带有 viewpager 的片段仅加载一次

Question

I have simple problem.. I have MainActivity.. inside it i have 5 fragments and i can move using bottom navigation bar without problem!

In first fragment (Profile) i have inside that tow fragment using Tablayout and Viewpager.. First Fragment (Friends) Second Fragment (Users)..

My problem when i run app and open (Profile) the tow fragments (Friends and Users) Working 100% just in first time.. when i come back to other fragment using bottom bar and come back to friends or users is empty and not load !

I want attach some of my codes you will need it..

Profile Fragment:

mSectionsPageAdapter = new 
SectionsPageAdapter(getActivity().getSupportFragmentManager());

mViewPager = (ViewPager) v.findViewById(R.id.container);

setupViewPager(mViewPager);

TabLayout tabLayout = (TabLayout) v.findViewById(R.id.tabs);

tabLayout.setupWithViewPager(mViewPager);

mSectionsPageAdapter.notifyDataSetChanged();

private void setupViewPager(ViewPager viewPager) {

SectionsPageAdapter adapter = new 
SectionsPageAdapter(getActivity().getSupportFragmentManager());

adapter.addFragment(new FriendsFragment(), "Friends");
adapter.addFragment(new UsersFragment(), "Online");

viewPager.setAdapter(adapter);
}

SectionsPageAdapter:

public class SectionsPageAdapter extends FragmentPagerAdapter {

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

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

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

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

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

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

I try to add this in Friends Fragment and Users Fragment the problem was solved but the content duplicated in first time run only.

   @Override
public void setUserVisibleHint(boolean isVisibleToUser) {
    super.setUserVisibleHint(isVisibleToUser);
    if (isVisibleToUser) {
        getFragmentManager().beginTransaction().detach(this).attach(this).commit();

    }
}

SectionsPageAdapter:

public class SectionsPageAdapter extends FragmentPagerAdapter {

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

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

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

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

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

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

Answer 1

You can use interface to solve this problem. Implement interface in your "User" & "Friend" fragments & call the interface method when your "Profile" fragments "OnCreateView" is called. You can load data when interface method is called. For reference, Please check this link: Communicating with Other Fragments

EDIT

Sorry,you can load data without using Interface. Here is some sample code:

Profile Fragment:

ProfileFragment extends Activity  {
    FriendsFragment friends;
    UsersFragment users;
           @Override
           public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
                      mSectionsPageAdapter = new 
                      SectionsPageAdapter(getActivity().getSupportFragmentManager());

                      mViewPager = (ViewPager) v.findViewById(R.id.container);

                      setupViewPager(mViewPager);

                      TabLayout tabLayout = (TabLayout) v.findViewById(R.id.tabs);

                      tabLayout.setupWithViewPager(mViewPager);

                       mSectionsPageAdapter.notifyDataSetChanged();

                      friends.update();
                      users.update();
}

       private void setupViewPager(ViewPager viewPager) {

                       SectionsPageAdapter adapter = new 
                    SectionsPageAdapter(getActivity().getSupportFragmentManager());
                       friends = new FriendsFragment();
                       users = new UsersFragment();
                       adapter.addFragment(friends, "Friends");
                       adapter.addFragment(users, "Online");
                       viewPager.setAdapter(adapter);
    }

Friends Fragment:

FriendFragment extends Activity  {
    public void update(){
        // load data 
    }

Answer 2

A possible reason for your problems could be you are mixing up FragmentManager s.

In your Activity to handle the bottom navigation you should use Activity#getSupportFragmentManager() .

But for any of the Fragment s inside that activity, if you want to have children/nested fragments. You should use Fragment#getChildFragmentManager() .

So in your profile fragment, while populating the two tabs pager, you should pass it Fragment#getChildFragmentManager() instead of getActivity().getSupportFragmentManager()

Answer 3

jest Use

ViewPagerAdapter(getChildFragmentManager())

• getChildFragmentManager()