This is particularly useful when inheriting the onCreateView() implementation but we need to configure the resulting views, such as with a ListFragment and when to set up an adapter onViewCreated() : This will be called after onCreateView().We can return null if the fragment does not provide a UI To draw a UI for the fragment, a View component must be returned from this method which is the root of the fragment’s layout. onCreateView() : The system calls this callback when it’s time for the fragment to draw its UI for the first time.You are passed the Activity that will host your fragment onAttach() :This method will be called first, even before onCreate(), letting us know that your fragment has been attached to an activity.Fragment LifecycleĪndroid fragment lifecycle is illustrated in below image.īelow are the methods of fragment lifecycle. The view is then inserted into the ViewGroup parent, and the fragment is alive. The fragment then creates its view and returns it to the activity. Then it gets a reference to the ViewGroup the fragment’s view will be rendered inside. The following diagram shows depicts what happens when a fragment is added to an activity:įirst the activity obtains a reference to the fragment. The fragment’s view is displayed inside this ViewGroup. A fragment is added to a ViewGroup inside the activity.
#Fragment lifecycle android
It is this view which is eventually displayed inside the activity in which the fragment lives.īecause an android fragment is not a view, adding it to an activity looks somewhat different than adding a view (e.g. Instead, a fragment has a view inside it. A activity can contain any number of fragments.Īn Android fragment is not by itself a subclass of View which most other UI components are. A greatest advantage of fragments is that it simplifies the task of creating UI for multiple screen sizes. Fragment should be used within the Activity. Note : If you add Debug statements to Fragment2’s LifeCycle methods, you will notice that Fragment2’s onCreate(), onCreateView(), onViewCreated(), onStart() and onResume() methods are called before the above appears in the Logcat.Īs you can see the ViewModel still does not get Destroyed and if you navigate back to the first fragment using the back button then you will see that any data stored in the ViewModel is preserved and the onCreate() method is not called as the fragment was never destroyed.Fragment class in Android is used to build dynamic User Interfaces. You will notice the following in your Logcat :įragment LifeCycle: onDestroyView Called! Note : You will need to setup Navigation Component to navigate between fragments.
#Fragment lifecycle code
Now rotate your mobile or emulator, you will not see the “viewModel Destroyed” entry in your Logcat, this is because the ViewModel does not get destroyed on configuration changes and thus can be used to store data.īut does the ViewModel get destroyed if we navigate to another fragment and what about the fragment itself? Let’s try it out!Īdd another button to your layout and in its ClickListener add the following code : Now when you start your app you will also notice : Add the following methods in your ViewModel : Now if you click outside the dialogue you will notice :īut what happens to the ViewModel during all this? Well let’s experiment with that as well. When you click this button you will notice in your Logcat : This is just an implicit intent to send some data to someone else. To test this just add a button to your fragment layout and on its Click Listener write the following code : Implicit Intent That makes things a little clearer, but are onPause() and onResume() only called with other methods? No, onPause() is called when the app loses focus and OnResume() is called when it is in focus. Now if you minimize your app you will notice :Īnd if you open it again you will notice : When you open your fragment you will notice these in your Logcat :įragment LifeCycle: onViewCreated Called! So open your fragment and override the above methods like this : Now that we know what the LifeCycle looks like, let’s understand it. In activities we use the onCreate() Method to inflate the layout and bind views while in case of fragments the layout is inflated in onCreateView() Method and we bind views in the onViewCreated() method. What’s the difference then? Well, a major one would be : Fragments have similar lifecycles to Activities. If you are thinking “ That looks like the Activity LifeCycle! ”, then yes you are right. It looks something like this : Fragment LifeCycle But have you heard about the Fragment LifeCycle? If you have experimented with making an app, chances are you have probably used Fragments.
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