FragmentPagerAdapterThatRestoresFragmentInstances.kt

/**
 * This class is FragmentPagerAdapter where all the fragments are in an array and you can access to them later.
 * @property mFragments the list of fragments,
 * @property NUMBER_OF_FRAGMENTS the total number of fragments that will be created. Change the value of this param accordingly.
 */
class MyFragmentPagerAdapter(fm: FragmentManager) : FragmentPagerAdapter(fm) {
    companion object {
        private val NUMBER_OF_FRAGMENTS = 2
    }

    private val mFragments = SparseArray<Fragment>()

    override fun getCount(): Int {
        return NUMBER_OF_FRAGMENTS
    }

    override fun getItem(position: Int): Fragment {
        TODO("Here you create and return the fragment instances")
    }

    override fun instantiateItem(container: ViewGroup, position: Int): Any {
        val fragment = super.instantiateItem(container, position) as Fragment
        mFragments.put(position, fragment)
        return fragment
    }

    override fun destroyItem(container: ViewGroup, position: Int, `object`: Any) {
        mFragments.remove(position)
        super.destroyItem(container, position, `object`)
    }

    /**
     * Returns the instance of the fragment if it is created, null otherwise.
     */
    fun getFragment(position: Int): Fragment? {
        return if (mFragments.size() == 0) {
            null
        } else mFragments.get(position)
    }
}