![]() ![]() This call can occur if the host Activity has stopped, or the Activity has removed the Fragment. onDestroyView(): Called when the View previously created by onCreateView() has been detached from the Fragment.The onActivit圜reated() method is called after onCreateView() and before onViewStateRestored(). It is also useful for a Fragment that uses setRetainInstance() to retain its instance, as this callback tells the Fragment when it is fully associated with the new Activity instance. Use it to do final initialization, such as retrieving views or restoring state. onActivit圜reated(): Called when the Activity onCreate() method has returned.Use this method to check if the Activity has implemented the required listener callback for the Fragment (if a listener interface was defined in the Fragment). onAttach(): Called when a Fragment is first attached to a host Activity.onResume(): Called by the Activity to resume a Fragment that is visible to the user and actively running.The Fragment class has other useful lifecycle callbacks: ![]() If the user presses the Back button and the Fragment is returned from the back stack, the lifecycle resumes with the onCreateView() callback. ![]() The Fragment is replaced or removed, or another operation is modifying the Fragment.Ī paused Fragment is still alive (all state and member information is retained by the system), but it will be destroyed if the Activity is destroyed.The system calls this method if any of the following occurs: OnPause(): Save any data and states that need to survive beyond the destruction of the Fragment. Return null if the Fragment does not have a UI. To draw a UI for your Fragment, you must return the root View of your Fragment layout. As a result, the Fragment is visible in the Activity. The system calls this method to draw the Fragment UI for the first time. onCreateView(): Inflate the XML layout for the Fragment in this callback.Anything initialized in onCreate() is preserved if the Fragment is paused and resumed. The system calls this method when the Fragment is created. onCreate(): Initialize essential components and variables of the Fragment in this callback.Most apps should implement at least the following methods for every Fragment: Tip: For more information about the Activity lifecycle and saving state, see The Activity Lifecycle.Īs you would with Activity lifecycle methods, you can override Fragment lifecycle methods to perform important tasks when the Fragment is in certain states. You learn more about communicating between an Activity and a Fragment later in this chapter. Because data in a Fragment is usually relevant to the Activity that hosts it, your Activity code can use a callback to retrieve data from the Fragment, and then restore that data when recreating the Fragment. OnAttach(), onCreate(), onCreateView(), onActivit圜reated()įragment is added and its layout is inflated.įragment is active and ready for user interaction.įragment is paused because the Activity is paused.įragment is stopped and no longer visible.Īs with an Activity, you can save the variable assignments in a Fragment. For example, when the Activity receives onPause(), it triggers a Fragment onPause() for each Fragment in the Activity. For example, when the Activity is paused, so are all Fragments in it, and when the Activity is destroyed, so are all Fragments.Įach lifecycle callback for the Activity results in a similar callback for each Fragment, as shown in the following table. How the Activity state affects the Fragmentīecause a Fragment is always hosted by an Activity, the Fragment lifecycle is directly affected by the host Activity lifecycle. Once added, the Fragment goes through three states, as shown in the figure below: The Fragment is added by an Activity (which acts as the host of the Fragment). Within the Fragment lifecycle callback methods, you can declare how your Fragment behaves when it is in a certain state, such as active, paused, or stopped. Using a Fragment lifecycle is a lot like using an Activity lifecycle (see The Activity Lifecycle for details). This chapter describes the mechanisms for passing data and how to manage the Fragment lifecycle within an Activity. Understanding the relationship between Activity and Fragment lifecycles helps you design fragments that can save and restore variables and communicate with activities.Īn Activity that hosts a Fragment can send information to that Fragment, and receive information from that Fragment. Like an Activity, a Fragment has its own lifecycle. Communicating between a Fragment and an Activity.Using Fragment methods and the Activity context.Unit 6: Working with Architecture Components 1.2: Fragment lifecycle and communicationsĤ.3: Best practices: network, battery, compression ![]()
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