Android life cycle components android#

The callback is immediately followed by the onStart() and onResumed() callbacks. This method is only called when the user navigates back to the stopped activity. The onRestart() function is called when the application comes back to the foreground from the background. The activity either comes back to interact with the user after running the onRestart() or finishes by executing the onDestroy() callback. In this state, the resources must be managed or released as the activity is no longer visible to the user. This may happen for the following reasons, the user performing some action that invoked another activity to come to the foreground or the activity finished. In this state, the activity is no longer visible to the user. The onStop() function is called when the application enters the stopped state. The application will not reside in this state for too long, so heavy load tasks shouldn’t be performed in this state. Use this callback to handle things that should pause/stop when the activity is in a paused state. The callback is called as a result of activity going to the background(activity still may be visible to the user in multi-screen mode). The onPause() function is called when the application enters the paused state by any action on the activity when it is in the resumed state. Here, we should get the components that are released in the paused state. The callback is called once the activity comes to a resumed state from a paused state. For example, users switching to another application or user receiving a phone call. The activity stays in the same state until some action is performed on it. In this state, the user interacts with the application. The onResume() function is called when the application enters the resumed state and comes to the foreground. Once the callback completes executing its task, it will move to the resumed state. The activity will not stay in the started state for too long. In this state, the activity comes to the foreground and becomes visible to the user. This function is called immediately after executing the onCreate() function. The onStart() function is called when the application enters the started state. If the activity never existed before, it simply returns a null. The function also has a parameter savedInstanceState, a Bundle object which contains the previous state of the activity. The callback function is required as the basic setup for the application is done in the created state like, associate the activity with the ViewModel or to bind data to the UI, etc. The callback gets triggered as the activity enters the created state. This is a callback function that should be implemented. Let’s learn what these callback functions are in detail: onCreate(): The figure below shows the detailed flow of the callbacks called when the user is interacting with the application. But it’s important to understand what they are used for, to ensure that the app works the way we want it to.

It is not necessary that we implement all the callbacks. Override the functions to achieve the required functionality when the activity’s state is being changed.

The activity has some predefined functions to handle the state changes in the application’s activity. As a user navigates through the app, the activity in the app goes through different stages in their life cycle. Users interact with the screen to perform their tasks. It’s a single screen in android, which should be inherited by the classes which have UI.

Android life cycle components android#

So, what is an Activity? Well, Activity is just a java class in android with some predefined methods which are triggered at different app states. In this blog, I will explain the concept and importance of the activity lifecycle. I started with Activity and understood that it is possible because of the Android Activity lifecycle. Well, everyone has their doubts until they learn. Before I learned Android, I had doubts about how mobile applications work and maintain their state when some interruption occurs.