Activity not showing using NavController

I have a java app for android using bottom navigation activity. The application worked well, but the state of the fragments was not saved during the transition. To solve this problem, I decided to make my own FragmentNavigator. Now when I use my fragment instead of the standard fragment in xml layout, I get the following error:

E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.wasd, PID: 13588
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.mobileapp/com.example.mobileapp.AccountMainActivity}: android.view.InflateException: Binary XML file line #23: Binary XML file line #23: Error inflating class fragment
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2817)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892)
    at android.app.ActivityThread.-wrap11(Unknown Source:0)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593)
    at android.os.Handler.dispatchMessage(Handler.java:105)
    at android.os.Looper.loop(Looper.java:164)
    at android.app.ActivityThread.main(ActivityThread.java:6541)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
 Caused by: android.view.InflateException: Binary XML file line #23: Binary XML file line #23: Error inflating class fragment
 Caused by: android.view.InflateException: Binary XML file line #23: Error inflating class fragment
 Caused by: java.lang.RuntimeException: Exception inflating com.example.mobileapp:navigation/mobile_navigation line 12
    at androidx.navigation.NavInflater.inflate(NavInflater.java:97)
    at androidx.navigation.NavController.setGraph(NavController.java:557)
    at androidx.navigation.NavController.setGraph(NavController.java:539)
    at androidx.navigation.fragment.NavHostFragment.onCreate(NavHostFragment.java:248)
    at androidx.fragment.app.Fragment.performCreate(Fragment.java:2981)
    at androidx.fragment.app.FragmentStateManager.create(FragmentStateManager.java:474)
    at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:257)
    at androidx.fragment.app.FragmentLayoutInflaterFactory.onCreateView(FragmentLayoutInflaterFactory.java:142)
    at androidx.fragment.app.FragmentController.onCreateView(FragmentController.java:135)
    at androidx.fragment.app.FragmentActivity.dispatchFragmentsOnCreateView(FragmentActivity.java:295)
    at androidx.fragment.app.FragmentActivity.onCreateView(FragmentActivity.java:274)
    at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:780)
    at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:730)
    at android.view.LayoutInflater.rInflate(LayoutInflater.java:863)
    at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:824)
    at android.view.LayoutInflater.inflate(LayoutInflater.java:515)
    at android.view.LayoutInflater.inflate(LayoutInflater.java:423)
    at android.view.LayoutInflater.inflate(LayoutInflater.java:374)
    at androidx.appcompat.app.AppCompatDelegateImpl.setContentView(AppCompatDelegateImpl.java:706)
    at androidx.appcompat.app.AppCompatActivity.setContentView(AppCompatActivity.java:195)
    at com.example.mobileapp.AccountMainActivity.onCreate(AccountMainActivity.java:32)
    at android.app.Activity.performCreate(Activity.java:6975)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1213)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2770)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892)
    at android.app.ActivityThread.-wrap11(Unknown Source:0)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593)
    at android.os.Handler.dispatchMessage(Handler.java:105)
    at android.os.Looper.loop(Looper.java:164)
    at android.app.ActivityThread.main(ActivityThread.java:6541)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
 Caused by: java.lang.IllegalStateException: Could not find Navigator with name "improved_fragment". You must call NavController.addNavigator() for each navigation type.
    at androidx.navigation.NavigatorProvider.getNavigator(NavigatorProvider.java:98)
    at androidx.navigation.NavInflater.inflate(NavInflater.java:107)
    at androidx.navigation.NavInflater.inflate(NavInflater.java:141)
    at androidx.navigation.NavInflater.inflate(NavInflater.java:88)
        ... 32 more

The main activity looks like this:

package com.example.mobileapp;

import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.navigation.NavController;
import androidx.navigation.Navigation;
import androidx.navigation.fragment.NavHostFragment;
import androidx.navigation.ui.AppBarConfiguration;
import androidx.navigation.ui.NavigationUI;

import com.example.mobileapp.databinding.AccountMainActivityBinding;
import com.example.mobileapp.ui.ImprovedFragmentNavigator;
import com.google.android.material.bottomnavigation.BottomNavigationView;
import com.google.android.material.navigation.NavigationBarView;

public class AccountMainActivity extends AppCompatActivity {

private Handler mHandler = new Handler();
private AccountMainActivityBinding binding;

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.account_main_activity);

    BottomNavigationView navView = findViewById(R.id.nav_view);
    AppBarConfiguration appBarConfiguration = new AppBarConfiguration.Builder(
            R.id.navigation_user, R.id.navigation_orders, R.id.navigation_products, R.id.navigation_companies, R.id.navigation_map)
            .build();
    NavHostFragment navHostFragment = (NavHostFragment) getSupportFragmentManager().findFragmentById(R.id.nav_host_fragment_activity_main);

    final NavController navController = navHostFragment.getNavController();
    navController.getNavigatorProvider().addNavigator(new ImprovedFragmentNavigator(this, navHostFragment.getChildFragmentManager(), R.id.nav_host_fragment_activity_main));
    navController.setGraph(R.navigation.mobile_navigation);

    NavigationUI.setupWithNavController(navView, navController);

    navView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
        @Override
        public boolean onNavigationItemSelected(@NonNull MenuItem item) {
            int id = item.getItemId();
            if (item.isChecked()) return false;

            switch (id)
            {
                case R.id.navigation_user :
                    navController.navigate(R.id.action_global_navigation_user);
                    break;
                case R.id.navigation_orders :
                    navController.navigate(R.id.action_global_navigation_orders);
                    break;
                case R.id.navigation_products :
                    navController.navigate(R.id.action_global_navigation_products);
                    break;
                case R.id.navigation_companies :
                    navController.navigate(R.id.action_global_navigation_companies);
                    break;
                case R.id.navigation_map :
                    navController.navigate(R.id.action_global_navigation_map);
                    break;
            }
            return true;
        }
    });
}
}

The main activity XML looks like this:

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".AccountMainActivity">

<fragment
    android:id="@+id/nav_host_fragment_activity_main"
    android:name="androidx.navigation.fragment.NavHostFragment"
    android:layout_width="match_parent"
    android:layout_height="0dp"
    app:defaultNavHost="true"
    app:layout_constraintBottom_toTopOf="@id/nav_view"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintVertical_bias="0.0"
    app:navGraph="@navigation/mobile_navigation" />

<com.google.android.material.bottomnavigation.BottomNavigationView
    android:id="@+id/nav_view"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:layout_below="@+id/nav_host_fragment_activity_main"
    android:background="?android:attr/windowBackground"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    app:menu="@menu/bottom_nav_menu" />

</androidx.constraintlayout.widget.ConstraintLayout>

The navigation file looks like this:

<?xml version="1.0" encoding="utf-8"?>
<navigation xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/mobile_navigation"
app:startDestination="@+id/navigation_user">

<improved_fragment
    android:id="@+id/navigation_user"
    android:name="com.example.mobileapp.ui.user.UserFragment"
    android:label="@string/title_user"
    tools:layout="@layout/fragment_user" />

<improved_fragment
    android:id="@+id/navigation_orders"
    android:name="com.example.mobileapp.ui.orders.OrdersFragment"
    android:label="@string/title_orders"
    tools:layout="@layout/fragment_orders" />

<improved_fragment
    android:id="@+id/navigation_products"
    android:name="com.example.mobileapp.ui.products.ProductsFragment"
    android:label="@string/title_products"
    tools:layout="@layout/fragment_products" />

<improved_fragment
    android:id="@+id/navigation_companies"
    android:name="com.example.mobileapp.ui.companies.CompaniesFragment"
    android:label="@string/title_companies"
    tools:layout="@layout/fragment_companies" />

<improved_fragment
    android:id="@+id/navigation_map"
    android:name="com.example.mobileapp.ui.map.MapFragment"
    android:label="@string/title_map"
    tools:layout="@layout/fragment_map" />

<action
    android:id="@+id/action_global_navigation_user"
    app:destination="@id/navigation_user"
    app:launchSingleTop="true"
    app:popUpTo="@id/navigation_user" />

<action
    android:id="@+id/action_global_navigation_orders"
    app:destination="@id/navigation_orders"
    app:launchSingleTop="true"
    app:popUpTo="@id/navigation_orders" />

<action
    android:id="@+id/action_global_navigation_products"
    app:destination="@id/navigation_products"
    app:launchSingleTop="true"
    app:popUpTo="@id/navigation_products" />

<action
    android:id="@+id/action_global_navigation_companies"
    app:destination="@id/navigation_companies"
    app:launchSingleTop="true"
    app:popUpTo="@id/navigation_companies" />

<action
    android:id="@+id/action_global_navigation_map"
    app:destination="@id/navigation_map"
    app:launchSingleTop="true"
    app:popUpTo="@id/navigation_map" />

</navigation>

And finally my fragment file looks like this:

package com.example.mobileapp.ui;

import android.annotation.SuppressLint;
import android.content.Context;
import android.content.res.TypedArray;
import android.os.Bundle;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;

import androidx.annotation.CallSuper;
import androidx.annotation.IdRes;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;
import androidx.fragment.app.FragmentTransaction;
import androidx.navigation.NavDestination;
import androidx.navigation.NavOptions;
import androidx.navigation.Navigator;
import androidx.navigation.NavigatorProvider;
import androidx.navigation.fragment.FragmentNavigator;

import com.example.mobileapp.R;

import java.util.ArrayDeque;
import java.util.Collections;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;

@Navigator.Name("improved_fragment")
public class ImprovedFragmentNavigator extends Navigator<ImprovedFragmentNavigator.Destination>{

private static final String TAG = "ImprovedFragmentNavigator";
private static final String KEY_BACK_STACK_IDS = "androidx-nav-fragment:navigator:backStackIds";

private final Context mContext;
@SuppressWarnings("WeakerAccess") /* synthetic access */
final FragmentManager mFragmentManager;
private final int mContainerId;
@SuppressWarnings("WeakerAccess") /* synthetic access */
        ArrayDeque<Integer> mBackStack = new ArrayDeque<>();
@SuppressWarnings("WeakerAccess") /* synthetic access */
        boolean mIsPendingBackStackOperation = false;

public ImprovedFragmentNavigator(@NonNull Context context, @NonNull FragmentManager manager,
                                 int containerId) {
    mContext = context;
    mFragmentManager = manager;
    mContainerId = containerId;
}

@Override
public boolean popBackStack() {
    if (mBackStack.isEmpty()) {
        return false;
    }
    if (mFragmentManager.isStateSaved()) {
        Log.i(TAG, "Ignoring popBackStack() call: FragmentManager has already"
                + " saved its state");
        return false;
    }
    if (mFragmentManager.getBackStackEntryCount() > 0) {
        mFragmentManager.popBackStack(
                generateBackStackName(mBackStack.size(), mBackStack.peekLast()),
                FragmentManager.POP_BACK_STACK_INCLUSIVE);
        mIsPendingBackStackOperation = true;
    } // else, we're on the first Fragment, so there's nothing to pop from FragmentManager
    mBackStack.removeLast();
    return true;
}

@NonNull
@Override
public ImprovedFragmentNavigator.Destination createDestination() {
    return new ImprovedFragmentNavigator.Destination(this);
}

@Deprecated
@NonNull
public Fragment instantiateFragment(@NonNull Context context,
                                    @NonNull FragmentManager fragmentManager,
                                    @NonNull String className, @SuppressWarnings("unused") @Nullable Bundle args) {
    return fragmentManager.getFragmentFactory().instantiate(
            context.getClassLoader(), className);
}

@Nullable
@Override
public NavDestination navigate(@NonNull Destination destination, @Nullable Bundle args,
                               @Nullable NavOptions navOptions, @Nullable Navigator.Extras navigatorExtras) {
    if (mFragmentManager.isStateSaved()) {
        Log.i(TAG, "Ignoring navigate() call: FragmentManager has already"
                + " saved its state");
        return null;
    }
    String className = destination.getClassName();
    if (className.charAt(0) == '.') {
        className = mContext.getPackageName() + className;
    }

    final FragmentTransaction ft = mFragmentManager.beginTransaction();

    int enterAnim = navOptions != null ? navOptions.getEnterAnim() : -1;
    int exitAnim = navOptions != null ? navOptions.getExitAnim() : -1;
    int popEnterAnim = navOptions != null ? navOptions.getPopEnterAnim() : -1;
    int popExitAnim = navOptions != null ? navOptions.getPopExitAnim() : -1;
    if (enterAnim != -1 || exitAnim != -1 || popEnterAnim != -1 || popExitAnim != -1) {
        enterAnim = enterAnim != -1 ? enterAnim : 0;
        exitAnim = exitAnim != -1 ? exitAnim : 0;
        popEnterAnim = popEnterAnim != -1 ? popEnterAnim : 0;
        popExitAnim = popExitAnim != -1 ? popExitAnim : 0;
        ft.setCustomAnimations(enterAnim, exitAnim, popEnterAnim, popExitAnim);
    }

    String tag = Integer.toString(destination.getId());
    Fragment primaryNavigationFragment = mFragmentManager.getPrimaryNavigationFragment();
    if(primaryNavigationFragment != null)
        ft.hide(primaryNavigationFragment);
    Fragment destinationFragment = mFragmentManager.findFragmentByTag(tag);
    if(destinationFragment == null) {
        destinationFragment = instantiateFragment(mContext, mFragmentManager, className, args);
        destinationFragment.setArguments(args);
        ft.add(mContainerId, destinationFragment , tag);
    }
    else
        ft.show(destinationFragment);

    ft.setPrimaryNavigationFragment(destinationFragment);

    final @IdRes int destId = destination.getId();
    final boolean initialNavigation = mBackStack.isEmpty();
    // TODO Build first class singleTop behavior for fragments
    final boolean isSingleTopReplacement = navOptions != null && !initialNavigation
            && navOptions.shouldLaunchSingleTop()
            && mBackStack.peekLast() == destId;

    boolean isAdded;
    if (initialNavigation) {
        isAdded = true;
    } else if (isSingleTopReplacement) {
        // Single Top means we only want one instance on the back stack
        if (mBackStack.size() > 1) {
            // If the Fragment to be replaced is on the FragmentManager's
            // back stack, a simple replace() isn't enough so we
            // remove it from the back stack and put our replacement
            // on the back stack in its place
            mFragmentManager.popBackStackImmediate(
                    generateBackStackName(mBackStack.size(), mBackStack.peekLast()), 0);
            mIsPendingBackStackOperation = false;
        }
        isAdded = false;
    } else {
        ft.addToBackStack(generateBackStackName(mBackStack.size() + 1, destId));
        mIsPendingBackStackOperation = true;
        isAdded = true;
    }
    if (navigatorExtras instanceof FragmentNavigator.Extras) {
        FragmentNavigator.Extras extras = (FragmentNavigator.Extras) navigatorExtras;
        for (Map.Entry<View, String> sharedElement : extras.getSharedElements().entrySet()) {
            ft.addSharedElement(sharedElement.getKey(), sharedElement.getValue());
        }
    }
    ft.setReorderingAllowed(true);
    ft.commit();
    // The commit succeeded, update our view of the world
    if (isAdded) {
        mBackStack.add(destId);
        return destination;
    } else {
        return null;
    }
}

@Override
@Nullable
public Bundle onSaveState() {
    Bundle b = new Bundle();
    int[] backStack = new int[mBackStack.size()];
    int index = 0;
    for (Integer id : mBackStack) {
        backStack[index++] = id;
    }
    b.putIntArray(KEY_BACK_STACK_IDS, backStack);
    return b;
}

@Override
public void onRestoreState(@Nullable Bundle savedState) {
    if (savedState != null) {
        int[] backStack = savedState.getIntArray(KEY_BACK_STACK_IDS);
        if (backStack != null) {
            mBackStack.clear();
            for (int destId : backStack) {
                mBackStack.add(destId);
            }
        }
    }
}

@NonNull
private String generateBackStackName(int backStackIndex, int destId) {
    return backStackIndex + "-" + destId;
}

private int getDestId(@Nullable String backStackName) {
    String[] split = backStackName != null ? backStackName.split("-") : new String[0];
    if (split.length != 2) {
        throw new IllegalStateException("Invalid back stack entry on the "
                + "NavHostFragment's back stack - use getChildFragmentManager() "
                + "if you need to do custom FragmentTransactions from within "
                + "Fragments created via your navigation graph.");
    }
    try {
        // Just make sure the backStackIndex is correctly formatted
        Integer.parseInt(split[0]);
        return Integer.parseInt(split[1]);
    } catch (NumberFormatException e) {
        throw new IllegalStateException("Invalid back stack entry on the "
                + "NavHostFragment's back stack - use getChildFragmentManager() "
                + "if you need to do custom FragmentTransactions from within "
                + "Fragments created via your navigation graph.");
    }
}

@SuppressWarnings("WeakerAccess") /* synthetic access */
boolean isBackStackEqual() {
    int fragmentBackStackCount = mFragmentManager.getBackStackEntryCount();
    // Initial fragment won't be on the FragmentManager's back stack so +1 its count.
    if (mBackStack.size() != fragmentBackStackCount + 1) {
        return false;
    }

    // From top to bottom verify destination ids match in both back stacks/
    Iterator<Integer> backStackIterator = mBackStack.descendingIterator();
    int fragmentBackStackIndex = fragmentBackStackCount - 1;
    while (backStackIterator.hasNext() && fragmentBackStackIndex >= 0) {
        int destId = backStackIterator.next();
        try {
            int fragmentDestId = getDestId(mFragmentManager
                    .getBackStackEntryAt(fragmentBackStackIndex--)
                    .getName());
            if (destId != fragmentDestId) {
                return false;
            }
        } catch (NumberFormatException e) {
            throw new IllegalStateException("Invalid back stack entry on the "
                    + "NavHostFragment's back stack - use getChildFragmentManager() "
                    + "if you need to do custom FragmentTransactions from within "
                    + "Fragments created via your navigation graph.");
        }
    }

    return true;
}

@NavDestination.ClassType(Fragment.class)
public static class Destination extends NavDestination {

    private String mClassName;

    public Destination(@NonNull NavigatorProvider navigatorProvider) {
        this(navigatorProvider.getNavigator(ImprovedFragmentNavigator.class));
    }

    public Destination(@NonNull Navigator<? extends ImprovedFragmentNavigator.Destination> fragmentNavigator) {
        super(fragmentNavigator);
    }

    @CallSuper
    @Override
    public void onInflate(@NonNull Context context, @NonNull AttributeSet attrs) {
        super.onInflate(context, attrs);
        TypedArray a = context.getResources().obtainAttributes(attrs,
                R.styleable.FragmentNavigator);
        String className = a.getString(R.styleable.FragmentNavigator_android_name);
        if (className != null) {
            setClassName(className);
        }
        a.recycle();
    }

    @NonNull
    public final ImprovedFragmentNavigator.Destination setClassName(@NonNull String className) {
        mClassName = className;
        return this;
    }

    @NonNull
    public final String getClassName() {
        if (mClassName == null) {
            throw new IllegalStateException("Fragment class was not set");
        }
        return mClassName;
    }

    @NonNull
    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append(super.toString());
        sb.append(" class=");
        if (mClassName == null) {
            sb.append("null");
        } else {
            sb.append(mClassName);
        }
        return sb.toString();
    }
}

public static final class Extras implements Navigator.Extras {
    private final LinkedHashMap<View, String> mSharedElements = new LinkedHashMap<>();

    Extras(Map<View, String> sharedElements) {
        mSharedElements.putAll(sharedElements);
    }

    @NonNull
    public Map<View, String> getSharedElements() {
        return Collections.unmodifiableMap(mSharedElements);
    }

    public static final class Builder {
        private final LinkedHashMap<View, String> mSharedElements = new LinkedHashMap<>();

        @NonNull
        public ImprovedFragmentNavigator.Extras.Builder addSharedElements(@NonNull Map<View, String> sharedElements) {
            for (Map.Entry<View, String> sharedElement : sharedElements.entrySet()) {
                View view = sharedElement.getKey();
                String name = sharedElement.getValue();
                if (view != null && name != null) {
                    addSharedElement(view, name);
                }
            }
            return this;
        }

        @NonNull
        public ImprovedFragmentNavigator.Extras.Builder addSharedElement(@NonNull View sharedElement, @NonNull String name) {
            mSharedElements.put(sharedElement, name);
            return this;
        }

        @NonNull
        public ImprovedFragmentNavigator.Extras build() {
            return new ImprovedFragmentNavigator.Extras(mSharedElements);
        }
    }
}
}

>Solution :

As per the documentation:

Caution: When manually calling setGraph(), note the following:

• Don’t use the app:navGraph element when adding the NavHostFragment in XML.
• Don’t call NavHostFragment.create(@NavigationRes int).
• Don’t use any other APIs that rely solely on the R.navigation ID to inflate and set your graph.

So just remove your app:navGraph attribute from your XML file to only set your graph via setGraph after your addition of your custom Navigator.