java - 将底部导航 Activity 转换为 Fragment

Question

我尝试使用 android 底部导航 Activity 作为 fragment ，但 Android Studio 3.5 使用新的 NavController 和 NavigationUI，这让我很难弄清楚它是如何工作的并返回运行时错误。

public class BottomFragment extends Fragment {

Activity activity;

public BottomFragment(Activity activity) {
    this.activity = activity;
}


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    View root = inflater.inflate(R.layout.activity_bottom_fragment, container, false);
    BottomNavigationView navView =  root.findViewById(R.id.nav_view);

    AppBarConfiguration appBarConfiguration = new AppBarConfiguration.Builder(
            R.id.navigation_home, R.id.navigation_dashboard, R.id.navigation_notifications)
            .build();

    NavController navController = Navigation.findNavController(activity, R.id.nav_host_fragment);//error here
    NavigationUI.setupActionBarWithNavController((AppCompatActivity) activity, navController, appBarConfiguration);
    NavigationUI.setupWithNavController(navView, navController);


    return root;
}}

主类

public class MainActivity extends AppCompatActivity {

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


    getSupportFragmentManager().beginTransaction()
            .replace(R.id.mainContainer,new BottomFragment(this)).commit();
}

主要 Activity 布局

<?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:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <FrameLayout
        android:id="@+id/mainContainer"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

运行时错误

java.lang.IllegalArgumentException: ID does not reference a View inside this Activity
    at android.app.Activity.requireViewById(Activity.java:2678)
    at androidx.core.app.ActivityCompat.requireViewById(ActivityCompat.java:363)
    at androidx.navigation.Navigation.findNavController(Navigation.java:58)
    at com.h_byk.test000.BottomFragment.onCreateView(BottomFragment.java:36)

Answer 1

您应该将公共(public) View onCreateView 中的一些代码放置到 onActivityCreated 函数中。

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                     Bundle savedInstanceState) {
    View root = inflater.inflate(R.layout.activity_bottom_fragment, container, false);
    return root;
}

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);

    BottomNavigationView navView =  root.findViewById(R.id.nav_view);

    AppBarConfiguration appBarConfiguration = new AppBarConfiguration.Builder(
        R.id.navigation_home, R.id.navigation_dashboard, R.id.navigation_notifications)
        .build();

    NavController navController = Navigation.findNavController(activity, R.id.nav_host_fragment);//error here
    NavigationUI.setupActionBarWithNavController((AppCompatActivity) activity, navController, appBarConfiguration);
    NavigationUI.setupWithNavController(navView, navController);
}

试试这个。无论如何，您不应该避免使用新的谷歌导航组件，请尝试遵循谷歌文档。阅读 this .