Question

我目前有一个动画用作视频的进度指示器，效果很好。但是，现在我们有一个功能，允许用户通过点击它跳过2.5秒前进到视频，因此我试图实现进度指示器动画向前跳过动画2.5秒。我如何向前跳过动画2.5秒？我试过＆＃34; animationGroup.timeOffset = 2.5＆＃34;但它没有用。

for x in array:
    if(condition):
        do stuff
    else:
        do other stuff

//这是我绘制externalCircle的地方：

func performProgressIndicatorAnimation(duration: Float64) {
    layer.mask = nil
    layer.speed = 1.0

    self.duration = duration
    let strokeStartAnimation = CABasicAnimation(keyPath: "strokeStart")
    strokeStartAnimation.fromValue = 0
    strokeStartAnimation.toValue = 1
    strokeStartAnimation.duration = duration
    strokeStartAnimation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionLinear)

    animationGroup = CAAnimationGroup()
    animationGroup.duration = duration
    animationGroup.animations = [strokeStartAnimation]
    externalCircle.addAnimation(animationGroup, forKey: "animationGroup")

}

Answer 1

如果使用timeOffset跳过一定比例的动画，它仍会播放相同的总持续时间。动画只是循环播放并再次播放，直到它最初开始的位置。例如：动画：A-> B-> C。如果你使用timeOffSet从B开始，它将是：B-＆gt; C-＆gt; A

在这种情况下，我认为您可以忽略此动画，然后添加新动画。

Answer 2

通过删除上一个动画并根据经过的百分比（跳过）启动它

func skipProgressIndicatorAnimation(currentTime: CMTime, timeToSkip: Double, duration: CMTime) {

    animationGroup = nil
    externalCircle.removeAllAnimations()

    let percentageElapsedWithSkip = (CMTimeGetSeconds(currentTime) + timeToSkip) / CMTimeGetSeconds(duration)

    let strokeStartAnimation = CABasicAnimation(keyPath: "strokeStart")
    strokeStartAnimation.fromValue = percentageElapsedWithSkip
    strokeStartAnimation.toValue = 1
    strokeStartAnimation.duration = CMTimeGetSeconds(duration) - CMTimeGetSeconds(currentTime) - timeToSkip
    strokeStartAnimation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionLinear)

    animationGroup = CAAnimationGroup()
    animationGroup.duration = CMTimeGetSeconds(duration) - CMTimeGetSeconds(currentTime) - timeToSkip
    animationGroup.animations = [strokeStartAnimation]
    externalCircle.addAnimation(animationGroup, forKey: "animationGroup")

}

在CABasicAnimation（iOS）中向前略

2 个答案: