NavController.java

/*
 * 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;

import android.app.Activity;
import android.content.Context;
import android.content.ContextWrapper;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.os.Parcelable;
import android.util.Log;

import androidx.activity.OnBackPressedCallback;
import androidx.activity.OnBackPressedDispatcher;
import androidx.activity.OnBackPressedDispatcherOwner;
import androidx.annotation.CallSuper;
import androidx.annotation.IdRes;
import androidx.annotation.NavigationRes;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.core.app.TaskStackBuilder;
import androidx.lifecycle.LifecycleOwner;
import androidx.lifecycle.ViewModelStore;

import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Deque;
import java.util.Iterator;
import java.util.Map;
import java.util.UUID;
import java.util.concurrent.CopyOnWriteArrayList;

/**
 * NavController manages app navigation within a {@link NavHost}.
 *
 * <p>Apps will generally obtain a controller directly from a host, or by using one of the utility
 * methods on the {@link Navigation} class rather than create a controller directly.</p>
 *
 * <p>Navigation flows and destinations are determined by the
 * {@link NavGraph navigation graph} owned by the controller. These graphs are typically
 * {@link #getNavInflater() inflated} from an Android resource, but, like views, they can also
 * be constructed or combined programmatically or for the case of dynamic navigation structure.
 * (For example, if the navigation structure of the application is determined by live data obtained'
 * from a remote server.)</p>
 */
public class NavController {
    private static final String TAG = "NavController";
    private static final String KEY_NAVIGATOR_STATE =
            "android-support-nav:controller:navigatorState";
    private static final String KEY_NAVIGATOR_STATE_NAMES =
            "android-support-nav:controller:navigatorState:names";
    private static final String KEY_BACK_STACK_UUIDS =
            "android-support-nav:controller:backStackUUIDs";
    private static final String KEY_BACK_STACK_IDS = "android-support-nav:controller:backStackIds";
    private static final String KEY_BACK_STACK_ARGS =
            "android-support-nav:controller:backStackArgs";
    static final String KEY_DEEP_LINK_IDS = "android-support-nav:controller:deepLinkIds";
    static final String KEY_DEEP_LINK_EXTRAS =
            "android-support-nav:controller:deepLinkExtras";
    /**
     * The {@link Intent} that triggered a deep link to the current destination.
     */
    public static final @NonNull String KEY_DEEP_LINK_INTENT =
            "android-support-nav:controller:deepLinkIntent";

    private final Context mContext;
    private Activity mActivity;
    private NavInflater mInflater;
    private NavGraph mGraph;
    private Bundle mNavigatorStateToRestore;
    private String[] mBackStackUUIDsToRestore;
    private int[] mBackStackIdsToRestore;
    private Parcelable[] mBackStackArgsToRestore;

    private final Deque<NavBackStackEntry> mBackStack = new ArrayDeque<>();

    private LifecycleOwner mLifecycleOwner;
    private NavControllerViewModel mViewModel;

    private final NavigatorProvider mNavigatorProvider = new NavigatorProvider();

    private final CopyOnWriteArrayList<OnDestinationChangedListener>
            mOnDestinationChangedListeners = new CopyOnWriteArrayList<>();

    private final OnBackPressedCallback mOnBackPressedCallback =
            new OnBackPressedCallback(false) {
        @Override
        public void handleOnBackPressed() {
            popBackStack();
        }
    };

    /**
     * OnDestinationChangedListener receives a callback when the
     * {@link #getCurrentDestination()} or its arguments change.
     */
    public interface OnDestinationChangedListener {
        /**
         * Callback for when the {@link #getCurrentDestination()} or its arguments change.
         * This navigation may be to a destination that has not been seen before, or one that
         * was previously on the back stack. This method is called after navigation is complete,
         * but associated transitions may still be playing.
         *
         * @param controller the controller that navigated
         * @param destination the new destination
         * @param arguments the arguments passed to the destination
         */
        void onDestinationChanged(@NonNull NavController controller,
                @NonNull NavDestination destination, @Nullable Bundle arguments);
    }

    /**
     * Constructs a new controller for a given {@link Context}. Controllers should not be
     * used outside of their context and retain a hard reference to the context supplied.
     * If you need a global controller, pass {@link Context#getApplicationContext()}.
     *
     * <p>Apps should generally not construct controllers, instead obtain a relevant controller
     * directly from a navigation host via {@link NavHost#getNavController()} or by using one of
     * the utility methods on the {@link Navigation} class.</p>
     *
     * <p>Note that controllers that are not constructed with an {@link Activity} context
     * (or a wrapped activity context) will only be able to navigate to
     * {@link android.content.Intent#FLAG_ACTIVITY_NEW_TASK new tasks} or
     * {@link android.content.Intent#FLAG_ACTIVITY_NEW_DOCUMENT new document tasks} when
     * navigating to new activities.</p>
     *
     * @param context context for this controller
     */
    public NavController(@NonNull Context context) {
        mContext = context;
        while (context instanceof ContextWrapper) {
            if (context instanceof Activity) {
                mActivity = (Activity) context;
                break;
            }
            context = ((ContextWrapper) context).getBaseContext();
        }
        mNavigatorProvider.addNavigator(new NavGraphNavigator(mNavigatorProvider));
        mNavigatorProvider.addNavigator(new ActivityNavigator(mContext));
    }

    @NonNull
    Context getContext() {
        return mContext;
    }

    /**
     * Retrieve the NavController's {@link NavigatorProvider}. All {@link Navigator Navigators} used
     * to construct the {@link NavGraph navigation graph} for this nav controller should be added
     * to this navigator provider before the graph is constructed.
     * <p>
     * Generally, the Navigators are set for you by the {@link NavHost} hosting this NavController
     * and you do not need to manually interact with the navigator provider.
     * </p>
     * @return The {@link NavigatorProvider} used by this NavController.
     */
    @NonNull
    public NavigatorProvider getNavigatorProvider() {
        return mNavigatorProvider;
    }

    /**
     * Adds an {@link OnDestinationChangedListener} to this controller to receive a callback
     * whenever the {@link #getCurrentDestination()} or its arguments change.
     *
     * <p>The current destination, if any, will be immediately sent to your listener.</p>
     *
     * @param listener the listener to receive events
     */
    public void addOnDestinationChangedListener(@NonNull OnDestinationChangedListener listener) {
        // Inform the new listener of our current state, if any
        if (!mBackStack.isEmpty()) {
            NavBackStackEntry backStackEntry = mBackStack.peekLast();
            listener.onDestinationChanged(this, backStackEntry.getDestination(),
                    backStackEntry.getArguments());
        }
        mOnDestinationChangedListeners.add(listener);
    }

    /**
     * Removes an {@link OnDestinationChangedListener} from this controller.
     * It will no longer receive callbacks.
     *
     * @param listener the listener to remove
     */
    public void removeOnDestinationChangedListener(
            @NonNull OnDestinationChangedListener listener) {
        mOnDestinationChangedListeners.remove(listener);
    }

    /**
     * Attempts to pop the controller's back stack. Analogous to when the user presses
     * the system {@link android.view.KeyEvent#KEYCODE_BACK Back} button when the associated
     * navigation host has focus.
     *
     * @return true if the stack was popped and the user has been navigated to another
     * destination, false otherwise
     */
    public boolean popBackStack() {
        if (mBackStack.isEmpty()) {
            // Nothing to pop if the back stack is empty
            return false;
        }
        // Pop just the current destination off the stack
        return popBackStack(getCurrentDestination().getId(), true);
    }

    /**
     * Attempts to pop the controller's back stack back to a specific destination.
     *
     * @param destinationId The topmost destination to retain
     * @param inclusive Whether the given destination should also be popped.
     *
     * @return true if the stack was popped at least once and the user has been navigated to
     * another destination, false otherwise
     */
    public boolean popBackStack(@IdRes int destinationId, boolean inclusive) {
        boolean popped = popBackStackInternal(destinationId, inclusive);
        // Only return true if the pop succeeded and we've dispatched
        // the change to a new destination
        return popped && dispatchOnDestinationChanged();
    }

    /**
     * Attempts to pop the controller's back stack back to a specific destination. This does
     * <strong>not</strong> handle calling {@link #dispatchOnDestinationChanged()}
     *
     * @param destinationId The topmost destination to retain
     * @param inclusive Whether the given destination should also be popped.
     *
     * @return true if the stack was popped at least once, false otherwise
     */
    @SuppressWarnings("WeakerAccess") /* synthetic access */
    boolean popBackStackInternal(@IdRes int destinationId, boolean inclusive) {
        if (mBackStack.isEmpty()) {
            // Nothing to pop if the back stack is empty
            return false;
        }
        ArrayList<Navigator> popOperations = new ArrayList<>();
        Iterator<NavBackStackEntry> iterator = mBackStack.descendingIterator();
        boolean foundDestination = false;
        while (iterator.hasNext()) {
            NavDestination destination = iterator.next().getDestination();
            Navigator navigator = mNavigatorProvider.getNavigator(
                    destination.getNavigatorName());
            if (inclusive || destination.getId() != destinationId) {
                popOperations.add(navigator);
            }
            if (destination.getId() == destinationId) {
                foundDestination = true;
                break;
            }
        }
        if (!foundDestination) {
            // We were passed a destinationId that doesn't exist on our back stack.
            // Better to ignore the popBackStack than accidentally popping the entire stack
            String destinationName = NavDestination.getDisplayName(mContext, destinationId);
            Log.i(TAG, "Ignoring popBackStack to destination " + destinationName
                    + " as it was not found on the current back stack");
            return false;
        }
        boolean popped = false;
        for (Navigator navigator : popOperations) {
            if (navigator.popBackStack()) {
                NavBackStackEntry entry = mBackStack.removeLast();
                if (mViewModel != null) {
                    mViewModel.clear(entry.mId);
                }
                popped = true;
            } else {
                // The pop did not complete successfully, so stop immediately
                break;
            }
        }
        mOnBackPressedCallback.setEnabled(getDestinationCountOnBackStack() > 1);
        return popped;
    }

    /**
     * Attempts to navigate up in the navigation hierarchy. Suitable for when the
     * user presses the "Up" button marked with a left (or start)-facing arrow in the upper left
     * (or starting) corner of the app UI.
     *
     * <p>The intended behavior of Up differs from {@link #popBackStack() Back} when the user
     * did not reach the current destination from the application's own task. e.g. if the user
     * is viewing a document or link in the current app in an activity hosted on another app's
     * task where the user clicked the link. In this case the current activity (determined by the
     * context used to create this NavController) will be {@link Activity#finish() finished} and
     * the user will be taken to an appropriate destination in this app on its own task.</p>
     *
     * @return true if navigation was successful, false otherwise
     */
    public boolean navigateUp() {
        if (getDestinationCountOnBackStack() == 1) {
            // If there's only one entry, then we've deep linked into a specific destination
            // on another task so we need to find the parent and start our task from there
            NavDestination currentDestination = getCurrentDestination();
            int destId = currentDestination.getId();
            NavGraph parent = currentDestination.getParent();
            while (parent != null) {
                if (parent.getStartDestination() != destId) {
                    TaskStackBuilder parentIntents = new NavDeepLinkBuilder(this)
                            .setDestination(parent.getId())
                            .createTaskStackBuilder();
                    parentIntents.startActivities();
                    if (mActivity != null) {
                        mActivity.finish();
                    }
                    return true;
                }
                destId = parent.getId();
                parent = parent.getParent();
            }
            // We're already at the startDestination of the graph so there's no 'Up' to go to
            return false;
        } else {
            return popBackStack();
        }
    }

    /**
     * Gets the number of non-NavGraph destinations on the back stack
     */
    private int getDestinationCountOnBackStack() {
        int count = 0;
        for (NavBackStackEntry entry : mBackStack) {
            if (!(entry.getDestination() instanceof NavGraph)) {
                count++;
            }
        }
        return count;
    }

    /**
     * Dispatch changes to all OnDestinationChangedListeners.
     * <p>
     * If the back stack is empty, no events get dispatched.
     *
     * @return If changes were dispatched.
     */
    private boolean dispatchOnDestinationChanged() {
        // We never want to leave NavGraphs on the top of the stack
        //noinspection StatementWithEmptyBody
        while (!mBackStack.isEmpty()
                && mBackStack.peekLast().getDestination() instanceof NavGraph
                && popBackStackInternal(mBackStack.peekLast().getDestination().getId(), true)) {
            // Keep popping
        }
        if (!mBackStack.isEmpty()) {
            NavBackStackEntry backStackEntry = mBackStack.peekLast();
            for (OnDestinationChangedListener listener :
                    mOnDestinationChangedListeners) {
                listener.onDestinationChanged(this, backStackEntry.getDestination(),
                        backStackEntry.getArguments());
            }
            return true;
        }
        return false;
    }

    /**
     * Returns the {@link NavInflater inflater} for this controller.
     *
     * @return inflater for loading navigation resources
     */
    @NonNull
    public NavInflater getNavInflater() {
        if (mInflater == null) {
            mInflater = new NavInflater(mContext, mNavigatorProvider);
        }
        return mInflater;
    }

    /**
     * Sets the {@link NavGraph navigation graph} to the specified resource.
     * Any current navigation graph data (including back stack) will be replaced.
     *
     * <p>The inflated graph can be retrieved via {@link #getGraph()}.</p>
     *
     * @param graphResId resource id of the navigation graph to inflate
     *
     * @see #getNavInflater()
     * @see #setGraph(NavGraph)
     * @see #getGraph
     */
    @CallSuper
    public void setGraph(@NavigationRes int graphResId) {
        setGraph(graphResId, null);
    }

    /**
     * Sets the {@link NavGraph navigation graph} to the specified resource.
     * Any current navigation graph data (including back stack) will be replaced.
     *
     * <p>The inflated graph can be retrieved via {@link #getGraph()}.</p>
     *
     * @param graphResId resource id of the navigation graph to inflate
     * @param startDestinationArgs arguments to send to the start destination of the graph
     *
     * @see #getNavInflater()
     * @see #setGraph(NavGraph, Bundle)
     * @see #getGraph
     */
    @CallSuper
    public void setGraph(@NavigationRes int graphResId, @Nullable Bundle startDestinationArgs) {
        setGraph(getNavInflater().inflate(graphResId), startDestinationArgs);
    }

    /**
     * Sets the {@link NavGraph navigation graph} to the specified graph.
     * Any current navigation graph data (including back stack) will be replaced.
     *
     * <p>The graph can be retrieved later via {@link #getGraph()}.</p>
     *
     * @param graph graph to set
     * @see #setGraph(int)
     * @see #getGraph
     */
    @CallSuper
    public void setGraph(@NonNull NavGraph graph) {
        setGraph(graph, null);
    }

    /**
     * Sets the {@link NavGraph navigation graph} to the specified graph.
     * Any current navigation graph data (including back stack) will be replaced.
     *
     * <p>The graph can be retrieved later via {@link #getGraph()}.</p>
     *
     * @param graph graph to set
     * @see #setGraph(int, Bundle)
     * @see #getGraph
     */
    @CallSuper
    public void setGraph(@NonNull NavGraph graph, @Nullable Bundle startDestinationArgs) {
        if (mGraph != null) {
            // Pop everything from the old graph off the back stack
            popBackStackInternal(mGraph.getId(), true);
        }
        mGraph = graph;
        onGraphCreated(startDestinationArgs);
    }

    private void onGraphCreated(@Nullable Bundle startDestinationArgs) {
        if (mNavigatorStateToRestore != null) {
            ArrayList<String> navigatorNames = mNavigatorStateToRestore.getStringArrayList(
                    KEY_NAVIGATOR_STATE_NAMES);
            if (navigatorNames != null) {
                for (String name : navigatorNames) {
                    Navigator navigator = mNavigatorProvider.getNavigator(name);
                    Bundle bundle = mNavigatorStateToRestore.getBundle(name);
                    if (bundle != null) {
                        navigator.onRestoreState(bundle);
                    }
                }
            }
        }
        if (mBackStackUUIDsToRestore != null) {
            for (int index = 0; index < mBackStackUUIDsToRestore.length; index++) {
                UUID uuid = UUID.fromString(mBackStackUUIDsToRestore[index]);
                int destinationId = mBackStackIdsToRestore[index];
                Bundle args = (Bundle) mBackStackArgsToRestore[index];
                NavDestination node = findDestination(destinationId);
                if (node == null) {
                    throw new IllegalStateException("unknown destination during restore: "
                            + mContext.getResources().getResourceName(destinationId));
                }
                if (args != null) {
                    args.setClassLoader(mContext.getClassLoader());
                }
                mBackStack.add(new NavBackStackEntry(uuid, node, args));
            }
            mOnBackPressedCallback.setEnabled(getDestinationCountOnBackStack() > 1);
            mBackStackUUIDsToRestore = null;
            mBackStackIdsToRestore = null;
            mBackStackArgsToRestore = null;
        }
        if (mGraph != null && mBackStack.isEmpty()) {
            boolean deepLinked = mActivity != null && handleDeepLink(mActivity.getIntent());
            if (!deepLinked) {
                // Navigate to the first destination in the graph
                // if we haven't deep linked to a destination
                navigate(mGraph, startDestinationArgs, null, null);
            }
        }
    }

    /**
     * Checks the given Intent for a Navigation deep link and navigates to the deep link if present.
     * This is called automatically for you the first time you set the graph if you've passed in an
     * {@link Activity} as the context when constructing this NavController, but should be manually
     * called if your Activity receives new Intents in {@link Activity#onNewIntent(Intent)}.
     * <p>
     * The types of Intents that are supported include:
     * <ul>
     *     <ol>Intents created by {@link NavDeepLinkBuilder} or
     *     {@link #createDeepLink()}. This assumes that the current graph shares
     *     the same hierarchy to get to the deep linked destination as when the deep link was
     *     constructed.</ol>
     *     <ol>Intents that include a {@link Intent#getData() data Uri}. This Uri will be checked
     *     against the Uri patterns added via {@link NavDestination#addDeepLink(String)}.</ol>
     * </ul>
     * <p>The {@link #getGraph() navigation graph} should be set before calling this method.</p>
     * @param intent The Intent that may contain a valid deep link
     * @return True if the navigation controller found a valid deep link and navigated to it.
     * @see NavDestination#addDeepLink(String)
     */
    public boolean handleDeepLink(@Nullable Intent intent) {
        if (intent == null) {
            return false;
        }
        Bundle extras = intent.getExtras();
        int[] deepLink = extras != null ? extras.getIntArray(KEY_DEEP_LINK_IDS) : null;
        Bundle bundle = new Bundle();
        Bundle deepLinkExtras = extras != null ? extras.getBundle(KEY_DEEP_LINK_EXTRAS) : null;
        if (deepLinkExtras != null) {
            bundle.putAll(deepLinkExtras);
        }
        if ((deepLink == null || deepLink.length == 0) && intent.getData() != null) {
            NavDestination.DeepLinkMatch matchingDeepLink = mGraph.matchDeepLink(intent.getData());
            if (matchingDeepLink != null) {
                deepLink = matchingDeepLink.getDestination().buildDeepLinkIds();
                bundle.putAll(matchingDeepLink.getMatchingArgs());
            }
        }
        if (deepLink == null || deepLink.length == 0) {
            return false;
        }
        String invalidDestinationDisplayName =
                findInvalidDestinationDisplayNameInDeepLink(deepLink);
        if (invalidDestinationDisplayName != null) {
            Log.i(TAG, "Could not find destination " + invalidDestinationDisplayName
                    + " in the navigation graph, ignoring the deep link from " + intent);
            return false;
        }
        bundle.putParcelable(KEY_DEEP_LINK_INTENT, intent);
        int flags = intent.getFlags();
        if ((flags & Intent.FLAG_ACTIVITY_NEW_TASK) != 0
                && (flags & Intent.FLAG_ACTIVITY_CLEAR_TASK) == 0) {
            // Someone called us with NEW_TASK, but we don't know what state our whole
            // task stack is in, so we need to manually restart the whole stack to
            // ensure we're in a predictably good state.
            intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK);
            TaskStackBuilder taskStackBuilder = TaskStackBuilder
                    .create(mContext)
                    .addNextIntentWithParentStack(intent);
            taskStackBuilder.startActivities();
            if (mActivity != null) {
                mActivity.finish();
            }
            return true;
        }
        if ((flags & Intent.FLAG_ACTIVITY_NEW_TASK) != 0) {
            // Start with a cleared task starting at our root when we're on our own task
            if (!mBackStack.isEmpty()) {
                popBackStackInternal(mGraph.getId(), true);
            }
            int index = 0;
            while (index < deepLink.length) {
                int destinationId = deepLink[index++];
                NavDestination node = findDestination(destinationId);
                if (node == null) {
                    throw new IllegalStateException("unknown destination during deep link: "
                            + NavDestination.getDisplayName(mContext, destinationId));
                }
                navigate(node, bundle,
                        new NavOptions.Builder().setEnterAnim(0).setExitAnim(0).build(), null);
            }
            return true;
        }
        // Assume we're on another apps' task and only start the final destination
        NavGraph graph = mGraph;
        for (int i = 0; i < deepLink.length; i++) {
            int destinationId = deepLink[i];
            NavDestination node = i == 0 ? mGraph : graph.findNode(destinationId);
            if (node == null) {
                throw new IllegalStateException("unknown destination during deep link: "
                        + NavDestination.getDisplayName(mContext, destinationId));
            }
            if (i != deepLink.length - 1) {
                // We're not at the final NavDestination yet, so keep going through the chain
                graph = (NavGraph) node;
                // Automatically go down the navigation graph when
                // the start destination is also a NavGraph
                while (graph.findNode(graph.getStartDestination()) instanceof NavGraph) {
                    graph = (NavGraph) graph.findNode(graph.getStartDestination());
                }
            } else {
                // Navigate to the last NavDestination, clearing any existing destinations
                navigate(node, node.addInDefaultArgs(bundle), new NavOptions.Builder()
                        .setPopUpTo(mGraph.getId(), true)
                        .setEnterAnim(0).setExitAnim(0).build(), null);
            }
        }
        return true;
    }

    /**
     * Looks through the deep link for invalid destinations, returning the display name of
     * any invalid destinations in the deep link array.
     *
     * @param deepLink array of deep link IDs that are expected to match the graph
     * @return The display name of the first destination not found in the graph or null if
     * all destinations were found in the graph.
     */
    @Nullable
    private String findInvalidDestinationDisplayNameInDeepLink(@NonNull int[] deepLink) {
        NavGraph graph = mGraph;
        for (int i = 0; i < deepLink.length; i++) {
            int destinationId = deepLink[i];
            NavDestination node = i == 0 ? mGraph : graph.findNode(destinationId);
            if (node == null) {
                return NavDestination.getDisplayName(mContext, destinationId);
            }
            if (i != deepLink.length - 1) {
                // We're not at the final NavDestination yet, so keep going through the chain
                graph = (NavGraph) node;
                // Automatically go down the navigation graph when
                // the start destination is also a NavGraph
                while (graph.findNode(graph.getStartDestination()) instanceof NavGraph) {
                    graph = (NavGraph) graph.findNode(graph.getStartDestination());
                }
            }
        }
        // We found every destination in the deepLink array, yay!
        return null;
    }

    /**
     * Gets the topmost navigation graph associated with this NavController.
     *
     * @see #setGraph(int)
     * @see #setGraph(NavGraph)
     * @throws IllegalStateException if called before <code>setGraph()</code>.
     */
    @NonNull
    public NavGraph getGraph() {
        if (mGraph == null) {
            throw new IllegalStateException("You must call setGraph() before calling getGraph()");
        }
        return mGraph;
    }

    /**
     * Gets the current destination.
     */
    @Nullable
    public NavDestination getCurrentDestination() {
        if (mBackStack.isEmpty()) {
            return null;
        } else {
            return mBackStack.getLast().getDestination();
        }
    }

    @SuppressWarnings("WeakerAccess") /* synthetic access */
    NavDestination findDestination(@IdRes int destinationId) {
        if (mGraph == null) {
            return null;
        }
        if (mGraph.getId() == destinationId) {
            return mGraph;
        }
        NavDestination currentNode = mBackStack.isEmpty()
                ? mGraph
                : mBackStack.getLast().getDestination();
        NavGraph currentGraph = currentNode instanceof NavGraph
                ? (NavGraph) currentNode
                : currentNode.getParent();
        return currentGraph.findNode(destinationId);
    }

    /**
     * Navigate to a destination from the current navigation graph. This supports both navigating
     * via an {@link NavDestination#getAction(int) action} and directly navigating to a destination.
     *
     * @param resId an {@link NavDestination#getAction(int) action} id or a destination id to
     *              navigate to
     */
    public void navigate(@IdRes int resId) {
        navigate(resId, null);
    }

    /**
     * Navigate to a destination from the current navigation graph. This supports both navigating
     * via an {@link NavDestination#getAction(int) action} and directly navigating to a destination.
     *
     * @param resId an {@link NavDestination#getAction(int) action} id or a destination id to
     *              navigate to
     * @param args arguments to pass to the destination
     */
    public void navigate(@IdRes int resId, @Nullable Bundle args) {
        navigate(resId, args, null);
    }

    /**
     * Navigate to a destination from the current navigation graph. This supports both navigating
     * via an {@link NavDestination#getAction(int) action} and directly navigating to a destination.
     *
     * @param resId an {@link NavDestination#getAction(int) action} id or a destination id to
     *              navigate to
     * @param args arguments to pass to the destination
     * @param navOptions special options for this navigation operation
     */
    public void navigate(@IdRes int resId, @Nullable Bundle args,
            @Nullable NavOptions navOptions) {
        navigate(resId, args, navOptions, null);
    }

    /**
     * Navigate to a destination from the current navigation graph. This supports both navigating
     * via an {@link NavDestination#getAction(int) action} and directly navigating to a destination.
     *
     * @param resId an {@link NavDestination#getAction(int) action} id or a destination id to
     *              navigate to
     * @param args arguments to pass to the destination
     * @param navOptions special options for this navigation operation
     * @param navigatorExtras extras to pass to the Navigator
     */
    @SuppressWarnings("deprecation")
    public void navigate(@IdRes int resId, @Nullable Bundle args, @Nullable NavOptions navOptions,
            @Nullable Navigator.Extras navigatorExtras) {
        NavDestination currentNode = mBackStack.isEmpty()
                ? mGraph
                : mBackStack.getLast().getDestination();
        if (currentNode == null) {
            throw new IllegalStateException("no current navigation node");
        }
        @IdRes int destId = resId;
        final NavAction navAction = currentNode.getAction(resId);
        Bundle combinedArgs = null;
        if (navAction != null) {
            if (navOptions == null) {
                navOptions = navAction.getNavOptions();
            }
            destId = navAction.getDestinationId();
            Bundle navActionArgs = navAction.getDefaultArguments();
            if (navActionArgs != null) {
                combinedArgs = new Bundle();
                combinedArgs.putAll(navActionArgs);
            }
        }

        if (args != null) {
            if (combinedArgs == null) {
                combinedArgs = new Bundle();
            }
            combinedArgs.putAll(args);
        }

        if (destId == 0 && navOptions != null && navOptions.getPopUpTo() != -1) {
            popBackStack(navOptions.getPopUpTo(), navOptions.isPopUpToInclusive());
            return;
        }

        if (destId == 0) {
            throw new IllegalArgumentException("Destination id == 0 can only be used"
                    + " in conjunction with a valid navOptions.popUpTo");
        }

        NavDestination node = findDestination(destId);
        if (node == null) {
            final String dest = NavDestination.getDisplayName(mContext, destId);
            throw new IllegalArgumentException("navigation destination " + dest
                    + (navAction != null
                    ? " referenced from action " + NavDestination.getDisplayName(mContext, resId)
                    : "")
                    + " is unknown to this NavController");
        }
        navigate(node, combinedArgs, navOptions, navigatorExtras);
    }

    /**
     * Navigate to a destination via the given deep link {@link Uri}.
     * {@link NavDestination#hasDeepLink(Uri)} should be called on
     * {@link #getGraph() the navigation graph} prior to calling this method to check if the deep
     * link is valid. If an invalid deep link is given, an {@link IllegalArgumentException} will be
     * thrown.
     *
     * @param deepLink deepLink to the destination reachable from the current NavGraph
     */
    public void navigate(@NonNull Uri deepLink) {
        navigate(deepLink, null);
    }

    /**
     * Navigate to a destination via the given deep link {@link Uri}.
     * {@link NavDestination#hasDeepLink(Uri)} should be called on
     * {@link #getGraph() the navigation graph} prior to calling this method to check if the deep
     * link is valid. If an invalid deep link is given, an {@link IllegalArgumentException} will be
     * thrown.
     *
     * @param deepLink deepLink to the destination reachable from the current NavGraph
     * @param navOptions special options for this navigation operation
     */
    public void navigate(@NonNull Uri deepLink, @Nullable NavOptions navOptions) {
        navigate(deepLink, navOptions, null);
    }

    /**
     * Navigate to a destination via the given deep link {@link Uri}.
     * {@link NavDestination#hasDeepLink(Uri)} should be called on
     * {@link #getGraph() the navigation graph} prior to calling this method to check if the deep
     * link is valid. If an invalid deep link is given, an {@link IllegalArgumentException} will be
     * thrown.
     *
     * @param deepLink deepLink to the destination reachable from the current NavGraph
     * @param navOptions special options for this navigation operation
     * @param navigatorExtras extras to pass to the Navigator
     */
    public void navigate(@NonNull Uri deepLink, @Nullable NavOptions navOptions,
            @Nullable Navigator.Extras navigatorExtras) {
        NavDestination.DeepLinkMatch deepLinkMatch = mGraph.matchDeepLink(deepLink);
        if (deepLinkMatch != null) {
            Bundle args = deepLinkMatch.getMatchingArgs();
            NavDestination node = deepLinkMatch.getDestination();
            navigate(node, args, navOptions, navigatorExtras);
        } else {
            throw new IllegalArgumentException("navigation destination with deepLink "
                    + deepLink + " is unknown to this NavController");
        }
    }

    private void navigate(@NonNull NavDestination node, @Nullable Bundle args,
            @Nullable NavOptions navOptions, @Nullable Navigator.Extras navigatorExtras) {
        boolean popped = false;
        if (navOptions != null) {
            if (navOptions.getPopUpTo() != -1) {
                popped = popBackStackInternal(navOptions.getPopUpTo(),
                        navOptions.isPopUpToInclusive());
            }
        }
        Navigator<NavDestination> navigator = mNavigatorProvider.getNavigator(
                node.getNavigatorName());
        Bundle finalArgs = node.addInDefaultArgs(args);
        NavDestination newDest = navigator.navigate(node, finalArgs,
                navOptions, navigatorExtras);
        if (newDest != null) {
            // Ensure that every parent NavGraph is also on the stack if it isn't already
            // First get all of the parent NavGraphs
            ArrayDeque<NavBackStackEntry> hierarchy = new ArrayDeque<>();
            NavGraph parent = newDest.getParent();
            while (parent != null) {
                hierarchy.addFirst(new NavBackStackEntry(parent, finalArgs));
                parent = parent.getParent();
            }
            // Now iterate through the back stack and see which NavGraphs
            // are already on the back stack
            Iterator<NavBackStackEntry> iterator = mBackStack.iterator();
            while (iterator.hasNext() && !hierarchy.isEmpty()) {
                NavDestination destination = iterator.next().getDestination();
                if (destination.equals(hierarchy.getFirst().getDestination())) {
                    // This destination is already in the back stack so
                    // we don't need to add it
                    hierarchy.removeFirst();
                }
            }
            // Add all of the remaining parent NavGraphs that aren't
            // already on the back stack
            mBackStack.addAll(hierarchy);
            // And finally, add the new destination with its default args
            NavBackStackEntry newBackStackEntry = new NavBackStackEntry(newDest,
                    newDest.addInDefaultArgs(finalArgs));
            mBackStack.add(newBackStackEntry);
        }
        mOnBackPressedCallback.setEnabled(getDestinationCountOnBackStack() > 1);
        if (popped || newDest != null) {
            dispatchOnDestinationChanged();
        }
    }

    /**
     * Navigate via the given {@link NavDirections}
     *
     * @param directions directions that describe this navigation operation
     */
    public void navigate(@NonNull NavDirections directions) {
        navigate(directions.getActionId(), directions.getArguments());
    }

    /**
     * Navigate via the given {@link NavDirections}
     *
     * @param directions directions that describe this navigation operation
     * @param navOptions special options for this navigation operation
     */
    public void navigate(@NonNull NavDirections directions, @Nullable NavOptions navOptions) {
        navigate(directions.getActionId(), directions.getArguments(), navOptions);
    }

    /**
     * Navigate via the given {@link NavDirections}
     *
     * @param directions directions that describe this navigation operation
     * @param navigatorExtras extras to pass to the {@link Navigator}
     */
    public void navigate(@NonNull NavDirections directions,
            @NonNull Navigator.Extras navigatorExtras) {
        navigate(directions.getActionId(), directions.getArguments(), null, navigatorExtras);
    }

    /**
     * Create a deep link to a destination within this NavController.
     *
     * @return a {@link NavDeepLinkBuilder} suitable for constructing a deep link
     */
    @NonNull
    public NavDeepLinkBuilder createDeepLink() {
        return new NavDeepLinkBuilder(this);
    }

    /**
     * Saves all navigation controller state to a Bundle.
     *
     * <p>State may be restored from a bundle returned from this method by calling
     * {@link #restoreState(Bundle)}. Saving controller state is the responsibility
     * of a {@link NavHost}.</p>
     *
     * @return saved state for this controller
     */
    @CallSuper
    @Nullable
    public Bundle saveState() {
        Bundle b = null;
        ArrayList<String> navigatorNames = new ArrayList<>();
        Bundle navigatorState = new Bundle();
        for (Map.Entry<String, Navigator<? extends NavDestination>> entry :
                mNavigatorProvider.getNavigators().entrySet()) {
            String name = entry.getKey();
            Bundle savedState = entry.getValue().onSaveState();
            if (savedState != null) {
                navigatorNames.add(name);
                navigatorState.putBundle(name, savedState);
            }
        }
        if (!navigatorNames.isEmpty()) {
            b = new Bundle();
            navigatorState.putStringArrayList(KEY_NAVIGATOR_STATE_NAMES, navigatorNames);
            b.putBundle(KEY_NAVIGATOR_STATE, navigatorState);
        }
        if (!mBackStack.isEmpty()) {
            if (b == null) {
                b = new Bundle();
            }
            String[] backStackUUIDs = new String[mBackStack.size()];
            int[] backStackIds = new int[mBackStack.size()];
            Parcelable[] backStackArgs = new Parcelable[mBackStack.size()];
            int index = 0;
            for (NavBackStackEntry backStackEntry : mBackStack) {
                backStackUUIDs[index] = backStackEntry.mId.toString();
                backStackIds[index] = backStackEntry.getDestination().getId();
                backStackArgs[index++] = backStackEntry.getArguments();
            }
            b.putStringArray(KEY_BACK_STACK_UUIDS, backStackUUIDs);
            b.putIntArray(KEY_BACK_STACK_IDS, backStackIds);
            b.putParcelableArray(KEY_BACK_STACK_ARGS, backStackArgs);
        }
        return b;
    }

    /**
     * Restores all navigation controller state from a bundle. This should be called before any
     * call to {@link #setGraph}.
     *
     * <p>State may be saved to a bundle by calling {@link #saveState()}.
     * Restoring controller state is the responsibility of a {@link NavHost}.</p>
     *
     * @param navState state bundle to restore
     */
    @CallSuper
    public void restoreState(@Nullable Bundle navState) {
        if (navState == null) {
            return;
        }

        navState.setClassLoader(mContext.getClassLoader());

        mNavigatorStateToRestore = navState.getBundle(KEY_NAVIGATOR_STATE);
        mBackStackUUIDsToRestore = navState.getStringArray(KEY_BACK_STACK_UUIDS);
        mBackStackIdsToRestore = navState.getIntArray(KEY_BACK_STACK_IDS);
        mBackStackArgsToRestore = navState.getParcelableArray(KEY_BACK_STACK_ARGS);
    }

    /**
     * Sets the host's {@link LifecycleOwner}.
     *
     * @param owner The {@link LifecycleOwner} associated with the containing {@link NavHost}.
     * @see #setHostOnBackPressedDispatcherOwner(OnBackPressedDispatcherOwner)
     */
    public void setHostLifecycleOwner(@NonNull LifecycleOwner owner) {
        mLifecycleOwner = owner;
    }

    /**
     * Sets the host's {@link OnBackPressedDispatcherOwner}. If set, NavController will
     * register a {@link OnBackPressedCallback} to handle system Back button events.
     * <p>
     * If you have not explicitly called {@link #setHostLifecycleOwner(LifecycleOwner)},
     * the owner you pass here will be used as the {@link LifecycleOwner} for registering
     * the {@link OnBackPressedCallback}.
     *
     * @param owner The {@link OnBackPressedDispatcherOwner} associated with the containing
     * {@link NavHost}.
     * @see #setHostLifecycleOwner(LifecycleOwner)
     */
    public void setHostOnBackPressedDispatcherOwner(@NonNull OnBackPressedDispatcherOwner owner) {
        if (mLifecycleOwner == null) {
            mLifecycleOwner = owner;
        }
        OnBackPressedDispatcher dispatcher = owner.getOnBackPressedDispatcher();
        // Remove the callback from any previous dispatcher
        mOnBackPressedCallback.remove();
        // Then add it to the new dispatcher
        dispatcher.addCallback(mLifecycleOwner, mOnBackPressedCallback);
    }

    /**
     * Sets the host's ViewModelStore used by the NavController to store ViewModels at the
     * navigation graph level. This is required to call {@link #getViewModelStore} and
     * should generally be called for you by your {@link NavHost}.
     *
     * @param viewModelStore ViewModelStore used to store ViewModels at the navigation graph level
     */
    public void setHostViewModelStore(@NonNull ViewModelStore viewModelStore) {
        mViewModel = NavControllerViewModel.getInstance(viewModelStore);
    }

    /**
     * Gets the view model for a NavGraph. If a view model does not exist it will create and
     * store one.
     *
     * @param navGraphId ID of a NavGraph that exists on the back stack
     * @throws IllegalStateException if called before {@link #setHostViewModelStore}.
     * @throws IllegalArgumentException if the NavGraph is not on the back stack
     */
    @NonNull
    public ViewModelStore getViewModelStore(@IdRes int navGraphId) {
        if (mViewModel == null) {
            throw new IllegalStateException("You must call setViewModelStore() before calling "
                    + "getViewModelStore().");
        }
        NavBackStackEntry lastFromBackStack = null;
        Iterator<NavBackStackEntry> iterator = mBackStack.descendingIterator();
        while (iterator.hasNext()) {
            NavBackStackEntry entry = iterator.next();
            NavDestination destination = entry.getDestination();
            if (destination instanceof NavGraph && destination.getId() == navGraphId) {
                lastFromBackStack = entry;
                break;
            }
        }
        if (lastFromBackStack == null) {
            throw new IllegalArgumentException("No NavGraph with ID " + navGraphId + " is on the "
                    + "NavController's back stack");
        }
        return mViewModel.getViewModelStore(lastFromBackStack.mId);
    }
}