android - Get current fragment with ViewPager2

Question

I'm migrating my ViewPager to ViewPager2 since the latter is supposed to solve all the problems of the former. Unfortunately, when using it with a FragmentStateAdapter, I don't find any way to get the currently displayed fragment.

viewPager.getCurrentItem() gives the current displayed index and adapter.getItem(index) generally creates a new Fragment for the current index. Unless keeping a reference to all created fragments in getItem(), I have no idea how to access the currently displayed fragment.

With the old ViewPager, one solution was to call adapter.instantiateItem(index) which would return the fragment at the desired index.

Am I missing something with ViewPager2?

Answer 1

In ViewPager2 the FragmentManager by default have assigned tags to fragments like this:

Fragment in 1st position has a tag of "f0"

Fragment in 2nd position has a tag of "f1"

Fragment in 3rd position has a tag of "f2" and so on... so you can get your fragment's tag and by concatenating the "f" with position of your fragment. To get the current Fragment you can get current position from the viewPager2 position and make your tag like this (For Kotlin):

val myFragment = supportFragmentManager.findFragmentByTag("f" + viewpager.currentItem)

For fragment at a certain position

val myFragment = supportFragmentManager.findFragmentByTag("f" + position)

You can cast the Fragment and always check if it is not null if you are using this technique.

If you host your ViewPager2 in Fragment, use childFragmentManager instead.

REMEMBER

If you have overriden the getItemId(position: Int) in your adapter. Then your case is different. It should be:

val myFragment = supportFragmentManager.findFragmentByTag("f" + your_id_at_that_position)

OR SIMPLY:

val myFragment = supportFragmentManager.findFragmentByTag("f" + adapter.getItemId(position))

If you host your ViewPager2 in Fragment, use childFragmentManager instead of supportFragmentManager.