动画的Interpolator 弹性

public class JellyInterpolator extends LinearInterpolator {
   private float factor;

   public JellyInterpolator() {
      this.factor = 0.15f;
   }

   @Override
   public float getInterpolation(float input) {
      return (float) (Math.pow(2, -10 * input)
            * Math.sin((input - factor / 4) * (2 * Math.PI) / factor) + 1);
   }
}