ViewPager2 Adapter to use with Fragments which is dynamically added or removed.

FragmentData.kt

data class FragmentData(val pageId: String)
 

FragmentPagerAdapter.kt

class FragmentPagerAdapter(
    val items: MutableList<FragmentData> = mutableListOf(),
    context: FragmentActivity,
) : FragmentStateAdapter(context) {

    override fun getItemCount(): Int = items.size

    override fun createFragment(position: Int): Fragment {
        return MyFragment
    }

    override fun getItemId(position: Int): Long = itemId(position)
    override fun containsItem(itemId: Long): Boolean = contains(itemId)

    fun submitList(list: List<FragmentData>) {
        items.clear()
        items.addAll(list)
    }

    fun changeDataSet(performChanges: () -> Unit) {
        val idsOld: List<String>
        val idsNew: List<String>

        idsOld = createIdSnapshot()
        performChanges()
        idsNew = createIdSnapshot()

        DiffUtil.calculateDiff(object : DiffUtil.Callback() {

            override fun getOldListSize(): Int = idsOld.size
            override fun getNewListSize(): Int = idsNew.size

            override fun areItemsTheSame(oldItemPosition: Int, newItemPosition: Int) =
                idsOld[oldItemPosition] == idsNew[newItemPosition]

            override fun areContentsTheSame(oldItemPosition: Int, newItemPosition: Int) =
                areItemsTheSame(oldItemPosition, newItemPosition)
        }, false).dispatchUpdatesTo(this)
    }

    private fun createIdSnapshot() = items.map { it.pageId }
    private fun itemId(position: Int): Long = items[position].pageId.toLong()
    private fun contains(itemId: Long): Boolean = items.any { items.any { it.pageId.toLong() == itemId } }
}