Question

我正在使用the following example中的BottomNavigationDrawer / BottomSheetDialog

我在主Activity中运行了三个片段，我在使用FragmentTransactions和SupportFragmentManager之间进行导航。

FragmentRevivIncidentDashboard

@Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.fragment_reviv_incident_dashboard, container, false);

        setRetainInstance(true);

        // initialize variables

        email = ((Reviv) getActivity()).getEmail();
        apikey = ((Reviv) getActivity()).getApikey();

        // set up UI elements

        menuButton = ((Reviv)getActivity()).getFab();
                    menuButton.setImageResource(R.drawable.add_white);
        bottomAppBar = ((Reviv)getActivity()).getBottom_app_bar();
        bottomAppBar.setFabAlignmentMode(BottomAppBar.FAB_ALIGNMENT_MODE_CENTER);
        navigationView = ((Reviv) getActivity()).getNavigationView();

FragmentSettingsMain

@Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view = inflater.inflate (R.layout.fragment_revive_settings, container, false);
        ((Reviv) getActivity()).getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        setRetainInstance(true);

        // Activity Views and viewModel
        bottomAppBar = ((Reviv)getActivity()).getBottom_app_bar();
        bottomAppBar.setFabAlignmentMode(BottomAppBar.FAB_ALIGNMENT_MODE_END);
        navigationView = ((Reviv) getActivity()).getNavigationView();
        if(navigationView == null) navigationView = ((Reviv) getActivity()).getNavigationView();


        menuButton = ((Reviv)getActivity()).getFab();
        menuButton.setImageResource(R.drawable.baseline_undo_white_24dp);
        menuButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if(navigationView == null) navigationView = ((Reviv) getActivity()).getNavigationView();
                navigationView.getMenu().findItem(R.id.app_bar_incident).setChecked(true);

                ((Reviv) getActivity()).getSupportFragmentManager()
                        .beginTransaction()
                        .replace(R.id.containerFrameLayout, new FragmentRevivIncidentDashboard()).commit();
            }
        });

活动-Reviv.class

BottomNavigationDrawerFragment fragment;

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_reviv);
        uberLayout = findViewById(R.id.uberLayout);
        floatingActionButton = findViewById(R.id.floatingActionButton);

        // Initialize all the location related objects here

        if (ContextCompat.checkSelfPermission(this,
                android.Manifest.permission.INTERNET)
                != PackageManager.PERMISSION_GRANTED) {

            ActivityCompat.requestPermissions(this,
                    new String[]{android.Manifest.permission.INTERNET},
                    MY_PERMISSIONS_ACCESS_INTERNET);
        }

        // ask for permissions
        displayLocationSettingsRequest(getApplicationContext());
        beingLocationUpdation(this);


        bottom_app_bar = findViewById(R.id.bottom_app_bar);
        setSupportActionBar(bottom_app_bar);
        fragment = new BottomNavigationDrawerFragment();
        navigationView = fragment.getNavigationView();

*Elsewhere in the main Activity*

public NavigationView getNavigationView() {
        if(fragment == null) {
            fragment = new BottomNavigationDrawerFragment();
            navigationView = fragment.getNavigationView();
        } else navigationView = fragment.getNavigationView();
        return navigationView;
    }

底页片段

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.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/bottomsheet_menu"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:alpha="1">

    <android.support.constraint.ConstraintLayout
        android:id="@+id/constraintLayout"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@color/colorPrimary"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">

        <TextView
            android:id="@+id/txtUsername"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginBottom="8dp"
            android:layout_marginStart="8dp"
            android:layout_marginTop="4dp"
            android:text="User Name"
            android:textAppearance="@style/TextAppearance.AppCompat.Medium"
            android:textColor="@color/label_text_light"
            android:textSize="14sp"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintStart_toEndOf="@+id/imageView4"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintVertical_bias="0.3" />

        <ImageView
            android:id="@+id/imageView4"
            android:layout_width="63dp"
            android:layout_height="65dp"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            app:srcCompat="@drawable/baseline_face_white_48" />

        <TextView
            android:id="@+id/txtEmail"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginBottom="8dp"
            android:text="Email Address"
            android:textColor="@color/colorText"
            android:textSize="10sp"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintStart_toStartOf="@+id/txtUsername"
            app:layout_constraintTop_toBottomOf="@+id/txtUsername"
            app:layout_constraintVertical_bias="0.0" />

        <ImageView
            android:id="@+id/imgClose"
            android:layout_width="24dp"
            android:layout_height="24dp"
            android:layout_marginBottom="8dp"
            android:layout_marginEnd="16dp"
            android:layout_marginTop="8dp"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            app:srcCompat="@drawable/baseline_close_white_48dp" />

    </android.support.constraint.ConstraintLayout>

    <android.support.design.widget.NavigationView
        android:id="@+id/navigation_view"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom"
        app:itemTextAppearance="@style/TextAppearance.AppCompat.Body2"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/constraintLayout"
        app:itemIconTint="@color/drawer_item"
        app:itemTextColor="@color/drawer_item"
        app:itemBackground="@drawable/menu_background_color"
        app:menu="@menu/bottom_nav_drawer_menu">

    </android.support.design.widget.NavigationView>

</android.support.constraint.ConstraintLayout>

问题

当我使用该按钮从“设置片段”中导航回默认（第一个）片段时，菜单不会更新。

尝试从片段中获取对Main活动中定义的navigationView的引用，这给了我NPE，然后调用

menuButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if(navigationView == null) navigationView = ((Reviv) getActivity()).getNavigationView();
            navigationView.getMenu().findItem(R.id.app_bar_incident).setChecked(true);

            ((Reviv) getActivity()).getSupportFragmentManager()
                    .beginTransaction()
                    .replace(R.id.containerFrameLayout, new FragmentRevivIncidentDashboard()).commit();
        }
    });

不会导致任何可见变化，即使正在显示IncidentDashboard片段，“设置”菜单项也会保持选中状态。

甚至

menuButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if(navigationView == null) navigationView = ((Reviv) getActivity()).getNavigationView();
                navigationView.getMenu().findItem(R.id.app_bar_incident).setChecked(true);
                Menu bottomNavigationMenu = navigationView.getMenu();
                bottomNavigationMenu.performIdentifierAction(R.id.app_bar_incident, 0);
                /*navigationView.setCheckedItem(R.id.default);*/
                /*((Reviv) getActivity()).getSupportFragmentManager()
                        .beginTransaction()
                        .replace(R.id.containerFrameLayout, new FragmentRevivIncidentDashboard()).commit();*/
            }
        });

在第二种情况下导致NPE，在第一种情况下没有可见的菜单选择。

java.lang.NullPointerException：尝试调用虚拟方法 'android.support.v4.app.FragmentManager android.support.v4.app.FragmentActivity.getSupportFragmentManager（）' 在空对象引用上

设置

navigationView.setCheckedItem(R.id.app_bar_incident);

目标（事件仪表板）中的

片段会在navigationView上生成NPE。

由于：java.lang.NullPointerException：尝试调用虚拟方法“无效” android.support.design.widget.NavigationView.setCheckedItem（int）' 空对象引用在com.package.class.Fragments.FragmentRevivIncidentDashboard.onCreateView（FragmentRevivIncidentDashboard.java:130）

我见过this SO question和this one，但它们似乎没有帮助。

如何从片段主菜单中选择导航菜单项？

[UPDATE]同样在THIS ANSWER上找到了KeepassXC's source code，但尽管感觉像是正确的，但它不起作用。

无法为片段中的导航抽屉中的正确项目设置颜色/背景选择

0 个答案: