带有片段的片段中的TabLayout

Question

通过滑动TabLayout即可更改Fragment布局，但单击此选项卡不会更改。 我的应用程序上的MainActivity通过onNavigationItemSelected更改了带有TestFragment的Fragment，从而正确显示了布局；但是TabLayout中的Tab不可点击。为什么？

TestFragment.java

ViewPager mViewPager;
TabLayout tabLayout;
private SectionsPagerAdapter mSectionsPagerAdapter;

@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.fragment_test, container, false);
    mViewPager = view.findViewById(R.id.container);
    tabLayout = view.findViewById(R.id.tabs);
    mSectionsPagerAdapter = new SectionsPagerAdapter(getChildFragmentManager());
    mViewPager.setAdapter(mSectionsPagerAdapter);
    tabLayout.setupWithViewPager(mViewPager);
    mViewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
    tabLayout.addOnTabSelectedListener(new TabLayout.ViewPagerOnTabSelectedListener(mViewPager));
    return view;
}


public static class PlaceholderFragment extends Fragment {

    public PlaceholderFragment() {
    }

    public static PlaceholderFragment newInstance(int sectionNumber) {
        PlaceholderFragment fragment = new PlaceholderFragment();
        Bundle args = new Bundle();
        args.putInt("section", sectionNumber);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        int tab = getArguments().getInt("section");
        View rootView = inflater.inflate(R.layout.fragment_main, container, false);
        TextView textView = rootView.findViewById(R.id.section_label);
        if(tab == 1) textView.setText("Tab 1 test");
        if(tab == 2) textView.setText("Tab 2 test");
        return rootView;
    }
}

public class SectionsPagerAdapter extends FragmentPagerAdapter {

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

    @Override
    public Fragment getItem(int position) {
        return PlaceholderFragment.newInstance(position + 1);
    }

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

fragmentTest.xml

<FrameLayout 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.support.design.widget.CoordinatorLayout
    android:id="@+id/main_contents"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <android.support.design.widget.AppBarLayout
        android:id="@+id/appbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

    <android.support.design.widget.TabLayout
        android:id="@+id/tabs"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@color/colorPrimary"
        android:minHeight="?attr/actionBarSize"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
        app:tabIndicatorColor="@color/white"
        app:tabIndicatorHeight="2.5dp"
        app:tabSelectedTextColor="@color/white"
        app:tabTextColor="@color/black_overlay" >

        <android.support.design.widget.TabItem
            android:id="@+id/tabItem"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Tab 1" />

        <android.support.design.widget.TabItem
            android:id="@+id/tabItem2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Tab 2" />
    </android.support.design.widget.TabLayout>

    </android.support.design.widget.AppBarLayout>
</android.support.design.widget.CoordinatorLayout>

<android.support.v4.view.ViewPager
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior" />

具有滑动更改布局的选项卡1和选项卡2，但是在选项卡上的onClick时，它们不会更改。 谢谢。