish between these two scenarios with the isFinishing() method.