Deleting page from FragmentStatePagerAdapter causes issues

Question

Our application has multiple fragments to show data specific to location. We have used FragmentStatePagerAdapter and ViewPager. User should be able to add new page and delete as well. While adding new page works fine, deleting the existing page shows issues. When I verified I had 3 pages. I deleted the 2nd one from left navigation menu button.When I try to slide to the 3rd page, it shows the view of delted page that is 2nd page. ANd it does not show the 3rd page.

I have Overriden getItem() where I return the new page. I have adjusted the ItemCount when I added/deleted the new page to Adapter. And I called startUpdate() before I add/delete, destroy() to delete any fragment object in a position, finishUpdate() after everything done. And finally notifyDataSetChanged().

Looks like nothing is missed but something. I still see the view of deleted fragment and next to it is blank page or something similar depending on which position's page I delete. I see Removing fragments from FragmentStatePagerAdapter is something similar but could not help my case. Help me with any clue.

I recall `FragmentStatePagerAdapter` having problems whenever I tried to change the data behind it (in my case reordering the items). I think I ended up writing my own pager adapter that borrowed from `FragmentStatePagerAdapter` but significantly changed the behavior when handling data set changes. I don't have the code on hand unfortunately... — Karakuri, Jul 10 '15 at 00:29

score 0 · Accepted Answer · edited May 23 '17 at 12:07

I could solve it. Though the answer by Wize here Replace Fragment inside a ViewPager does not solve my issue, I could find a hint from this. I had to override getItemPosition(Object object) which tells system that particulat 'object' is not-changed/no-more-exist.

I have the list of fragments (references) locally as well which I modify according to the list that FragmentStateAdapter maintians and here is my code for getItemPosition():

@Override  
    public int getItemPosition(Object object) {  
       if (object instanceof myFragment) {  
        if (!mFragments.contains(object)) {  
                return POSITION_NONE;  
            } else {
                return mFragments.indexOf(object);  
            }  
        }  
        return super.getItemPosition(object);  
    }

Also, I only called notifyDataSetChanged() after I add/delete fragments. I removed startUpdate(), finishUpdate() all that.I do not knwo where exactly where they are used. But it worked without them.

Deleting page from FragmentStatePagerAdapter causes issues

1 Answers1