AnimatorSet.setDuration问题

最近在使用RippleBackground这个开源代码，做水波纹的动画效果，里面有一部分代码是这样的：

animatorSet = new AnimatorSet();
animatorSet.setInterpolator(new AccelerateDecelerateInterpolator());
animatorSet.setDuration(rippleDurationTime);
animatorList = new ArrayList<Animator>();

for (int i = 0; i < rippleAmount; i++) {
RippleView rippleView = new RippleView(getContext());
addView(rippleView, rippleParams);
rippleViewList.add(rippleView);
final ObjectAnimator scaleXAnimator = ObjectAnimator.ofFloat(rippleView, "ScaleX", 1.0f, rippleScale);
scaleXAnimator.setRepeatCount(ObjectAnimator.INFINITE);
scaleXAnimator.setRepeatMode(ObjectAnimator.RESTART);
scaleXAnimator.setStartDelay(i * rippleDelay);
animatorList.add(scaleXAnimator);
final ObjectAnimator scaleYAnimator = ObjectAnimator.ofFloat(rippleView, "ScaleY", 1.0f, rippleScale);
scaleYAnimator.setRepeatCount(ObjectAnimator.INFINITE);
scaleYAnimator.setRepeatMode(ObjectAnimator.RESTART);
scaleYAnimator.setStartDelay(i * rippleDelay);
animatorList.add(scaleYAnimator);
final ObjectAnimator alphaAnimator = ObjectAnimator.ofFloat(rippleView, "Alpha", 1.0f, 0f);
alphaAnimator.setRepeatCount(ObjectAnimator.INFINITE);
alphaAnimator.setRepeatMode(ObjectAnimator.RESTART);
alphaAnimator.setStartDelay(i * rippleDelay);
animatorList.add(alphaAnimator);
}

animatorSet.playTogether(animatorList);这是那个波纹的动画效果，我之前测试机一直是4.1系统的，一切正常。今天无意间用一个4.0.3的手机跑了一下，发现setDuration失效了。然后我又拿了一台4.0.2系统的手机测，发现依旧失效，然后将代码改为：
animatorSet = new AnimatorSet();
animatorSet.setInterpolator(new AccelerateDecelerateInterpolator());
animatorList = new ArrayList<Animator>();

for (int i = 0; i < rippleAmount; i++) {
RippleView rippleView = new RippleView(getContext());
addView(rippleView, rippleParams);
rippleViewList.add(rippleView);
final ObjectAnimator scaleXAnimator = ObjectAnimator.ofFloat(rippleView, "ScaleX", 1.0f, rippleScale);
scaleXAnimator.setRepeatCount(ObjectAnimator.INFINITE);
scaleXAnimator.setRepeatMode(ObjectAnimator.RESTART);
scaleXAnimator.setStartDelay(i * rippleDelay);
scaleXAnimator.setDuration(rippleDurationTime);
animatorList.add(scaleXAnimator);
final ObjectAnimator scaleYAnimator = ObjectAnimator.ofFloat(rippleView, "ScaleY", 1.0f, rippleScale);
scaleYAnimator.setRepeatCount(ObjectAnimator.INFINITE);
scaleYAnimator.setRepeatMode(ObjectAnimator.RESTART);
scaleYAnimator.setStartDelay(i * rippleDelay);
scaleYAnimator.setDuration(rippleDurationTime);
animatorList.add(scaleYAnimator);
final ObjectAnimator alphaAnimator = ObjectAnimator.ofFloat(rippleView, "Alpha", 1.0f, 0f);
alphaAnimator.setRepeatCount(ObjectAnimator.INFINITE);
alphaAnimator.setRepeatMode(ObjectAnimator.RESTART);
alphaAnimator.setStartDelay(i * rippleDelay);
alphaAnimator.setDuration(rippleDurationTime);
animatorList.add(alphaAnimator);
}

animatorSet.playTogether(animatorList);

就正常了。其实就是把Duration在每个动画里set一下，其实具体我还没搞清楚为什么在4.0.x上用animatorSet去设置Duration无效的原因，希望能和大家讨论一下。