Fragment中的ViewPager，只有选项卡才能在第一个视图上加载选项卡

Posted 2021-04-17

我有一个带有选项卡的片段，它使用了一个视图寻呼机。问题是当我第一次访问片段时会出现选项卡，但如果我导航到其他地方然后返回到此片段，则视图寻呼机中的片段不再出现。

我使用SectionsPagerAdapter如下：

public class SectionsPagerAdapter extends FragmentPagerAdapter {

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

@Override
public Fragment getItem(int position) {
    // getItem is called to instantiate the fragment for the given page.
    // Return a PlaceholderFragment (defined as a static inner class below).
    switch (position) {
        case 0:
            //ClientHealthRootFragment tab1 = new ClientHealthRootFragment();
            ChatListFragment tab1 = new ChatListFragment();
            return tab1;
        case 1:
            ClientProfileFragment tab2 = new ClientProfileFragment();
            //ChatListFragment tab2 = new ChatListFragment();
            return tab2;
        case 2:
            //ClientCommentRootFragment tab3 = new ClientCommentRootFragment();
            ChatListFragment tab3 = new ChatListFragment();
            return tab3;
        default:
            return null;
    }
}

@Override
public int getCount() {
    // Show 3 total pages.
    return 3;
}

@Override
public CharSequence getPageTitle(int position) {
    switch (position) {
        case 0:
            return "Health";
        case 1:
            return "Profile";
        case 2:
            return "Comments";
    }
    return null;
}}

然后在我处理部分的片段中如下：

public class ClientMainFragment extends Fragment {

private ViewPager mViewPager;

SectionsPagerAdapter mSectionsPagerAdapter;

String client_name;
int client_image;

private TextView clientNameText;
private ImageView clientImage;

public ClientMainFragment() {
    //empty constructor
}

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.fragment_client_main, container, false);

    clientNameText =  view.findViewById(R.id.clientNameTxt);
    clientImage =  view.findViewById(R.id.clientImage);

    // Create the adapter that will return a fragment for each of the three
    // primary sections of the activity.
    mSectionsPagerAdapter = new SectionsPagerAdapter(getFragmentManager());

    // Set up the ViewPager with the sections adapter.
    mViewPager = (ViewPager) view.findViewById(R.id.viewPager);
    mViewPager.setAdapter(mSectionsPagerAdapter);

    TabLayout tabLayout = (TabLayout) view.findViewById(R.id.tab_layout);
    tabLayout.setupWithViewPager(mViewPager);

    return view;
}}

我不确定我错过了什么，任何帮助将不胜感激。

编辑：解决方案

我通过以下链接找出问题所在：Tab content disappeared after change page

答案

处理片段生命周期实现覆盖方法如下：

@Override
public void onResume() {
    super.onResume();
}

并在onReume方法中将以下viewpager代码的Hole Code放入：

mSectionsPagerAdapter = new SectionsPagerAdapter(getFragmentManager());

// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) view.findViewById(R.id.viewPager);
mViewPager.setAdapter(mSectionsPagerAdapter);

TabLayout tabLayout = (TabLayout) view.findViewById(R.id.tab_layout);
tabLayout.setupWithViewPager(mViewPager);

所以最终守则将是：

@Override
public void onResume() {
    super.onResume();
    mSectionsPagerAdapter = new SectionsPagerAdapter(getFragmentManager());

// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) view.findViewById(R.id.viewPager);
mViewPager.setAdapter(mSectionsPagerAdapter);

TabLayout tabLayout = (TabLayout) view.findViewById(R.id.tab_layout);
tabLayout.setupWithViewPager(mViewPager);
}