BrowseSupportFragment

Print the Fragments's state into the given stream.

Subclasses can not override equals().

Return the FragmentActivity this fragment is currently associated with. May return null if the fragment is associated with a Context instead.

Returns whether the the exit transition and enter transition overlap or not. When true, the enter transition will start as soon as possible. When false, the enter transition will wait until the exit transition completes before starting.

Returns whether the the return transition and reenter transition overlap or not. When true, the reenter transition will start as soon as possible. When false, the reenter transition will wait until the return transition completes before starting.

Return the arguments supplied when the fragment was instantiated, if any.

Return a private FragmentManager for placing and managing Fragments inside of this Fragment.

Return the Context this fragment is currently associated with.

Returns the Transition that will be used to move Views into the initial scene. The entering Views will be those that are regular Views or ViewGroups that have ViewGroup#isTransitionGroup return true. Typical Transitions will extend android.transition.Visibility as entering is governed by changing visibility from View#INVISIBLE to View#VISIBLE.

Returns the Transition that will be used to move Views out of the scene when the fragment is removed, hidden, or detached when not popping the back stack. The exiting Views will be those that are regular Views or ViewGroups that have ViewGroup#isTransitionGroup return true. Typical Transitions will extend android.transition.Visibility as exiting is governed by changing visibility from View#VISIBLE to View#INVISIBLE. If transition is null, the views will remain unaffected.

Return the FragmentManager for interacting with fragments associated with this fragment's activity. Note that this will be non-null slightly before getActivity(), during the time from when the fragment is placed in a FragmentTransaction until it is committed and attached to its activity.

If this Fragment is a child of another Fragment, the FragmentManager returned here will be the parent's getChildFragmentManager().

Return the host object of this fragment. May return null if the fragment isn't currently being hosted.

Return the identifier this fragment is known by. This is either the android:id value supplied in a layout or the container view ID supplied when adding the fragment.

Returns the cached LayoutInflater used to inflate Views of this Fragment. If onGetLayoutInflater(Bundle) has not been called onGetLayoutInflater(Bundle) will be called with a null argument and that value will be cached.

The cached LayoutInflater will be replaced immediately prior to onCreateView(LayoutInflater, ViewGroup, Bundle) and cleared immediately after onDetach().

Returns the Lifecycle of the provider.

Overriding this method is no longer supported and this method will be made final in a future version of Fragment.

Return the LoaderManager for this fragment.

Returns the parent Fragment containing this Fragment. If this Fragment is attached directly to an Activity, returns null.

Returns the Transition that will be used to move Views in to the scene when returning due to popping a back stack. The entering Views will be those that are regular Views or ViewGroups that have ViewGroup#isTransitionGroup return true. Typical Transitions will extend android.transition.Visibility as exiting is governed by changing visibility from View#VISIBLE to View#INVISIBLE. If nothing is set, the default will be to use the same transition as getExitTransition().

Return requireActivity().getResources().

Returns the Transition that will be used to move Views out of the scene when the Fragment is preparing to be removed, hidden, or detached because of popping the back stack. The exiting Views will be those that are regular Views or ViewGroups that have ViewGroup#isTransitionGroup return true. Typical Transitions will extend android.transition.Visibility as entering is governed by changing visibility from View#VISIBLE to View#INVISIBLE. If nothing is set, the default will be to use the same transition as getEnterTransition().

Returns the Transition that will be used for shared elements transferred into the content Scene. Typical Transitions will affect size and location, such as android.transition.ChangeBounds. A null value will cause transferred shared elements to blink to the final position.

Return the Transition that will be used for shared elements transferred back during a pop of the back stack. This Transition acts in the leaving Fragment. Typical Transitions will affect size and location, such as android.transition.ChangeBounds. A null value will cause transferred shared elements to blink to the final position. If no value is set, the default will be to use the same value as setSharedElementEnterTransition(Object).

Return a localized string from the application's package's default string table.

Return a localized formatted string from the application's package's default string table, substituting the format arguments as defined in java.util.Formatter and java.lang.String#format.

Get the tag name of the fragment, if specified.

Return the target fragment set by setTargetFragment.

Return the target request code set by setTargetFragment.

Return a localized, styled CharSequence from the application's package's default string table.

Get the root view for the fragment's layout (the one returned by onCreateView), if provided.

Get a LifecycleOwner that represents the Fragment's View lifecycle. In most cases, this mirrors the lifecycle of the Fragment itself, but in cases of detached Fragments, the lifecycle of the Fragment can be considerably longer than the lifecycle of the View itself.

Namely, the lifecycle of the Fragment's View is:

1. created after onViewStateRestored(Bundle)
2. started after onStart()
3. resumed after onResume()
4. paused before onPause()
5. stopped before onStop()
6. destroyed before onDestroyView()

The view lifecycle remains valid through the call to onDestroyView(), after which getView() will return null, the view lifecycle will be destroyed, and this method will throw an IllegalStateException. Consider using getViewLifecycleOwnerLiveData() or FragmentTransaction#runOnCommit(Runnable) to receive a callback for when the Fragment's view lifecycle is available.

This should only be called on the main thread.

Overriding this method is no longer supported and this method will be made final in a future version of Fragment.

Retrieve a LiveData which allows you to observe the lifecycle of the Fragment's View.

This will be set to the new LifecycleOwner after onCreateView returns a non-null View and will set to null after onDestroyView().

Overriding this method is no longer supported and this method will be made final in a future version of Fragment.

Returns the ViewModelStore associated with this Fragment

Overriding this method is no longer supported and this method will be made final in a future version of Fragment.

Subclasses can not override hashCode().

Like instantiate(Context, String, Bundle) but with a null argument Bundle.

Create a new instance of a Fragment with the given class name. This is the same as calling its empty constructor, setting the ClassLoader on the supplied arguments, then calling setArguments(Bundle).

Return true if the fragment is currently added to its activity.

Return true if the fragment has been explicitly detached from the UI. That is, FragmentTransaction.detach(Fragment) has been used on it.

Return true if the fragment has been hidden. By default fragments are shown. You can find out about changes to this state with onHiddenChanged. Note that the hidden state is orthogonal to other states -- that is, to be visible to the user, a fragment must be both started and not hidden.

Return true if the layout is included as part of an activity view hierarchy via the <fragment> tag. This will always be true when fragments are created through the <fragment> tag, except in the case where an old fragment is restored from a previous state and it does not appear in the layout of the current state.

Return true if this fragment is currently being removed from its activity. This is not whether its activity is finishing, but rather whether it is in the process of being removed from its activity.

Return true if the fragment is in the resumed state. This is true for the duration of onResume() and onPause() as well.

Returns true if this fragment is added and its state has already been saved by its host. Any operations that would change saved state should not be performed if this method returns true, and some operations such as setArguments(Bundle) will fail.

Return true if the fragment is currently visible to the user. This means it: (1) has been added, (2) has its view attached to the window, and (3) is not hidden.

Called when the fragment's activity has been created and this fragment's view hierarchy instantiated. It can be used to do final initialization once these pieces are in place, such as retrieving views or restoring state. It is also useful for fragments that use setRetainInstance(boolean) to retain their instance, as this callback tells the fragment when it is fully associated with the new activity instance. This is called after onCreateView and before onViewStateRestored(Bundle).

Receive the result from a previous call to startActivityForResult(Intent, int). This follows the related Activity API as described there in Activity#onActivityResult(int, int, Intent).

Called when a fragment is first attached to its context. onCreate(Bundle) will be called after this.

Called when a fragment is first attached to its activity. onCreate(Bundle) will be called after this.

Called when a fragment is attached as a child of this fragment.

This is called after the attached fragment's onAttach and before the attached fragment's onCreate if the fragment has not yet had a previous call to onCreate.

This hook is called whenever an item in a context menu is selected. The default implementation simply returns false to have the normal processing happen (calling the item's Runnable or sending a message to its Handler as appropriate). You can use this method for any items for which you would like to do processing without those other facilities.

Use MenuItem#getMenuInfo() to get extra information set by the View that added this menu item.

Derived classes should call through to the base class for it to perform the default menu handling.

Called to do initial creation of a fragment. This is called after onAttach(Activity) and before onCreateView(LayoutInflater, ViewGroup, Bundle).

Note that this can be called while the fragment's activity is still in the process of being created. As such, you can not rely on things like the activity's content view hierarchy being initialized at this point. If you want to do work once the activity itself is created, see onActivityCreated(Bundle).

Any restored child fragments will be created before the base Fragment.onCreate method returns.

Called when a fragment loads an animation. Note that if FragmentTransaction#setCustomAnimations(int, int) was called with Animator resources instead of Animation resources, nextAnim will be an animator resource.

Called when a fragment loads an animator. This will be called when onCreateAnimation(int, boolean, int) returns null. Note that if FragmentTransaction#setCustomAnimations(int, int) was called with Animation resources instead of Animator resources, nextAnim will be an animation resource.

Called when a context menu for the view is about to be shown. Unlike onCreateOptionsMenu, this will be called every time the context menu is about to be shown and should be populated for the view (or item inside the view for AdapterView subclasses, this can be found in the menuInfo)).

Use onContextItemSelected(android.view.MenuItem) to know when an item has been selected.

The default implementation calls up to Activity.onCreateContextMenu, though you can not call this implementation if you don't want that behavior.

It is not safe to hold onto the context menu after this method returns.

Initialize the contents of the Fragment host's standard options menu. You should place your menu items in to menu. For this method to be called, you must have first called setHasOptionsMenu. See Activity.onCreateOptionsMenu for more information.

Called to have the fragment instantiate its user interface view. This is optional, and non-graphical fragments can return null. This will be called between onCreate(Bundle) and onActivityCreated(Bundle).

A default View can be returned by calling Fragment(int) in your constructor. Otherwise, this method returns null.

It is recommended to only inflate the layout in this method and move logic that operates on the returned View to onViewCreated(View, Bundle).

If you return a View from here, you will later be called in onDestroyView when the view is being released.

Called when the fragment is no longer in use. This is called after onStop() and before onDetach().

Called when this fragment's option menu items are no longer being included in the overall options menu. Receiving this call means that the menu needed to be rebuilt, but this fragment's items were not included in the newly built menu (its onCreateOptionsMenu(Menu, MenuInflater) was not called).

Called when the fragment is no longer attached to its activity. This is called after onDestroy().

Returns the LayoutInflater used to inflate Views of this Fragment. The default implementation will throw an exception if the Fragment is not attached.

Called when the hidden state (as returned by isHidden() of the fragment has changed. Fragments start out not hidden; this will be called whenever the fragment changes state from that.

Called when a fragment is being created as part of a view layout inflation, typically from setting the content view of an activity. This may be called immediately after the fragment is created from a tag in a layout file. Note this is before the fragment's onAttach(Activity) has been called; all you should do here is parse the attributes and save them away.

This is called every time the fragment is inflated, even if it is being inflated into a new instance with saved state. It typically makes sense to re-parse the parameters each time, to allow them to change with different configurations.

Here is a typical implementation of a fragment that can take parameters both through attributes supplied here as well from getArguments():

Note that parsing the XML attributes uses a "styleable" resource. The declaration for the styleable used here is:

The fragment can then be declared within its activity's content layout through a tag like this:

This fragment can also be created dynamically from arguments given at runtime in the arguments Bundle; here is an example of doing so at creation of the containing activity:

Called when a fragment is being created as part of a view layout inflation, typically from setting the content view of an activity.

Called when the Fragment's activity changes from fullscreen mode to multi-window mode and visa-versa. This is generally tied to Activity#onMultiWindowModeChanged of the containing Activity.

This hook is called whenever an item in your options menu is selected. The default implementation simply returns false to have the normal processing happen (calling the item's Runnable or sending a message to its Handler as appropriate). You can use this method for any items for which you would like to do processing without those other facilities.

Derived classes should call through to the base class for it to perform the default menu handling.

This hook is called whenever the options menu is being closed (either by the user canceling the menu with the back/menu button, or when an item is selected).

Called by the system when the activity changes to and from picture-in-picture mode. This is generally tied to Activity#onPictureInPictureModeChanged of the containing Activity.

Prepare the Fragment host's standard options menu to be displayed. This is called right before the menu is shown, every time it is shown. You can use this method to efficiently enable/disable items or otherwise dynamically modify the contents. See Activity.onPrepareOptionsMenu for more information.

Callback for when the primary navigation state of this Fragment has changed. This can be the result of the containing FragmentManager having its primary navigation fragment changed via androidx.fragment.app.FragmentTransaction#setPrimaryNavigationFragment or due to the primary navigation fragment changing in a parent FragmentManager.

Callback for the result from requesting permissions. This method is invoked for every call on requestPermissions(String[], int).

Note: It is possible that the permissions request interaction with the user is interrupted. In this case you will receive empty permissions and results arrays which should be treated as a cancellation.

Called when the Fragment is no longer started. This is generally tied to Activity.onStop of the containing Activity's lifecycle.

Called when all saved state has been restored into the view hierarchy of the fragment. This can be used to do initialization based on saved state that you are letting the view hierarchy track itself, such as whether check box widgets are currently checked. This is called after onActivityCreated(Bundle) and before onStart().

Postpone the entering Fragment transition until startPostponedEnterTransition() or FragmentManager#executePendingTransactions() has been called.

This method gives the Fragment the ability to delay Fragment animations until all data is loaded. Until then, the added, shown, and attached Fragments will be INVISIBLE and removed, hidden, and detached Fragments won't be have their Views removed. The transaction runs when all postponed added Fragments in the transaction have called startPostponedEnterTransition().

This method should be called before being added to the FragmentTransaction or in onCreate(Bundle), onAttach(Context), or onCreateView(LayoutInflater, ViewGroup, Bundle)}. startPostponedEnterTransition() must be called to allow the Fragment to start the transitions.

When a FragmentTransaction is started that may affect a postponed FragmentTransaction, based on which containers are in their operations, the postponed FragmentTransaction will have its start triggered. The early triggering may result in faulty or nonexistent animations in the postponed transaction. FragmentTransactions that operate only on independent containers will not interfere with each other's postponement.

Calling postponeEnterTransition on Fragments with a null View will not postpone the transition. Likewise, postponement only works if FragmentTransaction reordering is enabled.

Postpone the entering Fragment transition for a given amount of time and then call startPostponedEnterTransition().

This method gives the Fragment the ability to delay Fragment animations for a given amount of time. Until then, the added, shown, and attached Fragments will be INVISIBLE and removed, hidden, and detached Fragments won't be have their Views removed. The transaction runs when all postponed added Fragments in the transaction have called startPostponedEnterTransition().

This method should be called before being added to the FragmentTransaction or in onCreate(Bundle), onAttach(Context), or onCreateView(LayoutInflater, ViewGroup, Bundle)}.

When a FragmentTransaction is started that may affect a postponed FragmentTransaction, based on which containers are in their operations, the postponed FragmentTransaction will have its start triggered. The early triggering may result in faulty or nonexistent animations in the postponed transaction. FragmentTransactions that operate only on independent containers will not interfere with each other's postponement.

Calling postponeEnterTransition on Fragments with a null View will not postpone the transition. Likewise, postponement only works if FragmentTransaction reordering is enabled.

Registers a context menu to be shown for the given view (multiple views can show the context menu). This method will set the OnCreateContextMenuListener on the view to this fragment, so onCreateContextMenu(ContextMenu, View, ContextMenuInfo) will be called when it is time to show the context menu.

Requests permissions to be granted to this application. These permissions must be requested in your manifest, they should not be granted to your app, and they should have protection level #PROTECTION_DANGEROUS dangerous, regardless whether they are declared by the platform or a third-party app.

Normal permissions android.content.pm.PermissionInfo#PROTECTION_NORMAL are granted at install time if requested in the manifest. Signature permissions android.content.pm.PermissionInfo#PROTECTION_SIGNATURE are granted at install time if requested in the manifest and the signature of your app matches the signature of the app declaring the permissions.

If your app does not have the requested permissions the user will be presented with UI for accepting them. After the user has accepted or rejected the requested permissions you will receive a callback on reporting whether the permissions were granted or not.

Note that requesting a permission does not guarantee it will be granted and your app should be able to run without having this permission.

This method may start an activity allowing the user to choose which permissions to grant and which to reject. Hence, you should be prepared that your activity may be paused and resumed. Further, granting some permissions may require a restart of you application. In such a case, the system will recreate the activity stack before delivering the result to .

When checking whether you have a permission you should use .

Calling this API for permissions already granted to your app would show UI to the user to decided whether the app can still hold these permissions. This can be useful if the way your app uses the data guarded by the permissions changes significantly.

A sample permissions request looks like this:

<code><p> private void showContacts() { if (getActivity().checkSelfPermission(Manifest.permission.READ_CONTACTS) != PackageManager.PERMISSION_GRANTED) { requestPermissions(new String[]{Manifest.permission.READ_CONTACTS}, PERMISSIONS_REQUEST_READ_CONTACTS); } else { doShowContacts(); } } @Override public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) { if (requestCode == PERMISSIONS_REQUEST_READ_CONTACTS &amp;&amp; grantResults[0] == PackageManager.PERMISSION_GRANTED) { doShowContacts(); } } </p></code>

Return the FragmentActivity this fragment is currently associated with.

Return the arguments supplied when the fragment was instantiated.

Return the Context this fragment is currently associated with.

Return the FragmentManager for interacting with fragments associated with this fragment's activity. Note that this will available slightly before getActivity(), during the time from when the fragment is placed in a FragmentTransaction until it is committed and attached to its activity.

If this Fragment is a child of another Fragment, the FragmentManager returned here will be the parent's getChildFragmentManager().

Return the host object of this fragment.

Returns the parent Fragment containing this Fragment.

Get the root view for the fragment's layout (the one returned by onCreateView).

Sets whether the the exit transition and enter transition overlap or not. When true, the enter transition will start as soon as possible. When false, the enter transition will wait until the exit transition completes before starting.

Sets whether the the return transition and reenter transition overlap or not. When true, the reenter transition will start as soon as possible. When false, the reenter transition will wait until the return transition completes before starting.

Supply the construction arguments for this fragment. The arguments supplied here will be retained across fragment destroy and creation.

This method cannot be called if the fragment is added to a FragmentManager and if isStateSaved() would return true.

When custom transitions are used with Fragments, the enter transition callback is called when this Fragment is attached or detached when not popping the back stack.

Sets the Transition that will be used to move Views into the initial scene. The entering Views will be those that are regular Views or ViewGroups that have ViewGroup#isTransitionGroup return true. Typical Transitions will extend android.transition.Visibility as entering is governed by changing visibility from View#INVISIBLE to View#VISIBLE. If transition is null, entering Views will remain unaffected.

When custom transitions are used with Fragments, the exit transition callback is called when this Fragment is attached or detached when popping the back stack.

Sets the Transition that will be used to move Views out of the scene when the fragment is removed, hidden, or detached when not popping the back stack. The exiting Views will be those that are regular Views or ViewGroups that have ViewGroup#isTransitionGroup return true. Typical Transitions will extend android.transition.Visibility as exiting is governed by changing visibility from View#VISIBLE to View#INVISIBLE. If transition is null, the views will remain unaffected.

Report that this fragment would like to participate in populating the options menu by receiving a call to onCreateOptionsMenu and related methods.

Set the initial saved state that this Fragment should restore itself from when first being constructed, as returned by FragmentManager.saveFragmentInstanceState.

Set a hint for whether this fragment's menu should be visible. This is useful if you know that a fragment has been placed in your view hierarchy so that the user can not currently seen it, so any menu items it has should also not be shown.

Sets the Transition that will be used to move Views in to the scene when returning due to popping a back stack. The entering Views will be those that are regular Views or ViewGroups that have ViewGroup#isTransitionGroup return true. Typical Transitions will extend android.transition.Visibility as exiting is governed by changing visibility from View#VISIBLE to View#INVISIBLE. If transition is null, the views will remain unaffected. If nothing is set, the default will be to use the same transition as getExitTransition().

Control whether a fragment instance is retained across Activity re-creation (such as from a configuration change). If set, the fragment lifecycle will be slightly different when an activity is recreated:

• onDestroy() will not be called (but onDetach() still will be, because the fragment is being detached from its current activity).
• onCreate(Bundle) will not be called since the fragment is not being re-created.
• onAttach(Activity) and onActivityCreated(Bundle) will still be called.

Sets the Transition that will be used to move Views out of the scene when the Fragment is preparing to be removed, hidden, or detached because of popping the back stack. The exiting Views will be those that are regular Views or ViewGroups that have ViewGroup#isTransitionGroup return true. Typical Transitions will extend android.transition.Visibility as entering is governed by changing visibility from View#VISIBLE to View#INVISIBLE. If transition is null, entering Views will remain unaffected. If nothing is set, the default will be to use the same value as set in setEnterTransition(Object).

Sets the Transition that will be used for shared elements transferred into the content Scene. Typical Transitions will affect size and location, such as android.transition.ChangeBounds. A null value will cause transferred shared elements to blink to the final position.

Sets the Transition that will be used for shared elements transferred back during a pop of the back stack. This Transition acts in the leaving Fragment. Typical Transitions will affect size and location, such as android.transition.ChangeBounds. A null value will cause transferred shared elements to blink to the final position. If no value is set, the default will be to use the same value as setSharedElementEnterTransition(Object).

Optional target for this fragment. This may be used, for example, if this fragment is being started by another, and when done wants to give a result back to the first. The target set here is retained across instances via FragmentManager.putFragment().

Set a hint to the system about whether this fragment's UI is currently visible to the user. This hint defaults to true and is persistent across fragment instance state save and restore.

An app may set this to false to indicate that the fragment's UI is scrolled out of visibility or is otherwise not directly visible to the user. This may be used by the system to prioritize operations such as fragment lifecycle updates or loader ordering behavior.

Note: This method may be called outside of the fragment lifecycle. and thus has no ordering guarantees with regard to fragment lifecycle method calls.

Gets whether you should show UI with rationale for requesting a permission. You should do this only if you do not have the permission and the context in which the permission is requested does not clearly communicate to the user what would be the benefit from granting this permission.

For example, if you write a camera app, requesting the camera permission would be expected by the user and no rationale for why it is requested is needed. If however, the app needs location for tagging photos then a non-tech savvy user may wonder how location is related to taking photos. In this case you may choose to show UI with rationale of requesting this permission.

Call Activity#startActivity(Intent) from the fragment's containing Activity.

Call Activity#startActivity(Intent, Bundle) from the fragment's containing Activity.

Call Activity#startActivityForResult(Intent, int) from the fragment's containing Activity.

Call Activity#startActivityForResult(Intent, int, Bundle) from the fragment's containing Activity.

Call Activity#startIntentSenderForResult(IntentSender, int, Intent, int, int, int, * Bundle) from the fragment's containing Activity.

Begin postponed transitions after postponeEnterTransition() was called. If postponeEnterTransition() was called, you must call startPostponedEnterTransition() or FragmentManager#executePendingTransactions() to complete the FragmentTransaction. If postponement was interrupted with FragmentManager#executePendingTransactions(), before startPostponedEnterTransition(), animations may not run or may execute improperly.

Prevents a context menu to be shown for the given view. This method will remove the OnCreateContextMenuListener on the view.

Returns the badge drawable used in the fragment title.

Returns the color used to draw the search affordance.

Returns the androidx.leanback.widget.SearchOrbView.Colors used to draw the search affordance.

Returns the title text for the fragment.

Returns the view that implements TitleViewAdapter.Provider.

Returns the TitleViewAdapter implemented by title view.

Inflate title view and add to parent. This method should be called in Fragment#onCreateView(LayoutInflater, ViewGroup, Bundle).

Returns true/false to indicate the visibility of TitleView.

Called by installTitleView(LayoutInflater, ViewGroup, Bundle) to inflate title view. Default implementation uses layout file lb_browse_title. Subclass may override and use its own layout, the layout must have a descendant with id browse_title_group that implements TitleViewAdapter.Provider. Subclass may return null if no title is needed.

Sets the drawable displayed in the fragment title.

Sets a click listener for the search affordance.

The presence of a listener will change the visibility of the search affordance in the fragment title. When set to non-null, the title will contain an element that a user may click to begin a search.

The listener's onClick method will be invoked when the user clicks on the search element.

Sets the color used to draw the search affordance. A default brighter color will be set by the framework.

Sets the androidx.leanback.widget.SearchOrbView.Colors used to draw the search affordance.

Sets title text for the fragment.

Sets the view that implemented TitleViewAdapter.

Shows or hides the title view.

Changes title view's components visibility and shows title.

Returns the ProgressBarManager.

Enables entrance transition.

Entrance transition is the standard slide-in transition that shows rows of data in browse screen and details screen.

The method is ignored before LOLLIPOP (API21).

This method must be called in or before onCreate(). Typically entrance transition should be enabled when savedInstance is null so that fragment restored from instanceState does not run an extra entrance transition. When the entrance transition is enabled, the fragment will make headers and content hidden initially. When data of rows are ready, app must call startEntranceTransition() to kick off the transition, otherwise the rows will be invisible forever.

It is similar to android:windowsEnterTransition and can be considered a late-executed android:windowsEnterTransition controlled by app. There are two reasons that app needs it:

Transition object is returned by createEntranceTransition(). Typically the app does not need override the default transition that browse and details provides.

When fragment finishes loading data, it should call startEntranceTransition() to execute the entrance transition. startEntranceTransition() will start transition only if both two conditions are satisfied:

If startEntranceTransition() is called before onViewCreated(), it will be pending and executed when view is created.