Android ViewPager - floating action button clicks

Question

I have the ViewPager and the floating action button in my MainActivity . Each fragment in the ViewPager is a 6x6 GridLayout . On button click, I want to start animation moving ImageView inside the GridLayout . Start and target positions are predefined in the list.

mViewPager = findViewById(R.id.pager)
mViewPager.adapter = mSectionsPagerAdapter
mViewPager.currentItem = currentFragment

val fab: View = findViewById(R.id.floatingActionButton)
fab.setOnClickListener(object : View.OnClickListener {
    override fun onClick(v: View) {
      val c =  mViewPager.currentItem
      val fromView = grid.getChildAt(fromList[c]) as ImageView
      val toView = grid.getChildAt(toList[c]) as ImageView
      val anim = TranslateAnimation(0f, toView.x - fromView.x, 0f, toView.y - fromView.y).apply {
          duration = 500
          fillAfter = false
      }
      fromView.startAnimation(anim)
}

Animation works as expected, but the problem is that it works only on the first page. When I swap to other pages and click the button, nothing happens. When I get back to the first page, also nothing happens. Can someone explain why this is so? How do I fix it? Thank you.

Answer 1

If you are aware of how many "pages" you have in your application, you can set the offscreenpagesize . What happens is sometimes on swiping the pages out of focus, the context of those fragments could be lost.

viewPage.setOffscreenPageLimit(<number of fragments 'tabs'>);

View more details of this method here.

Answer 2

If you have several pages then do not use setOffscreenPageLimit

Try to add fab.setOnClickListener in each fragment.