为什么我的 android 选项卡布局不起作用？

Question

我正在尝试为我的应用创建一个标签滑动活动，但我无法找到问题所在。

这是标签活动的代码：

public class TabActivity extends AppCompatActivity {

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

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

    ViewPager viewPager = findViewById(R.id.container);
    viewPager.setAdapter(new SectionsPagerAdapter(getSupportFragmentManager()));
    TabLayout tabLayout = findViewById(R.id.tabs);
    viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
    tabLayout.addOnTabSelectedListener(new TabLayout.ViewPagerOnTabSelectedListener(viewPager));
}


@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_tab, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    int id = item.getItemId();

    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}

public static abstract class LayoutFragment extends Fragment {
    private final int layout;

    public LayoutFragment(@LayoutRes int layout) {
        this.layout = layout;
    }

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

    @RequiresApi(api = Build.VERSION_CODES.KITKAT)
    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
    }
}

public static class Fragment1 extends LayoutFragment {
    public Fragment1() {
        super(R.layout.fragment_one);
    }
}

public static class Fragment2 extends Fragment {
    public Fragment2() {
        super(R.layout.fragment_two);
    }
}

public class SectionsPagerAdapter extends FragmentPagerAdapter {

    SectionsPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int position) {
        // getItem is called to instantiate the fragment for the given page.
        switch (position) {
            case 0:
                return new Fragment1();
            default:
                return new Fragment2();
        }
    }

    @Override
    public int getCount() {
        return 2;
    }
}
}

代码正在完美编译，但片段 1 和片段 2 的选项卡根本没有出现。

我无法弄清楚出了什么问题以及哪里出了问题，我将不胜感激。

编辑：

这是我的 XML 代码：

<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout   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/main_content"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@drawable/wallpaper"
android:fitsSystemWindows="true"
tools:context=".TabActivity">

<com.google.android.material.appbar.AppBarLayout
    android:id="@+id/appbar"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:paddingTop="@dimen/appbar_padding_top"
    android:theme="@style/AppTheme.AppBarOverlay">

    <androidx.appcompat.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        android:layout_weight="1"
        android:background="?attr/colorPrimary"
        app:layout_scrollFlags="scroll|enterAlways"
        app:popupTheme="@style/AppTheme.PopupOverlay"
        app:title="@string/app_name">

    </androidx.appcompat.widget.Toolbar>

    <com.google.android.material.tabs.TabLayout
        android:id="@+id/tabs"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <com.google.android.material.tabs.TabItem
            android:id="@+id/tabItem"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/tab1" />

        <com.google.android.material.tabs.TabItem
            android:id="@+id/tabItem2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/tab2" />

    </com.google.android.material.tabs.TabLayout>
</com.google.android.material.appbar.AppBarLayout>

<androidx.viewpager.widget.ViewPager
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior" />

Answer 1

我认为您忘记设置带有标签的视图寻呼机试试这个。

ViewPager viewPager = findViewById(R.id.container);
viewPager.setAdapter(new SectionsPagerAdapter(getSupportFragmentManager()));
TabLayout tabLayout = findViewById(R.id.tabs);
tablayout.setUpWithViewPager(viewPager);

Answer 2

试试这个

tabLayout.setupWithViewPager(viewPager);

并删除这些行

viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
tabLayout.addOnTabSelectedListener(new TabLayout.ViewPagerOnTabSelectedListener(viewPager));

编辑

尝试使用LinearLayout 而不是android.support.design.widget.CoordinatorLayout

编辑

试试这个

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical">


    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <android.support.design.widget.TabLayout
            android:id="@+id/tabs"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="@color/tab_bg"
            app:tabGravity="fill"
            app:tabIndicatorHeight="2dp"
            app:tabMode="fixed" />
    </android.support.design.widget.AppBarLayout>

    <View
        android:layout_width="match_parent"
        android:layout_height="1dp"
        android:background="@color/colorAccent" />

    <android.support.v4.view.ViewPager
        android:id="@+id/viewpager"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        app:layout_behavior="@string/appbar_scrolling_view_behavior" />
</LinearLayout>

在活动中这样做

private void init(){
            ViewPager viewPager = v.findViewById(R.id.viewpager);
            setupViewPager(viewPager);
            TabLayout tabLayout = v.findViewById(R.id.tabs);
            tabLayout.setupWithViewPager(viewPager);
            tabLayout.setTabMode(TabLayout.MODE_FIXED);
            tabLayout.setTabGravity(TabLayout.GRAVITY_FILL);
    

            TextView tab1 = (TextView) ((LayoutInflater) getActivity().getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.custom_tab, null, false);

            TextView tab2 = (TextView) ((LayoutInflater) getActivity().getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.custom_tab, null, false);

            tabLayout.getTabAt(0).setCustomView(tab1);
            tabLayout.getTabAt(1).setCustomView(tab2);

}

     private void setupViewPager(final ViewPager viewPager) {
            ViewPagerAdapter viewPagerAdapter = new ViewPagerAdapter(getChildFragmentManager());

            viewPager.setOffscreenPageLimit(3);
            viewPager.setAdapter(viewPagerAdapter);
    }

  public class ViewPagerAdapter extends FragmentPagerAdapter {
      public ViewPagerAdapter(FragmentManager fragmentManager) {
          super(fragmentManager);
      }
  
      @Override
      public Fragment getItem(int position) {
          if(position == 0) return new Fragment1();
          if(position == 1) return new Fragment2();

          throw new IllegalStateException("Unexpected position " + position);
      }
  
      @Override
      public int getCount() {
          return 2;
      }
  
      @Override
      public CharSequence getPageTitle(int position) {
          if(position == 0) return "Fragment 1";
          if(position == 1) return "Fragment 2";
        
          throw new IllegalStateException("Unexpected position " + position);
      }
  }

这里是custom_tab.xml

<?xml version="1.0" encoding="utf-8"?>
    <TextView
            android:id="@+id/text1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" />