Android changing fragment order inside FragmentPagerAdapter
android, android-fragments, android-viewpager, fragmentpageradapter, java
Solution
You also need to override `getItemPosition()`. By default, this function always returns `POSITION_UNCHANGED`, so that when you call `notifyDataSetChanged()`, the adapter assumes that all of the fragments are still in the same position. (It does not call `getItem()` again, since it thinks all of the necessary fragments are already created.) Your new `getItemPosition()` should return the new position of each fragment after shuffling.
An easy hack is to always return `POSITION_NONE`, and then the adapter will just discard all of the existing fragments, and recreate them in their correct positions when calling `getItem()`. Of course, this is not efficient, and has the additional drawback that the current fragment being viewed may change. However, since there may possibly be some bugs in reordering the fragments - see my question here - the `POSITION_NONE` approach may be the safest method.
Problem
I have ~20 fragments inside FragmentPagerAdapter that contains a list where it picks the fragments from so theres no recreation of fragments. ``` private List<TitledFragment> fragments; public SectionsPagerAdapter(FragmentManager fm) { super(fm); this.fragments = new ArrayList<TitledFragment>(); } @Override public Fragment getItem(int i) { return fragments.get(i).getFragment(); } @Override public int getCount() { return fragments.size(); } @Override public CharSequence getPageTitle(int position) { return fragments.get(position).getTitle(); } public synchronized List<TitledFragment> getFragments() { return fragments; } public synchronized void addFragment(TitledFragment fragment) { fragments.add(fragment); notifyDataSetChanged(); } ``` the FragmentPagerAdapter is set as adapter of ViewPager and after that I reorder the fragments(shuffling was just for test) ``` Collections.shuffle(mSectionsPagerAdapter.getFragments()); mSectionsPagerAdapter.notifyDataSetChanged(); ``` and for some reason only order of titles is being changed, even if its returning different fragment for getItem as the order is different. Why is this and how can I get around it?