Android 使用cos和sin绘制复合曲线动画

private fun animateTagView(tagView: TextView) {
 // [0,200]区间的动画 
 val valueAnimatorOne = ValueAnimator.ofInt(0, 200)
 valueAnimatorOne.addUpdateListener {
  val per = it.animatedValue as Int / 200f
  tagView.rotation = 4 * per
  tagView.scaleX = (1 - 0.1 * per).toFloat()
  tagView.scaleY = (1 - 0.1 * per).toFloat()
 }
 valueAnimatorOne.duration = 200
 // [200,560]区间的动画
 val valueAnimatorTwo = ValueAnimator.ofInt(200, 560)
 valueAnimatorTwo.addUpdateListener {
  val per = (it.animatedValue as Int - 200) / 360f
  tagView.rotation = 3 - 11 * per
  tagView.scaleX = (0.9 + 0.1 * per).toFloat()
  tagView.scaleY = (0.9 + 0.1 * per).toFloat()
 }
 valueAnimatorTwo.duration = 360
 // [560,840]区间的动画
 val valueAnimatorThree = ValueAnimator.ofInt(560, 840)
 valueAnimatorThree.addUpdateListener {
  val per = (it.animatedValue as Int - 560) / 280f
  tagView.rotation = -8 + 12 * per
  tagView.scaleX = (1 - 0.2 * per).toFloat()
  tagView.scaleY = (1 - 0.2 * per).toFloat()
 }
 valueAnimatorThree.duration = 280
 // [840,1000]的动画
 val valueAnimatorFour = ValueAnimator.ofInt(840, 1000)
 valueAnimatorFour.addUpdateListener {
  val per = (it.animatedValue as Int - 840) / 160f
  tagView.rotation = 4 - 4 * per
  tagView.scaleX = (0.8 + 0.2 * per).toFloat()
  tagView.scaleY = (0.8 + 0.2 * per).toFloat()
 }
 valueAnimatorFour.duration = 160
 // 使用AnimatorSet串行执行动画
 val animationSet = AnimatorSet()
 animationSet.playSequentially(valueAnimatorOne, valueAnimatorTwo, valueAnimatorThree, valueAnimatorFour)
 tagView.post {
  tagView.pivotX = 0f
  tagView.pivotY = ad_tag_two.measuredHeight.toFloat()
  animationSet.start()
 }
}

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

 val tvContent = findViewById<TextView>(R.id.tv_content)
 val valueAnimatorOne = ValueAnimator.ofFloat(0.0f, 1.5f)
 valueAnimatorOne.addUpdateListener {
  // 通过对应的sin和cos设置rotation和scale
  val per = it.animatedValue as Float
  var rotation: Float = 0f
  var scale: Float = 0f
  if(per >= 0 && per < 0.2f){
   rotation = sin((per / 0.2f) * Math.PI.toFloat() - Math.PI.toFloat() / 2) * 1.5f + 1.5f
   scale = cos(per / 0.2f * Math.PI.toFloat()) * 0.05f + 0.95f
  }
  if(per >= 0.2f && per < 0.56f){
   rotation = sin(Math.PI.toFloat() / 2 + Math.PI.toFloat() * ( per - 0.2f) / 0.36f) * 5.5f - 2.5f
   scale = cos((per - 0.2f) / 0.36f * Math.PI.toFloat() + Math.PI.toFloat()) * 0.05f + 0.95f
  }
  if(per >= 0.56f && per < 0.84f){
   rotation = sin(Math.PI.toFloat() * (per - 0.56f) / 0.28f - Math.PI.toFloat() / 2) * 6f - 2f
   scale = cos((per - 0.56f) / 0.28f * Math.PI.toFloat()) * 0.1f + 0.9f
  }
  if(per in 0.84f..1f){
   rotation = sin(Math.PI.toFloat() / 2 + Math.PI.toFloat() * (per - 0.84f) / 0.16f ) * 2f + 2f
   scale = cos((per - 0.84f) / 0.16f * Math.PI.toFloat() + Math.PI.toFloat()) * 0.1f + 0.9f
  }
  // 设置停止时间
  if(per > 1f && per <= 1.5f){
   rotation = 0f
   scale = 1.0f
  }
  tvContent.rotation = rotation
  tvContent.scaleX = scale
  tvContent.scaleY = scale
 }
 // 设置线性插值器
 valueAnimatorOne.interpolator = LinearInterpolator()
 // 动画时间
 valueAnimatorOne.duration = 1500
 // 无线循环
 valueAnimatorOne.repeatCount = -1
 tvContent.post {
  // 设置中心点
  tvContent.pivotX = 0f
  tvContent.pivotY = tvContent.measuredHeight.toFloat()
  valueAnimatorOne.start()
 }
}