How to get the instance of the currently visible fragment in ViewPager:

Question

I\'m building an application that shows different fragments in a ViewPager. I add these fragments to the ViewPager like this:

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Answer 1

The way I do it as of year 2020 in Kotlin:

Inside the fragment class I add a public variable:

var fragmentNo = 0

The fragmentNo variable is filled through the adapter's getItem as follows (note fragment.fragmentNo = pos) in particular:

    private inner class ViewPagerAdapter(fragmentManager: FragmentManager)
        : FragmentStatePagerAdapter(fragmentManager, BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT) {

        override fun getCount(): Int = list.size
        var position = 0
        lateinit var fragment: ExerciseFragment

        override fun getItem(pos: Int): Fragment {
            fragment = ExerciseFragment()
            position = pos
            val bundle = Bundle()
            bundle.putSerializable(Constants.WORD_ID, list[position])
            fragment.arguments = bundle
            fragment.fragmentNo = pos
            return fragment
        }

    }

Afterwards, I use the visible fragment in a button clicker, which is outside the viewpager, as follows:

btShowAnswer.setOnClickListener {
            Logger.print(this, "Show Answer Button clicked")

            val fr: ExerciseFragment? = supportFragmentManager.fragments.find {
                it is ExerciseFragment && it.fragmentNo == viewPager.currentItem
            } as? ExerciseFragment

            fr?.showAnswer()

        }

The below line finds the required fragment in particular:

val fr: ExerciseFragment? = supportFragmentManager.fragments.find {
                it is ExerciseFragment && it.fragmentNo == viewPager.currentItem
            } as? ExerciseFragment