![]() ![]() Single Activity: Why, when, and how (Android Dev Summit '18).Navigate between fragments using animations.Next stepsįor more documentation and resources related to fragments, see the following. The logic necessary to manage its own UI. With this in mind, only provide a fragment with Same activity, in multiple activities, or even as a child of anotherįragment. You can use multiple instances of the same fragment class within the Of these changes in a back stack that is managed by the activity, so that Higher, fragments can be added, replaced, or removed. While your activity is in the STARTED lifecycle state or That is controlled by the activity and a linear list that is controlledĭividing your UI into fragments makes it easier to modify your activity'sĪppearance at runtime. On the right, a small screen contains a bottom navigation bar That is controlled by the activity and a grid list that is controlled by On the left, a large screen contains a navigation drawer Two versions of the same screen on different The correct navigation UI, while the fragment displays the list with the proper The activity is then responsible for displaying Separating the navigation elements from the content can make this Managing these variations in the activity is Navigation bar and a list in a linear layout. On smaller screens, you might want the app to display a bottom Might want the app to display a static navigation drawer and a list in a grid Manage the UI of a single screen or portion of a screen.Ĭonsider an app that responds to various screen sizes. Conversely, fragments are better suited to define and Place to put global elements around your app's user interface, such as a Letting you divide the UI into discrete chunks. Note: Some Android Jetpack libraries, such asįragments introduce modularity and reusability into your activity’s UI by The fragment’s view hierarchy becomes part of, or attaches to, They must be hosted by an activity or anotherįragment. Layout, has its own lifecycle, and can handle its own input events. 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.Reusable portion of your app's UI. You will notice the following in your Logcat :įragment LifeCycle: onDestroyView Called! Note : You will need to setup Navigation Component to navigate between fragments. 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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