Android使用BottomNavigationView+NavigationUI报错

Android Studio版本：

Android Studio Bumblebee | 2021.1.1 Patch 2
Build #AI-211.7628.21.2111.8193401, built on February 17, 2022
Runtime version: 11.0.11+9-b60-7590822 amd64
VM: OpenJDK 64-Bit Server VM by Oracle Corporation
Windows 10 10.0
GC: G1 Young Generation, G1 Old Generation
Memory: 1280M
Cores: 6
Registry: external.system.auto.import.disabled=true, vcs.annotations.preload=true, ide.balloon.shadow.size=0
Non-Bundled Plugins: GLSL (1.20), com.alayouni.ansiHighlight (1.2.4), com.intellij.ideolog (203.0.27.0), GsonFormatPlus (1.6.1), GsonOrXmlFormat (2.0), com.github.setial (4.0.2), com.intuit.intellij.makefile (1.0.16), com.jetbrains.annotations.preloader (1.0.3), com.markskelton.one-dark-theme (5.5.1), de.longnguyen.plugin.clion.new.entry.point.plugin (1.3), Dart (211.7808), io.flutter (64.1.2), com.developerphil.adbidea (1.6.1), com.mistamek.drawablepreview.drawable-preview (1.1.5), com.likfe.ideaplugin.eventbus3 (2020.0.2), org.intellij.plugins.markdown (211.7142.37)

使用场景

public class MainActivity extends AppCompatActivity {
private ActivityMainBinding binding;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
     binding = ActivityMainBinding.inflate(getLayoutInflater());
     setContentView(binding.getRoot());
        BottomNavigationView navView = findViewById(R.id.nav_view);
        // Passing each menu ID as a set of Ids because each
        // menu should be considered as top level destinations.
        AppBarConfiguration appBarConfiguration = new AppBarConfiguration.Builder(
                R.id.navigation_home, R.id.navigation_dashboard, R.id.navigation_notifications)
                .build();
        NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment_activity_main);
        NavigationUI.setupActionBarWithNavController(MainActivity.this, navController, appBarConfiguration);
        NavigationUI.setupWithNavController(binding.navView, navController);
    }
}

报错：

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.mz.demo/com.mz.demo.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.appcompat.app.ActionBar.setTitle(java.lang.CharSequence)' on a null object reference
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3639)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3796)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:103)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2214)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loopOnce(Looper.java:201)
        at android.os.Looper.loop(Looper.java:288)
        at android.app.ActivityThread.main(ActivityThread.java:7842)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:548)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1003)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.appcompat.app.ActionBar.setTitle(java.lang.CharSequence)' on a null object reference
        at androidx.navigation.ui.ActionBarOnDestinationChangedListener.setTitle(ActionBarOnDestinationChangedListener.java:48)
        at androidx.navigation.ui.AbstractAppBarOnDestinationChangedListener.onDestinationChanged(AbstractAppBarOnDestinationChangedListener.java:103)
        at androidx.navigation.NavController.addOnDestinationChangedListener(NavController.java:233)
        at androidx.navigation.ui.NavigationUI.setupActionBarWithNavController(NavigationUI.java:237)
        at com.mz.demo.MainActivity.onCreate(MainActivity.java:33)
        at android.app.Activity.performCreate(Activity.java:8051)
        at android.app.Activity.performCreate(Activity.java:8031)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1329)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3612)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3796) 
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:103) 
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2214) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loopOnce(Looper.java:201) 
        at android.os.Looper.loop(Looper.java:288) 
        at android.app.ActivityThread.main(ActivityThread.java:7842) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:548) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1003) 

跟踪错误：

public static void setupActionBarWithNavController(@NonNull AppCompatActivity activit
        @NonNull NavController navController,
        @NonNull AppBarConfiguration configuration) {
    navController.addOnDestinationChangedListener(
            new ActionBarOnDestinationChangedListener(activity, configuration));
}

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);
}

@Override
public void onDestinationChanged(@NonNull NavController controller,
        @NonNull NavDestination destination, @Nullable Bundle arguments) {
    if (destination instanceof FloatingWindow) {
        return;
    }
    Openable openableLayout = mOpenableLayoutWeakReference != null
            ? mOpenableLayoutWeakReference.get()
            : null;
    if (mOpenableLayoutWeakReference != null && openableLayout == null) {
        controller.removeOnDestinationChangedListener(this);
        return;
    }
    CharSequence label = destination.getLabel();
    if (label != null) {
        // Fill in the data pattern with the args to build a valid URI
        StringBuffer title = new StringBuffer();
        Pattern fillInPattern = Pattern.compile("\\{(.+?)\\}");
        Matcher matcher = fillInPattern.matcher(label);
        while (matcher.find()) {
            String argName = matcher.group(1);
            if (arguments != null && arguments.containsKey(argName)) {
                matcher.appendReplacement(title, "");
                //noinspection ConstantConditions
                title.append(arguments.get(argName).toString());
            } else {
                throw new IllegalArgumentException("Could not find " + argName + " in "
                        + arguments + " to fill label " + label);
            }
        }
        matcher.appendTail(title);
        setTitle(title);
    }
    boolean isTopLevelDestination = NavigationUI.matchDestinations(destination,
            mTopLevelDestinations);
    if (openableLayout == null && isTopLevelDestination) {
        setNavigationIcon(null, 0);
    } else {
        setActionBarUpIndicator(openableLayout != null && isTopLevelDestination);
    }
}

@Override
protected void setTitle(CharSequence title) {
    ActionBar actionBar = mActivity.getSupportActionBar();
    actionBar.setTitle(title);
}

这里

ActionBar actionBar = mActivity.getSupportActionBar();

获取到的actionBar==null导致问题出现

出现问题的根本 原因是设置的主题

 

 换成有ActionBar的主题就行了