animated_visibility.kt

/* Copyright 2019 Google LLC.	
   SPDX-License-Identifier: Apache-2.0 */
fun animateVisibility(view: View, visible: Boolean) {
  val targetAlpha = if (visible) 1f else 0f
  if (view.alpha == targetAlpha) return
  view.visibility = View.VISIBLE
  val spring = view.spring(SpringAnimation.ALPHA)

  (view.getTag(R.id.tag_pending_end_listener) as?
        DynamicAnimation.OnAnimationEndListener)?.let {
    spring.removeEndListener(it)
  }

  if (!visible) {
    val listener = {
      override fun onAnimationEnd() {
        spring.removeEndListener(this)
        view.visibility = View.GONE
      }
    }
    spring.addEndListener(listener)
    view.setTag(R.id.tag_pending_end_listener, listener)
  }
  spring.animateToFinalPosition(targetAlpha)
}