BottomNavigationView中的TabLayout隐藏数据，但两次滑动（在TabLayout中）后，数据出现

Question

我在底部使用BottomNavigationView创建了一个活动。 bottomnavigationview的第二个选项卡包含TabLayout（一周中的某几天）。 但是有一些奇怪的错误。当我运行应用程序时，没关系，然后我进入了带有tablayout的第二个选项卡，没关系，然后我又回到了第一个选项卡（第四张图片-好像应该这样），没关系，然后我转到了第二个标签，它是空的。但是，如果我要滑动（在TabLayout中第二天和第二天），那一天的数据就会出现。而且打开TabLayout中的哪个标签都没有关系，您总是应该两次滑动（向后或向后）此标签才会出现 例如，我在第二个选项卡上。我刷卡3（现在为空），我刷卡4（它已经不为空）。然后回到3（空），回到2（非空）。因此，如果我想显示3，则应该将其滑动到5或1。我做错了什么？

这是我在 activity_main.xml

中添加bottomNavigationView的方式

<android.support.design.widget.BottomNavigationView
    android:id="@+id/bottom_navigation"
    android:layout_width="match_parent"
    android:layout_height="65dp"
    android:layout_alignParentBottom="true"
    app:menu="@menu/bottom_navigation"
    android:background="?android:attr/windowBackground" />

这是 MainActivity

public class MainActivity extends AppCompatActivity {

private Fragment f1;
private Fragment f2;
private Fragment f3;

@Override
protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    f1 = new NotificationsFragment();
    f2 = new SheduleFragment();
    ((SheduleFragment) f2).setGroups(groups);  // it's the second panel with TabLayout
    f3 = new CabinetsFragment();

    BottomNavigationView bottomNav = findViewById(R.id.bottom_navigation);
    bottomNav.setOnNavigationItemSelectedListener(navListener);
    getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, f1).commit();

}


private BottomNavigationView.OnNavigationItemSelectedListener navListener = new BottomNavigationView.OnNavigationItemSelectedListener() {

    @Override
    public boolean onNavigationItemSelected(@NonNull MenuItem menuItem) {

        Fragment selectedFragment = null;

        switch (menuItem.getItemId()) {
            case R.id.navigation_notifications: {
                selectedFragment = f1;
                break;
            }
            case R.id.navigation_shedule:
                selectedFragment = f2;
                break;

            case R.id.navigation_cabinets:
                selectedFragment = f3;
                break;
        }

        getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, selectedFragment).commit();
        return true;
    }
};

}

这是TabLayout的片段，它将位于BottomNavigationView的第二个标签中

<LinearLayout

xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/colorBackground">


<android.support.design.widget.TabLayout
    android:id="@+id/tab_layout"
    android:layout_width="match_parent"
    android:layout_height="25dp"
    app:tabGravity="fill"
    app:tabMode="fixed"
    app:tabTextColor="@color/colorPrimary"
    app:tabIndicatorColor="@color/colorPrimary"
    android:background="@color/colorBackgroundLL">

</android.support.design.widget.TabLayout>

<android.support.v4.view.ViewPager
    android:id="@+id/viewpager"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content">

</android.support.v4.view.ViewPager>
</LinearLayout>

Fragment中的onCreateView函数（TabLayout中的标签为

）

public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState ) {

    View view = inflater.inflate(R.layout.day_layout, container, false);

    rv = (RecyclerView) view.findViewById(R.id.recycler_days_view);

    llm = new LinearLayoutManager(getActivity());
    rv.setLayoutManager(llm);

    ra = new DayRecycleAdapter(teachers,subjects, cabinets,timeBegs, timeEnds  );
    rv.setAdapter(ra);

    return view;
}

底部导航视图中第二个标签的片段

public class SheduleFragment extends Fragment {

private TabLayout tabLayout;
private ViewPager viewPager;

private Group[] groups;
ViewPagerAdapter vpa;

DayFragment df1;
DayFragment df2;
DayFragment df3;
DayFragment df4;
DayFragment df5;
DayFragment df6;


@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState ) {

    View view = inflater.inflate(R.layout.fragment_shedule, container, false);

    df1 = new DayFragment();
    df2 = new DayFragment();
    df3 = new DayFragment();
    df4 = new DayFragment();
    df5 = new DayFragment();
    df6 = new DayFragment();

    tabLayout = (TabLayout)view.findViewById(R.id.tab_layout);
    viewPager = (ViewPager)view.findViewById(R.id.viewpager);

    setNewFragments(df1, df2, df3, df4, df5, df6);

    viewPager.setAdapter(vpa);
    tabLayout.setupWithViewPager(viewPager);

    return view;
}


public void setGroups(Group[] groups) {
    this.groups = groups;
}

public void setNewFragments(DayFragment df1, DayFragment df2, DayFragment df3, DayFragment df4, DayFragment df5, DayFragment df6) {

    vpa = new ViewPagerAdapter(this.getFragmentManager());
    setInfo(df1, df2, df3, df4, df5, df6);

    vpa.addFragment(df1, "пн");
    vpa.addFragment(df2, "вт");
    vpa.addFragment(df3, "ср");
    vpa.addFragment(df4, "чт");
    vpa.addFragment(df5, "пт");
    vpa.addFragment(df6, "сб");
}

public void changeFragments(DayFragment df1, DayFragment df2, DayFragment df3, DayFragment df4, DayFragment df5, DayFragment df6) {

    setOneDayInfo(df1, 0);
    setOneDayInfo(df2, 1);
    setOneDayInfo(df3, 2);
    setOneDayInfo(df4, 3);
    setOneDayInfo(df5, 4);
    setOneDayInfo(df6, 5);
}

public void setInfo(DayFragment df1, DayFragment df2, DayFragment df3, DayFragment df4, DayFragment df5, DayFragment df6) {

    setOneDayInfo(df1, 0);
    setOneDayInfo(df2, 1);
    setOneDayInfo(df3, 2);
    setOneDayInfo(df4, 3);
    setOneDayInfo(df5, 4);
    setOneDayInfo(df6, 5);
}

public void setOneDayInfo(DayFragment df, int i) {

    ArrayList<Lesson> lessons = groups[groupNumber-1].getDays()[i].getLessons();
    int n = lessons.size();

    String[] teachers = new String[n];
    String[] subjects = new String[n];
    String[] cabinets = new String[n];
    String[] timeBegs = new String[n];
    String[] timeEnds = new String[n];

    int j=0;

    for (Lesson les: lessons) {
        teachers[j] = les.teachersToString();
        subjects[j] = les.subjectsToString();
        cabinets[j]= les.cabinetsToString();
        timeBegs[j] = les.timeBegToSting();
        timeEnds[j] = les.timeEndToSting();
        ++j;
    }

    df.setTeachers(teachers);
    df.setSubjects(subjects);
    df.setCabinets(cabinets);
    df.setTimeBegs(timeBegs);
    df.setTimeEnds(timeEnds);

}

}

ViewPagerAdapter：

public class ViewPagerAdapter extends FragmentPagerAdapter {

private final List<Fragment> fragmentList = new ArrayList<>();
private final List<String> fragmentListTitles = new ArrayList<>();

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

@Override
public Fragment getItem(int i) {
    return fragmentList.get(i);
}

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

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

public void addFragment(Fragment fragment, String title) {
    fragmentList.add(fragment);
    fragmentListTitles.add(title);
}

}