第三章 属性动画

1. ValueAnimator实战

   // 属性值从0变化到400
   val valueAnimator = ValueAnimator.ofInt(0, 400)
   valueAnimator.duration = 1000
   valueAnimator.start()
   // 添加监听器
   valueAnimator.addUpdateListener { animation ->
       val animatedValue = animation.animatedValue as Int
       img.layout(animatedValue, animatedValue, animatedValue + img.width, animatedValue + img.height)
   }

2. 自定义插值器与Evaluator

   1. 自定义插值器

      valueAnimator.interpolator = Interpolator { input ->
          // input代表动画时间内的进度，从0-1匀速变化，此时变化是平方级变化
          // 取值可以小于0或者大于1，可以参考AnticipateOvershootInterpolator
          input * input }

   2. Evaluator

      

      valueAnimator.setEvaluator { fraction, startValue, endValue -> 
           // fraction 代表
           fraction * (startValue as Int - endValue as Int) + endValue 
      }

   3. ValueAnimator进阶——ofObject

      // 自定义Evaluator
      val evaluator : TypeEvaluator<Char> = TypeEvaluator { fraction, startValue, endValue ->
          val fl = startValue.toInt() + fraction * (endValue.toInt() - startValue.toInt())
          fl.toChar()
      }
      ?
      // 需要传入自定义Evaluator，告知动画执行过程中的值
      val ofObjectAnim = ValueAnimator.ofObject(evaluator, ‘A‘, ‘z‘)
      ofObjectAnim.start()
      ofObjectAnim.addUpdateListener { animation ->
          charTv.setText(animation.getAnimatedValue().toString())
      }

3. ObjectAnimator

   val arrayOf = arrayOf("alpha", "rotation", "rotationX", "rotationY", "scaleX", "scaleY")
   // 通过反射
   objAnim = ObjectAnimator.ofFloat(image, arrayOf[animCount], 0f, 300f)

4. 组合动画——AnimatorSet

   1. playSequentially() 依次播放

      val animatorSet = AnimatorSet()
      animatorSet.playSequentially(objAnim, objAnim)

   2. playTogether() 同时播放

      val animatorSet = AnimatorSet()
      animatorSet.playTogether(objAnim, objAnim)

   3. AnimatorSet.Builder

      1. 同时播放动画

         val animatorSet = AnimatorSet()
         val builder = animatorSet.play(objAnim)
         builder.with(objAnim)

      2. 其他函数

         before
         after
         都是以play()中当前所播放的动画为基准的

5. Animator动画的XML实现

   1. ValueAnimator的XML实现

      1. 定义XML文件

         <animator xmlns:android="http://schemas.android.com/apk/res/android"
             android:duration="1000"
             android:valueFrom="0"
             android:valueTo="300"
             android:startOffset="1000"
             android:repeatCount="infinite"
             android:repeatMode="reverse"
             android:valueType="intType"
             android:interpolator="@android:anim/anticipate_overshoot_interpolator"/>

      2. 代码中执行

         val loadAnimator = AnimatorInflater.loadAnimator(this, R.animator.animator) as ValueAnimator
         loadAnimator.addUpdateListener { animation ->
           val offset = animation.getAnimatedValue() as Int
           image.layout(offset, offset, image.width + offset, image.height + offset)
         }
         loadAnimator.start()

   2. ObjectAnimator的XML实现

      1. 定义XML文件

         <?xml version="1.0" encoding="utf-8"?>
         <objectAnimator xmlns:android="http://schemas.android.com/apk/res/android"
             android:propertyName="TranslationY"
             android:duration="1000"
             android:valueFrom="0f"
             android:valueTo="400f"
             android:valueType="floatType"
             android:startOffset="500"
             android:repeatMode="reverse"
             android:repeatCount="infinite"
             android:interpolator="@android:anim/anticipate_overshoot_interpolator"/>

          

      2. 代码中执行

         val objectAnimator =
                     AnimatorInflater.loadAnimator(this, R.animator.obj_animator) as ObjectAnimator
         ?
         objectAnimator.target = image
         objectAnimator.start()

原文：https://www.cnblogs.com/youngly15/p/13157156.html