Be careful with findFragmentById() to find fragments inside a FragmentStatePagerAdapter

Hi,

I found your blog post while searching for my own bug with FragmentStatePagerAdapter.

So I'll share my experience...

You can test this bug on support library 23.1.1:

• Put a ViewPager on your activity and use a FragmentStatePagerAdapter as adapter, which provides a list of fragments.
• Each fragment saves its own index within the adapter in its arguments (you provide that index).
• On each fragment, put a button. When a button is clicked, you get the fragment manager, and call findFragmentById() with the current fragment ID (via getId()).
• Take the result fragment, get the index back to compare it to current fragment index.

The bug is: findFragmentById() returns random fragment. The index number is wrong in most case.

So be careful :-)

[adamsp]

Thanks for the tip. I haven't touched this in years, but I'll leave this open so hopefully anyone else who comes across this can benefit from your experiences.