android 片段没有出现在抽屉旁边

Question

为什么我的 WelcomeFragment 没有出现在我的 main_container 中，我得到的只是一个绿屏，如下图所示：

我的代码：

主要活动

public class MainActivity extends AppCompatActivity implements WelcomeFragment.ArrowBtnListener
    , SetupAccountFragment.BtnOkListener {

FragmentManager fm;
private DrawerLayout drawer;


// for account setup fragment
@Override
public void btnOkMethod() {
    FoodListFragment foodListFragment = new FoodListFragment();

    fm.beginTransaction()
            .replace(R.id.main_container, foodListFragment)
            .commit();

}
// for account setup fragment


// for welcome fragment
@Override
public void lockDrawer() {
    drawer.setDrawerLockMode(DrawerLayout.LOCK_MODE_LOCKED_CLOSED);
}

@Override
public void unlockDrawer() {
    drawer.setDrawerLockMode(DrawerLayout.LOCK_MODE_UNLOCKED);
}

@Override
public void onArrowClick() {

    SetupAccountFragment setupAccountFragment = new SetupAccountFragment();

    fm.beginTransaction()
            .replace(R.id.main_container, setupAccountFragment)
            .addToBackStack(null)
            .commit();
}


// for welcome fragment


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

    Toolbar toolbar = findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);


    drawer = findViewById(R.id.drawer_layout);

    ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(this, drawer, toolbar,
            R.string.drawer_open, R.string.drawer_close);

    drawer.addDrawerListener(toggle);
    toggle.syncState();


    fm = getSupportFragmentManager();

    FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
    fragmentTransaction.replace(R.id.drawer_fragment_container, new DrawerListFragment());
    fragmentTransaction.commit();

    Fragment fragment = fm.findFragmentById(R.id.main_container);

    if (fragment == null) {
        // adding fragment to main container
        fragment = new WelcomeFragment();

        fm.beginTransaction()
                .replace(R.id.main_container, fragment)
                .addToBackStack(null)
                .commit();
    }


}

// make back button close navigation drawer
@Override
public void onBackPressed() {
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START);
    } else {
        super.onBackPressed();
    }

}

}

activity_main

<androidx.drawerlayout.widget.DrawerLayout 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/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:context=".MainActivity"
tools:openDrawer="start">


<androidx.appcompat.widget.Toolbar
    android:id="@+id/toolbar"
    android:layout_width="match_parent"
    android:layout_height="?attr/actionBarSize"
    android:background="@color/colorPrimary"
    android:elevation="4dp"
    android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
    app:popupTheme="@style/ThemeOverlay.AppCompat.Light" />


<FrameLayout
    android:id="@+id/main_container"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />


<FrameLayout
    android:id="@+id/drawer_fragment_container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_gravity="start"
    android:fitsSystemWindows="true" />

欢迎片段

public class WelcomeFragment 扩展片段 {

private static final String TAG = "WelcomeFragment";
private Button btnArrow;

interface ArrowBtnListener {
    void onArrowClick();
    void lockDrawer();
   void unlockDrawer();
}

private ArrowBtnListener arrowBtnListener;

@Override
public void onAttach(@NonNull Context context) {
    super.onAttach(context);
    try {
        arrowBtnListener = (ArrowBtnListener) context;
    } catch (ClassCastException e) {
        Log.d(TAG, "onAttach: " + e.getMessage());
    }
}

public WelcomeFragment() {
    // Required empty public constructor
}


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    //arrowBtnListener.lockDrawer();
    return inflater.inflate(R.layout.fragment_welcome, container, false);
}

@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);
    btnArrow = view.findViewById(R.id.welcome_frag_btn_arrow);

}

@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    btnArrow.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            arrowBtnListener.onArrowClick();
        }
    });
}
}

fragment_welcome

<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=".WelcomeFragment">

<ImageView
    android:id="@+id/imageView"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:adjustViewBounds="true"
    android:background="@drawable/image_welcome"
    android:scaleType="fitXY"
    tools:layout_editor_absoluteX="0dp"
    tools:layout_editor_absoluteY="0dp" />

<ImageView
    android:id="@+id/imageView2"
    android:layout_width="180dp"
    android:layout_height="131dp"
    android:layout_marginTop="180dp"
    android:background="@mipmap/ic_launcher"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="@+id/imageView" />

<TextView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginTop="20dp"
    android:text="restaurant name"
    android:textAlignment="center"
    android:textColor="#860707"
    android:textSize="36sp"
    android:textStyle="bold"
    app:layout_constraintTop_toBottomOf="@+id/imageView2"
    tools:layout_editor_absoluteX="16dp" />

<Button
    android:id="@+id/welcome_frag_btn_arrow"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginEnd="16dp"
    android:layout_marginBottom="16dp"
    android:background="@drawable/welcome_arrow"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent" />

Answer 1

像下面这样更改您的activity_main.xml：

<androidx.drawerlayout.widget.DrawerLayout 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/drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:context=".MainActivity"
    tools:openDrawer="start">


    <LinearLayout
        android:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="match_parent" >
        <androidx.appcompat.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="@color/colorPrimary"
            android:elevation="4dp"
            android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
            app:popupTheme="@style/ThemeOverlay.AppCompat.Light" />


        <FrameLayout
            android:id="@+id/main_container"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />
    </LinearLayout>



    <FrameLayout
        android:id="@+id/drawer_fragment_container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:fitsSystemWindows="true" />

</androidx.drawerlayout.widget.DrawerLayout>

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