RecyclerView的项目在Tablayout中显示第一次但在第二次显示时不显示

Question

关于TabLayout与ViewPager我有一些问题。我在RecyclerView的片段中实现了Tablayout。这个TabLayout是在一个Fragment的Nevigation Drawer项目上实现的。

当我点击带有TabLayout的Nevigation Drawer'Fragments视图时，RecyclerView的项目也会在第一时间显示。但点击第二次NevigationDrawer，RecyclerView的项目没有显示。为什么...？

public class DashBoardRequest extends Fragment implements TabLayout.OnTabSelectedListener{

    private TabLayout tabLayout;
    private ViewPager viewPager;
    View view;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        view= inflater.inflate(R.layout.fragment_dash_board_request, container, false);
        tabLayout = (TabLayout)view.findViewById(R.id.tab);
        viewPager = (ViewPager)view.findViewById(R.id.viewPager);
        setupViewPager(viewPager);
        viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
        tabLayout.setupWithViewPager(viewPager);
        tabLayout.setSelectedTabIndicatorColor(getResources().getColor(R.color.colorPrimary));
        tabLayout.setTabTextColors(ContextCompat.getColorStateList(getContext(), R.color.colorPrimaryDark));
        return view;
    }

    @Override
    public void onTabSelected(TabLayout.Tab tab) {
        viewPager.setCurrentItem(tab.getPosition());
    }

    @Override
    public void onTabUnselected(TabLayout.Tab tab) { }

    @Override
    public void onTabReselected(TabLayout.Tab tab) { }

    private void setupViewPager(ViewPager viewPager){
        ViewPagerAdapter adapter = new ViewPagerAdapter(getFragmentManager());
        adapter.addFragment(new AcceptedClientClass(), "Accepted");
        adapter.addFragment(new RejectedClientClass(), "Rejected");
        viewPager.setAdapter(adapter);
    }

    class ViewPagerAdapter extends FragmentPagerAdapter {

        private final List<Fragment> mFragmentList = new ArrayList<>();
        private final List<String> mFragmentTitleList = new ArrayList<>();

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

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

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

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

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

Answer 1

您可以使用FragmentStatePagerAdapter或使用viewpager。 setOffscreenPageLimit（）根据您的要求。

Answer 2

我用这个解决了我的问题： -

解决： - 从FragmentPagerAdapter替换FragmentStatePagerAdapter

public class DashBoardRequest extends Fragment实现TabLayout.OnTabSelectedListener {

private TabLayout tabLayout;
private ViewPager viewPager;
View view;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    view= inflater.inflate(R.layout.fragment_dash_board_request, container, false);
    tabLayout = (TabLayout)view.findViewById(R.id.tab);
    viewPager = (ViewPager)view.findViewById(R.id.viewPager);
    setupViewPager(viewPager);
    viewPager.setOffscreenPageLimit(1);
    viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
    tabLayout.setupWithViewPager(viewPager);
    tabLayout.setSelectedTabIndicatorColor(getResources().getColor(R.color.colorPrimary));
    tabLayout.setTabTextColors(ContextCompat.getColorStateList(getContext(), R.color.colorPrimaryDark));
    return view;
}

@Override
public void onTabSelected(TabLayout.Tab tab) {
    viewPager.setCurrentItem(tab.getPosition());
}

@Override
public void onTabUnselected(TabLayout.Tab tab) { }

@Override
public void onTabReselected(TabLayout.Tab tab) { }

private void setupViewPager(ViewPager viewPager){
    ViewPagerAdapter adapter = new ViewPagerAdapter(getFragmentManager());
    adapter.addFragment(new AcceptedClientClass(), "Accepted");
    adapter.addFragment(new RejectedClientClass(), "Rejected");
    viewPager.setAdapter(adapter);
}

class ViewPagerAdapter extends FragmentStatePagerAdapter {

    private final List<Fragment> mFragmentList = new ArrayList<>();
    private final List<String> mFragmentTitleList = new ArrayList<>();

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

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

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

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

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