Overview
NavHostFragment provides an area within your layout for self-contained navigation to occur.
NavHostFragment is intended to be used as the content area within a layout resource
defining your app's chrome around it, e.g.:
<androidx.drawerlayout.widget.DrawerLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent">
<fragment
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/my_nav_host_fragment"
android:name="androidx.navigation.fragment.NavHostFragment"
app:navGraph="@navigation/nav_sample"
app:defaultNavHost="true" />
<android.support.design.widget.NavigationView
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_gravity="start"/>
</androidx.drawerlayout.widget.DrawerLayout>
Each NavHostFragment has a NavController that defines valid navigation within
the navigation host. This includes the navigation graph as well as navigation
state such as current location and back stack that will be saved and restored along with the
NavHostFragment itself.
NavHostFragments register their navigation controller at the root of their view subtree
such that any descendant can obtain the controller instance through the Navigation
helper class's methods such as Navigation.findNavController(View). View event listener
implementations such as within navigation destination
fragments can use these helpers to navigate based on user interaction without creating a tight
coupling to the navigation host.
Summary
Methods |
---|
public static NavHostFragment | create(int graphResId)
Create a new NavHostFragment instance with an inflated NavGraph resource. |
public static NavHostFragment | create(int graphResId, Bundle startDestinationArgs)
Create a new NavHostFragment instance with an inflated NavGraph resource. |
protected Navigator<FragmentNavigator.Destination> | createFragmentNavigator()
Create the FragmentNavigator that this NavHostFragment will use. |
public static NavController | findNavController(Fragment fragment)
Find a NavController given a local Fragment. |
public final NavController | getNavController()
Returns the navigation controller for this navigation host. |
public void | onAttach(Activity activity)
Called when a fragment is first attached to its activity. |
public void | onAttachFragment(Fragment childFragment)
Called when a fragment is attached as a child of this fragment. |
public void | onCreate(Bundle savedInstanceState)
Called to do initial creation of a fragment. |
protected void | onCreateNavController(NavController navController)
Callback for when the NavController is created. |
public View | onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
Called to have the fragment instantiate its user interface view. |
public void | onDestroyView()
Called when the view previously created by Fragment.onCreateView(LayoutInflater, ViewGroup, Bundle) has
been detached from the fragment. |
public void | onInflate(Activity activity, AttributeSet attrs, Bundle savedInstanceState)
Called when a fragment is being created as part of a view layout
inflation, typically from setting the content view of an activity. |
public void | onPrimaryNavigationFragmentChanged(boolean isPrimaryNavigationFragment)
Callback for when the primary navigation state of this Fragment has changed. |
public void | onSaveInstanceState(Bundle outState)
Called to ask the fragment to save its current dynamic state, so it
can later be reconstructed in a new instance if its process is
restarted. |
public void | onViewCreated(View view, Bundle savedInstanceState)
Called immediately after Fragment.onCreateView(LayoutInflater, ViewGroup, Bundle)
has returned, but before any saved state has been restored in to the view. |
from Fragment | dump, equals, getActivity, getAllowEnterTransitionOverlap, getAllowReturnTransitionOverlap, getArguments, getChildFragmentManager, getContext, getDefaultViewModelCreationExtras, getDefaultViewModelProviderFactory, getEnterTransition, getExitTransition, getFragmentManager, getHost, getId, getLayoutInflater, getLayoutInflater, getLifecycle, getLoaderManager, getParentFragment, getParentFragmentManager, getReenterTransition, getResources, getRetainInstance, getReturnTransition, getSavedStateRegistry, getSharedElementEnterTransition, getSharedElementReturnTransition, getString, getString, getTag, getTargetFragment, getTargetRequestCode, getText, getUserVisibleHint, getView, getViewLifecycleOwner, getViewLifecycleOwnerLiveData, getViewModelStore, hashCode, hasOptionsMenu, instantiate, instantiate, isAdded, isDetached, isHidden, isInLayout, isMenuVisible, isRemoving, isResumed, isStateSaved, isVisible, onActivityCreated, onActivityResult, onAttach, onConfigurationChanged, onContextItemSelected, onCreateAnimation, onCreateAnimator, onCreateContextMenu, onCreateOptionsMenu, onDestroy, onDestroyOptionsMenu, onDetach, onGetLayoutInflater, onHiddenChanged, onInflate, onLowMemory, onMultiWindowModeChanged, onOptionsItemSelected, onOptionsMenuClosed, onPause, onPictureInPictureModeChanged, onPrepareOptionsMenu, onRequestPermissionsResult, onResume, onStart, onStop, onViewStateRestored, postponeEnterTransition, postponeEnterTransition, registerForActivityResult, registerForActivityResult, registerForContextMenu, requestPermissions, requireActivity, requireArguments, requireContext, requireFragmentManager, requireHost, requireParentFragment, requireView, setAllowEnterTransitionOverlap, setAllowReturnTransitionOverlap, setArguments, setEnterSharedElementCallback, setEnterTransition, setExitSharedElementCallback, setExitTransition, setHasOptionsMenu, setInitialSavedState, setMenuVisibility, setReenterTransition, setRetainInstance, setReturnTransition, setSharedElementEnterTransition, setSharedElementReturnTransition, setTargetFragment, setUserVisibleHint, shouldShowRequestPermissionRationale, startActivity, startActivity, startActivityForResult, startActivityForResult, startIntentSenderForResult, startPostponedEnterTransition, toString, unregisterForContextMenu |
from java.lang.Object | clone, finalize, getClass, notify, notifyAll, wait, wait, wait |
Constructors
Methods
Find a NavController given a local Fragment.
This method will locate the NavController associated with this Fragment,
looking first for a NavHostFragment along the given Fragment's parent chain.
If a NavController is not found, this method will look for one along this
Fragment's view hierarchy as specified by
Navigation.findNavController(View).
Parameters:
fragment: the locally scoped Fragment for navigation
Returns:
the locally scoped NavController for navigating from this Fragment
Create a new NavHostFragment instance with an inflated NavGraph resource.
Parameters:
graphResId: resource id of the navigation graph to inflate
Returns:
a new NavHostFragment instance
public static
NavHostFragment create(int graphResId, Bundle startDestinationArgs)
Create a new NavHostFragment instance with an inflated NavGraph resource.
Parameters:
graphResId: resource id of the navigation graph to inflate
startDestinationArgs: arguments to send to the start destination of the graph
Returns:
a new NavHostFragment instance
Returns the navigation controller for this navigation host.
This method will return null until this host fragment's NavHostFragment.onCreate(Bundle)
has been called and it has had an opportunity to restore from a previous instance state.
Returns:
this host's navigation controller
public void
onAttach(Activity activity)
Deprecated: See Fragment.onAttach(Context).
Called when a fragment is first attached to its activity.
Fragment.onCreate(Bundle) will be called after this.
public void
onCreate(Bundle savedInstanceState)
Called to do initial creation of a fragment. This is called after
Fragment.onAttach(Activity) and before
Fragment.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, add a LifecycleObserver on the
activity's Lifecycle, removing it when it receives the
callback.
Any restored child fragments will be created before the base
Fragment.onCreate
method returns.
Parameters:
savedInstanceState: If the fragment is being re-created from
a previous saved state, this is the state.
protected void
onCreateNavController(
NavController navController)
Callback for when the NavController is created. If you
support any custom destination types, their Navigator should be added here to
ensure it is available before the navigation graph is inflated / set.
By default, this adds a FragmentNavigator.
This is only called once in NavHostFragment.onCreate(Bundle) and should not be called directly by
subclasses.
Parameters:
navController: The newly created NavController.
public void
onAttachFragment(
Fragment childFragment)
Deprecated: The responsibility for listening for fragments being attached has been moved
to FragmentManager. You can add a listener to
Fragment.getChildFragmentManager() the child FragmentManager} by calling
FragmentManager.addFragmentOnAttachListener(FragmentOnAttachListener)
in Fragment.onAttach(Context) to get callbacks when a child fragment is attached.
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
.
Parameters:
childFragment: child fragment being attached
public void
onPrimaryNavigationFragmentChanged(boolean isPrimaryNavigationFragment)
Callback for when the primary navigation state of this Fragment has changed. This can be
the result of the Fragment.getParentFragmentManager() containing FragmentManager} having its
primary navigation fragment changed via
FragmentTransaction.setPrimaryNavigationFragment(Fragment) or due to
the primary navigation fragment changing in a parent FragmentManager.
Parameters:
isPrimaryNavigationFragment: True if and only if this Fragment and any
parent fragment is set as the primary navigation fragment
via FragmentTransaction.setPrimaryNavigationFragment(Fragment).
protected
Navigator<FragmentNavigator.Destination>
createFragmentNavigator()
Deprecated: Use NavHostFragment.onCreateNavController(NavController)
Create the FragmentNavigator that this NavHostFragment will use. By default, this uses
FragmentNavigator, which replaces the entire contents of the NavHostFragment.
This is only called once in NavHostFragment.onCreate(Bundle) and should not be called directly by
subclasses.
Returns:
a new instance of a FragmentNavigator
public View
onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
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
Fragment.onCreate(Bundle) and Fragment.onViewCreated(View, Bundle).
A default View can be returned by calling Fragment.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 Fragment.onViewCreated(View, Bundle).
If you return a View from here, you will later be called in
Fragment.onDestroyView() when the view is being released.
Parameters:
inflater: The LayoutInflater object that can be used to inflate
any views in the fragment,
container: If non-null, this is the parent view that the fragment's
UI should be attached to. The fragment should not add the view itself,
but this can be used to generate the LayoutParams of the view.
savedInstanceState: If non-null, this fragment is being re-constructed
from a previous saved state as given here.
Returns:
Return the View for the fragment's UI, or null.
public void
onViewCreated(View view, Bundle savedInstanceState)
Called immediately after Fragment.onCreateView(LayoutInflater, ViewGroup, Bundle)
has returned, but before any saved state has been restored in to the view.
This gives subclasses a chance to initialize themselves once
they know their view hierarchy has been completely created. The fragment's
view hierarchy is not however attached to its parent at this point.
Parameters:
view: The View returned by Fragment.onCreateView(LayoutInflater, ViewGroup, Bundle).
savedInstanceState: If non-null, this fragment is being re-constructed
from a previous saved state as given here.
public void
onInflate(Activity activity, AttributeSet attrs, Bundle savedInstanceState)
Deprecated: See Fragment.onInflate(Context, AttributeSet, Bundle).
Called when a fragment is being created as part of a view layout
inflation, typically from setting the content view of an activity.
public void
onSaveInstanceState(Bundle outState)
Called to ask the fragment to save its current dynamic state, so it
can later be reconstructed in a new instance if its process is
restarted. If a new instance of the fragment later needs to be
created, the data you place in the Bundle here will be available
in the Bundle given to Fragment.onCreate(Bundle),
Fragment.onCreateView(LayoutInflater, ViewGroup, Bundle), and
Fragment.onViewCreated(View, Bundle).
This corresponds to and most of the discussion there
applies here as well. Note however: this method may be called
at any time before Fragment.onDestroy(). There are many situations
where a fragment may be mostly torn down (such as when placed on the
back stack with no UI showing), but its state will not be saved until
its owning activity actually needs to save its state.
Parameters:
outState: Bundle in which to place your saved state.
public void
onDestroyView()
Called when the view previously created by Fragment.onCreateView(LayoutInflater, ViewGroup, Bundle) has
been detached from the fragment. The next time the fragment needs
to be displayed, a new view will be created. This is called
after Fragment.onStop() and before Fragment.onDestroy(). It is called
regardless of whether Fragment.onCreateView(LayoutInflater, ViewGroup, Bundle) returned a
non-null view. Internally it is called after the view's state has
been saved but before it has been removed from its parent.
Source
/*
* Copyright (C) 2017 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package androidx.navigation.fragment;
import android.app.Dialog;
import android.content.Context;
import android.content.res.TypedArray;
import android.os.Bundle;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import androidx.annotation.CallSuper;
import androidx.annotation.NavigationRes;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.DialogFragment;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentContainerView;
import androidx.navigation.NavController;
import androidx.navigation.NavGraph;
import androidx.navigation.NavHost;
import androidx.navigation.NavHostController;
import androidx.navigation.Navigation;
import androidx.navigation.Navigator;
/**
* NavHostFragment provides an area within your layout for self-contained navigation to occur.
*
* <p>NavHostFragment is intended to be used as the content area within a layout resource
* defining your app's chrome around it, e.g.:</p>
*
* <pre class="prettyprint">
* <androidx.drawerlayout.widget.DrawerLayout
* xmlns:android="http://schemas.android.com/apk/res/android"
* xmlns:app="http://schemas.android.com/apk/res-auto"
* android:layout_width="match_parent"
* android:layout_height="match_parent">
* <fragment
* android:layout_width="match_parent"
* android:layout_height="match_parent"
* android:id="@+id/my_nav_host_fragment"
* android:name="androidx.navigation.fragment.NavHostFragment"
* app:navGraph="@navigation/nav_sample"
* app:defaultNavHost="true" />
* <android.support.design.widget.NavigationView
* android:layout_width="wrap_content"
* android:layout_height="match_parent"
* android:layout_gravity="start"/>
* </androidx.drawerlayout.widget.DrawerLayout>
* </pre>
*
* <p>Each NavHostFragment has a {@link NavController} that defines valid navigation within
* the navigation host. This includes the {@link NavGraph navigation graph} as well as navigation
* state such as current location and back stack that will be saved and restored along with the
* NavHostFragment itself.</p>
*
* <p>NavHostFragments register their navigation controller at the root of their view subtree
* such that any descendant can obtain the controller instance through the {@link Navigation}
* helper class's methods such as {@link Navigation#findNavController(View)}. View event listener
* implementations such as {@link android.view.View.OnClickListener} within navigation destination
* fragments can use these helpers to navigate based on user interaction without creating a tight
* coupling to the navigation host.</p>
*/
public class NavHostFragment extends Fragment implements NavHost {
private static final String KEY_GRAPH_ID = "android-support-nav:fragment:graphId";
private static final String KEY_START_DESTINATION_ARGS =
"android-support-nav:fragment:startDestinationArgs";
private static final String KEY_NAV_CONTROLLER_STATE =
"android-support-nav:fragment:navControllerState";
private static final String KEY_DEFAULT_NAV_HOST = "android-support-nav:fragment:defaultHost";
/**
* Find a {@link NavController} given a local {@link Fragment}.
*
* <p>This method will locate the {@link NavController} associated with this Fragment,
* looking first for a {@link NavHostFragment} along the given Fragment's parent chain.
* If a {@link NavController} is not found, this method will look for one along this
* Fragment's {@link Fragment#getView() view hierarchy} as specified by
* {@link Navigation#findNavController(View)}.</p>
*
* @param fragment the locally scoped Fragment for navigation
* @return the locally scoped {@link NavController} for navigating from this {@link Fragment}
* @throws IllegalStateException if the given Fragment does not correspond with a
* {@link NavHost} or is not within a NavHost.
*/
@NonNull
public static NavController findNavController(@NonNull Fragment fragment) {
Fragment findFragment = fragment;
while (findFragment != null) {
if (findFragment instanceof NavHostFragment) {
return ((NavHostFragment) findFragment).getNavController();
}
Fragment primaryNavFragment = findFragment.getParentFragmentManager()
.getPrimaryNavigationFragment();
if (primaryNavFragment instanceof NavHostFragment) {
return ((NavHostFragment) primaryNavFragment).getNavController();
}
findFragment = findFragment.getParentFragment();
}
// Try looking for one associated with the view instead, if applicable
View view = fragment.getView();
if (view != null) {
return Navigation.findNavController(view);
}
// For DialogFragments, look at the dialog's decor view
Dialog dialog = fragment instanceof DialogFragment
? ((DialogFragment) fragment).getDialog()
: null;
if (dialog != null && dialog.getWindow() != null) {
return Navigation.findNavController(dialog.getWindow().getDecorView());
}
throw new IllegalStateException("Fragment " + fragment
+ " does not have a NavController set");
}
private NavHostController mNavController;
private Boolean mIsPrimaryBeforeOnCreate = null;
private View mViewParent;
// State that will be saved and restored
private int mGraphId;
private boolean mDefaultNavHost;
/**
* Create a new NavHostFragment instance with an inflated {@link NavGraph} resource.
*
* @param graphResId resource id of the navigation graph to inflate
* @return a new NavHostFragment instance
*/
@NonNull
public static NavHostFragment create(@NavigationRes int graphResId) {
return create(graphResId, null);
}
/**
* Create a new NavHostFragment instance with an inflated {@link NavGraph} resource.
*
* @param graphResId resource id of the navigation graph to inflate
* @param startDestinationArgs arguments to send to the start destination of the graph
* @return a new NavHostFragment instance
*/
@NonNull
public static NavHostFragment create(@NavigationRes int graphResId,
@Nullable Bundle startDestinationArgs) {
Bundle b = null;
if (graphResId != 0) {
b = new Bundle();
b.putInt(KEY_GRAPH_ID, graphResId);
}
if (startDestinationArgs != null) {
if (b == null) {
b = new Bundle();
}
b.putBundle(KEY_START_DESTINATION_ARGS, startDestinationArgs);
}
final NavHostFragment result = new NavHostFragment();
if (b != null) {
result.setArguments(b);
}
return result;
}
/**
* Returns the {@link NavController navigation controller} for this navigation host.
* This method will return null until this host fragment's {@link #onCreate(Bundle)}
* has been called and it has had an opportunity to restore from a previous instance state.
*
* @return this host's navigation controller
* @throws IllegalStateException if called before {@link #onCreate(Bundle)}
*/
@NonNull
@Override
public final NavController getNavController() {
if (mNavController == null) {
throw new IllegalStateException("NavController is not available before onCreate()");
}
return mNavController;
}
@CallSuper
@Override
public void onAttach(@NonNull Context context) {
super.onAttach(context);
// TODO This feature should probably be a first-class feature of the Fragment system,
// but it can stay here until we can add the necessary attr resources to
// the fragment lib.
if (mDefaultNavHost) {
getParentFragmentManager().beginTransaction()
.setPrimaryNavigationFragment(this)
.commit();
}
}
@CallSuper
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
final Context context = requireContext();
mNavController = new NavHostController(context);
mNavController.setLifecycleOwner(this);
mNavController.setOnBackPressedDispatcher(requireActivity().getOnBackPressedDispatcher());
// Set the default state - this will be updated whenever
// onPrimaryNavigationFragmentChanged() is called
mNavController.enableOnBackPressed(
mIsPrimaryBeforeOnCreate != null && mIsPrimaryBeforeOnCreate);
mIsPrimaryBeforeOnCreate = null;
mNavController.setViewModelStore(getViewModelStore());
onCreateNavController(mNavController);
Bundle navState = null;
if (savedInstanceState != null) {
navState = savedInstanceState.getBundle(KEY_NAV_CONTROLLER_STATE);
if (savedInstanceState.getBoolean(KEY_DEFAULT_NAV_HOST, false)) {
mDefaultNavHost = true;
getParentFragmentManager().beginTransaction()
.setPrimaryNavigationFragment(this)
.commit();
}
mGraphId = savedInstanceState.getInt(KEY_GRAPH_ID);
}
if (navState != null) {
// Navigation controller state overrides arguments
mNavController.restoreState(navState);
}
if (mGraphId != 0) {
// Set from onInflate()
mNavController.setGraph(mGraphId);
} else {
// See if it was set by NavHostFragment.create()
final Bundle args = getArguments();
final int graphId = args != null ? args.getInt(KEY_GRAPH_ID) : 0;
final Bundle startDestinationArgs = args != null
? args.getBundle(KEY_START_DESTINATION_ARGS)
: null;
if (graphId != 0) {
mNavController.setGraph(graphId, startDestinationArgs);
}
}
// We purposefully run this last as this will trigger the onCreate() of
// child fragments, which may be relying on having the NavController already
// created and having its state restored by that point.
super.onCreate(savedInstanceState);
}
/**
* Callback for when the {@link #getNavController() NavController} is created. If you
* support any custom destination types, their {@link Navigator} should be added here to
* ensure it is available before the navigation graph is inflated / set.
* <p>
* By default, this adds a {@link FragmentNavigator}.
* <p>
* This is only called once in {@link #onCreate(Bundle)} and should not be called directly by
* subclasses.
*
* @param navController The newly created {@link NavController}.
*/
@SuppressWarnings({"WeakerAccess", "deprecation"})
@CallSuper
protected void onCreateNavController(@NonNull NavController navController) {
navController.getNavigatorProvider().addNavigator(
new DialogFragmentNavigator(requireContext(), getChildFragmentManager()));
navController.getNavigatorProvider().addNavigator(createFragmentNavigator());
}
// TODO: DialogFragmentNavigator should use FragmentOnAttachListener from Fragment 1.3
@SuppressWarnings("deprecation")
@Override
public void onAttachFragment(@NonNull Fragment childFragment) {
super.onAttachFragment(childFragment);
DialogFragmentNavigator dialogFragmentNavigator =
mNavController.getNavigatorProvider().getNavigator(DialogFragmentNavigator.class);
dialogFragmentNavigator.onAttachFragment(childFragment);
}
@CallSuper
@Override
public void onPrimaryNavigationFragmentChanged(boolean isPrimaryNavigationFragment) {
if (mNavController != null) {
mNavController.enableOnBackPressed(isPrimaryNavigationFragment);
} else {
mIsPrimaryBeforeOnCreate = isPrimaryNavigationFragment;
}
}
/**
* Create the FragmentNavigator that this NavHostFragment will use. By default, this uses
* {@link FragmentNavigator}, which replaces the entire contents of the NavHostFragment.
* <p>
* This is only called once in {@link #onCreate(Bundle)} and should not be called directly by
* subclasses.
* @return a new instance of a FragmentNavigator
* @deprecated Use {@link #onCreateNavController(NavController)}
*/
@SuppressWarnings("DeprecatedIsStillUsed")
@Deprecated
@NonNull
protected Navigator<? extends FragmentNavigator.Destination> createFragmentNavigator() {
return new FragmentNavigator(requireContext(), getChildFragmentManager(),
getContainerId());
}
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container,
@Nullable Bundle savedInstanceState) {
FragmentContainerView containerView = new FragmentContainerView(inflater.getContext());
// When added via XML, this has no effect (since this FragmentContainerView is given the ID
// automatically), but this ensures that the View exists as part of this Fragment's View
// hierarchy in cases where the NavHostFragment is added programmatically as is required
// for child fragment transactions
containerView.setId(getContainerId());
return containerView;
}
/**
* We specifically can't use {@link View#NO_ID} as the container ID (as we use
* {@link androidx.fragment.app.FragmentTransaction#add(int, Fragment)} under the hood),
* so we need to make sure we return a valid ID when asked for the container ID.
*
* @return a valid ID to be used to contain child fragments
*/
private int getContainerId() {
int id = getId();
if (id != 0 && id != View.NO_ID) {
return id;
}
// Fallback to using our own ID if this Fragment wasn't added via
// add(containerViewId, Fragment)
return R.id.nav_host_fragment_container;
}
@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
if (!(view instanceof ViewGroup)) {
throw new IllegalStateException("created host view " + view + " is not a ViewGroup");
}
Navigation.setViewNavController(view, mNavController);
// When added programmatically, we need to set the NavController on the parent - i.e.,
// the View that has the ID matching this NavHostFragment.
if (view.getParent() != null) {
mViewParent = (View) view.getParent();
if (mViewParent.getId() == getId()) {
Navigation.setViewNavController(mViewParent, mNavController);
}
}
}
@CallSuper
@Override
public void onInflate(@NonNull Context context, @NonNull AttributeSet attrs,
@Nullable Bundle savedInstanceState) {
super.onInflate(context, attrs, savedInstanceState);
final TypedArray navHost = context.obtainStyledAttributes(attrs,
androidx.navigation.R.styleable.NavHost);
final int graphId = navHost.getResourceId(
androidx.navigation.R.styleable.NavHost_navGraph, 0);
if (graphId != 0) {
mGraphId = graphId;
}
navHost.recycle();
final TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.NavHostFragment);
final boolean defaultHost = a.getBoolean(R.styleable.NavHostFragment_defaultNavHost, false);
if (defaultHost) {
mDefaultNavHost = true;
}
a.recycle();
}
@CallSuper
@Override
public void onSaveInstanceState(@NonNull Bundle outState) {
super.onSaveInstanceState(outState);
Bundle navState = mNavController.saveState();
if (navState != null) {
outState.putBundle(KEY_NAV_CONTROLLER_STATE, navState);
}
if (mDefaultNavHost) {
outState.putBoolean(KEY_DEFAULT_NAV_HOST, true);
}
if (mGraphId != 0) {
outState.putInt(KEY_GRAPH_ID, mGraphId);
}
}
@Override
public void onDestroyView() {
super.onDestroyView();
if (mViewParent != null && Navigation.findNavController(mViewParent) == mNavController) {
Navigation.setViewNavController(mViewParent, null);
}
mViewParent = null;
}
}