无法更新View Pager中的中间片段。

Question

I've been working on a TAB layout with 3 tabs.

My problem is I'm unable to update,refresh 2nd tab swiping between the pages.

As per my debugging I swipe from tab one to second, the third is being called at getItem(int position), similarly fragment one is being called swiping from third tab to second.

The default getOffscreenPageLimit of viewpager is 1 . I couldn't even set it to zero count.

At getItem, position is 1 at the very beginning but as soon as I swipe page, it only calls position 0 and 2. 1 is never called.

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

This is my ViewPagerSetUp

private void setupViewPager(ViewPager viewPager) {
    ViewPagerAdapter adapter = new 
ViewPagerAdapter(getSupportFragmentManager());
    adapter.addFragment(new InvitedFragment(), "Invited");
    adapter.addFragment(new InterestedFragment(), "Interested");
    adapter.addFragment(new AttendingFragment(), "Attending");
    viewPager.setAdapter(adapter);
}

This is my ViewPager

 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);
    }

    public void refreshFragment(int position) {
        mFragmentList.get(position).onResume();
    }

    @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);
    }
}

addOnPageChangeListener was one option but I couldn't refresh it using pageChangelistener too.

How can I cure offscreenpagelimit ? How can I refresh every tab on every page swipe?

Thank you.

Answer 1

Try this,

Override the below method in fragment.It call when fragment is visible

@Override
public void setUserVisibleHint(boolean isVisibleToUser) {
    super.setUserVisibleHint(isVisibleToUser);
    if (isVisibleToUser) {
        //do your Stuffs
    }
}

Answer 2

add this in your activity

  viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

        }

        @Override
        public void onPageSelected(int position) {
            viewPager.getAdapter().notifyDataSetChanged();
        }

        @Override
        public void onPageScrollStateChanged(int state) {

        }
    });

in your adapter add this,

 @Override
    public int getItemPosition(Object object) {
       return POSITION_NONE;
    }

Answer 3

you have to add View Pager into tabLayout if you not added then try this code:

 tabLayout.setupWithViewPager(viewPager); 

also you are calling Parent Fragment(super) onResume Method in refreshFragment method you have to call SubFragment onResume method :

    mInvitedFragment.onResume();
    mInterestedFragment.onResume();
    mAttendingFragment.onResume();

Answer 4

You can use below method for refresh second fragment.Put this method in the fragment.

@Override
    public void setUserVisibleHint(boolean visible) {
        super.setUserVisibleHint(visible);
        if (visible) {
            //   load data here
        }else {
            // fragment is no longer visible
        }
    }