How to replace fragment at a position in viewpager tab?

Question

I have 3 tabs in viewpager. Lets call them tab A,B,C. Each of the tabs have their own fragments, lets call them frag1, frag2, frag3. I want to replace frag1 in tab A with a new fragment frag4 and leave the other tabs in viewpager untouched. I have tried replacing the fragment but it doesnt work. Do i need to implement something in my pageradapter ?

public class SectionsPagerAdapter extends FragmentPagerAdapter {

private FragmentManager mFragmentManager;
private Fragment frag = null;

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


public void onSwitchToNextFragment() {
    mFragmentManager.beginTransaction().remove(frag)
            .commit();
    if (frag instanceof Fragment1){

        Log.v("here","swapping");
        frag = Fragment4.newInstance();
    }
    Log.v("here","notified");
    notifyDataSetChanged();
}
@Override
public Fragment getItem(int position) {
    switch (position) {
        case 0:
            frag = Fragment1.newInstance();
            Log.v("here","in getitem");
            return frag;

        default:
            Log.v("here","in default");
            return Fragment2.newInstance();
    }
}

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

@Override
public CharSequence getPageTitle(int position) {
    switch (position) {
        case 0:
            return "SECTION 1";
        case 1:
            return "SECTION 2";
        case 2:
            return "SECTION 3";
    }
    return null;
}

public void switchFrag(){
      onSwitchToNextFragment();
    //    mFragmentManager.beginTransaction().replace(R.id.container,frag).commit();
    //        mFragmentManager.beginTransaction().add(frag).commit();
    notifyDataSetChanged();
}

Christoph Mayr Christoph Mayr · Accepted Answer · 2017-04-16T03:11:48

There are two ways to replace a fragment in a viewpager. Option one: Override the getItemPosition(Object object) method.

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

When you call notifyDataSetChanged(), the view pager will remove all views and reload them all. But this is not very efficient.

Or you call instantiateItem() when instantiating a new view. Then instead of using notifyDataSetChanged(), you can use findViewWithTag() to find the view you want to update. This option is more efficient and flexible

How to replace fragment at a position in viewpager tab?

1 Answers