RadialTimePickerView.java 文件源码

private static ObjectAnimator getFadeInAnimator(IntHolder target, int startAlpha, int endAlpha,
                                                InvalidateUpdateListener updateListener) {
    final float delayMultiplier = 0.25f;
    final float transitionDurationMultiplier = 1f;
    final float totalDurationMultiplier = transitionDurationMultiplier + delayMultiplier;
    final int totalDuration = (int) (FADE_IN_DURATION * totalDurationMultiplier);
    final float delayPoint = (delayMultiplier * FADE_IN_DURATION) / totalDuration;

    final Keyframe kf0, kf1, kf2;
    kf0 = Keyframe.ofInt(0f, startAlpha);
    kf1 = Keyframe.ofInt(delayPoint, startAlpha);
    kf2 = Keyframe.ofInt(1f, endAlpha);
    final PropertyValuesHolder fadeIn = PropertyValuesHolder.ofKeyframe("value", kf0, kf1, kf2);

    final ObjectAnimator animator = ObjectAnimator.ofPropertyValuesHolder(target, fadeIn);
    animator.setDuration(totalDuration);
    animator.addUpdateListener(updateListener);
    return animator;
}