如何通过父活动上的按钮与ViewPager片段进行交互？

Question

我目前正在开发一个简单的应用来显示闪存卡。目前，我正在使用带有代表卡片的片段的ViewPager，以便在卡片之间滑动。但是，我想在闪存卡下方设置一组静态按钮，以便进行收藏，翻转存储卡以及重新整理卡片组之类的操作。是否可以通过父视图与ViewPager中当前显示的片段进行交互？

活动代码（改编自ViewPager的教程）：

class ViewFlashCardsActivity : FragmentActivity(),
FlashCardFragment.OnFragmentInteractionListener{

private lateinit var mPager: ViewPager

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_view_book)

    // Instantiate a ViewPager and a PagerAdapter.
    mPager = findViewById(R.id.pager)

    // The pager adapter, which provides the pages to the view pager widget.
    val pagerAdapter = FlashCardPagerAdapter(supportFragmentManager)

    mPager.adapter = pagerAdapter
}

override fun onBackPressed() {
    if (mPager.currentItem == 0) {
        // If the user is currently looking at the first step, allow the system to handle the
        // Back button. This calls finish() on this activity and pops the back stack.
        super.onBackPressed()
    } else {
        // Otherwise, select the previous step.
        mPager.currentItem = mPager.currentItem - 1
    }
}

private inner class FlashCardPagerAdapter(fm: FragmentManager) : FragmentStatePagerAdapter(fm) {
    val flashCards = ArrayList<FlashCardFragment>()

    // Static for now for testing
    init {
        flashCards.add(FlashCardFragment.newInstance(0, "Flash card 1", "Back of flash card 1"))
        flashCards.add(FlashCardFragment.newInstance(1, "Flash card 2", "Back of flash card 2"))
        flashCards.add(FlashCardFragment.newInstance(2, "Flash card 3", "Back of flash card 3"))
    }

    override fun getCount(): Int = flashCards.count()

    override fun getItem(position: Int): Fragment = flashCards.get(position)
}

该活动的XML只是具有以下某些按钮的ViewPager。