How to add nextset of fragments without disturbing current fragments in FragmentPagerAdapter?

Question

Here's the code to add the fragments for first time`

`if(mcursor==null) { items = (ArrayList) cnews.getItems(); mcursor = cnews.getNextPageToken();

        for (int i = 0; i < items.size(); i++) {

            Fragment cm = ContentFragment.newInstance(i, items.get(i).getTitle(),
                    items.get(i).getImageuri(), items.get(i).getDate(), items.get(i).getPublsher(), items.get(i).getDescription());
            frags.add(cm);

        }
        viewPager.setAdapter(new ContentfragmentAdapter(getSupportFragmentManager(), frags));

    }else{
        items = (ArrayList<News>) cnews.getItems();
        mcursor = cnews.getNextPageToken();
        for (int i = 0; i < items.size(); i++) {

            Fragment cm = ContentFragment.newInstance(i, items.get(i).getTitle(),
                    items.get(i).getImageuri(), items.get(i).getDate(), items.get(i).getPublsher(), items.get(i).getDescription());
            frags.add(cm);

        }

In else condition i want to add some more fragments after server call.How can i update the adapter without removing old fragments?

Please help me i am newbie in android development. Thanks in Adavance.

Answer 1

One of the crucial parts here is that you must call

notifyDataSetChanged()

on the adapter so that the underlying data structures are updated accordingly including triggering a redraw of the ViewPager. Also don't forget that getCount() must also return the expected number of elements (ie. no hardcoding values here)

public class SectionsPagerAdapter extends FragmentPagerAdapter {

    List<String> tagList;

    public SectionsPagerAdapter(FragmentManager fm) {
        super(fm);
        tagList = new ArrayList<>();

    }

    @Override
    public Fragment getItem(int position) {
        // getItem is called to instantiate the fragment for the given page.

        return PlaceholderFragment.newInstance(tagList.get(position));
    }

    @Override
    public int getCount() {

        return tagList.size();
    }

    @Override
    public CharSequence getPageTitle(int position) {

        return "SECTION "+(position+1);
    }

    public void add(int position, String key)
    {
        tagList.add(position, key);
        notifyDataSetChanged();
    }



}