android 4.0.x上AnimatorSet.setDuration上的坑

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<span style="font-size:18px;">  最近在用<a target=_blank href="https://github.com/skyfishjy/android-ripple-background">https://github.com/skyfishjy/android-ripple-background</a>开源控件的时候，在Android4.0.x上遇到一个问题，本来优雅的动画变得很快。</span>

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<span style="font-size:18px;">  刚开始以为是硬件加速的问题，但是查资料后，发现google在4.0的时候就默认的把硬件加速打开了，所以之上的版本都应该一样的。后来和同事一起研究的时候发现，好像是animatorSet.setDuration()方法没有效果，又查了源码发现下面的区别：</span>

API 15

/**
     * Sets the length of each of the current child animations of this AnimatorSet. By default,
     * each child animation will use its own duration. If the duration is set on the AnimatorSet,
     * then each child animation inherits this duration.
     *
     * @param duration The length of the animation, in milliseconds, of each of the child
     * animations of this AnimatorSet.
     */
    @Override
    public AnimatorSet setDuration(long duration) {
        if (duration < 0) {
            throw new IllegalArgumentException("duration must be a value of zero or greater");
        }
        // Just record the value for now - it will be used later when the AnimatorSet starts
        mDuration = duration;
        return this;
    }

API 19

    /**
     * Sets the length of each of the current child animations of this AnimatorSet. By default,
     * each child animation will use its own duration. If the duration is set on the AnimatorSet,
     * then each child animation inherits this duration.
     *
     * @param duration The length of the animation, in milliseconds, of each of the child
     * animations of this AnimatorSet.
     */
    @Override
    public AnimatorSet setDuration(long duration) {
        if (duration < 0) {
            throw new IllegalArgumentException("duration must be a value of zero or greater");
        }
        for (Node node : mNodes) {
            // TODO: don't set the duration of the timing-only nodes created by AnimatorSet to
            // insert "play-after" delays
            node.animation.setDuration(duration);
        }
        mDuration = duration;
        return this;
    }

原来是在API15上AnimatorSet.setDuration()方法并没有给它的子objectAnimator设置，解决方案当然是给每个add到animatorSet中的ObjectAnimator都设置自己的duration。

这是最典型的Android版本兼容问题，踩过坑了就不要再犯。