Почему не работает макет моей вкладки для Android?

Question

Я пытаюсь сделать скольжение по вкладкам для своего приложения, но не могу найти, что происходит не так.

Вот код активности вкладки:

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;
    }
}
}

Код компилируется отлично, но вкладки для фрагмента 1 и фрагмента 2 вообще не отображаются.

Я не могу понять, что происходит и где, я был бы признателен за любую помощь.

Edit:

Вот мой XML-код:

<?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

Я думаю, вы забыли настроить пейджер просмотра с вкладками, попробуйте этот.

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

Answer 2

попробуйте

tabLayout.setupWithViewPager(viewPager);

и удалите эту строку

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

EDIT

попробуйте использовать LinearLayout вместо android.support.design.widget.CoordinatorLayout

EDIT

попробуйте это

<?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>

и в действии сделать это

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());

            Fragment fragment1 = new Fragment();

            Fragment fragment2 = new Fragment();


            viewPagerAdapter.addFragment(fragment1, "title1");
            viewPagerAdapter.addFragment(fragment2, "title2");

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

 class ViewPagerAdapter extends FragmentPagerAdapter {
        private final List<Fragment> mFragmentList = new ArrayList<>();
        private final List<String> mFragmentTitleList = new ArrayList<>();

        ViewPagerAdapter(FragmentManager manager) {
            super(manager);
        }

        @Override
        public Fragment getItem(int position) {
            return mFragmentList.get(position);
        }

        @Override
        public int getCount() {
            return mFragmentList.size();
        }

        void addFragment(Fragment fragment, String title) {
            mFragmentList.add(fragment);
            mFragmentTitleList.add(title);
        }

        @Override
        public CharSequence getPageTitle(int position) {
            return mFragmentTitleList.get(position);
        }
    }

здесь 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" />