iphone - CAAnimation 在滚动出界时停止

Question

我有一个无限旋转的 UIImageView 形式的自定义事件指示器。这个惊人的事件指示器被放置在一个表格单元格中。

动画是这样实现的:

CABasicAnimation* animation = [CABasicAnimation animationWithKeyPath:@"transform.rotation.z"];

animation.fromValue = [NSNumber numberWithFloat:0.0f];
animation.toValue = [NSNumber numberWithFloat: M_PI * 2.0];
animation.duration = 1.0f;
animation.repeatCount = INFINITY;

[self.layer addAnimation:animation forKey:@"SpinAnimation"];

起初，它工作得很好......但是当单元格滚动到表格的边界时，动画停止，我不知道如何重置它....../:

请帮忙...
非常感谢...:)

Answer 1

原因是当prepareForReuse 起作用 或您的应用程序进入后台模式时，rotation.z 键的动画变为零。

考虑手动绘制事件指示器或尝试类似 https://github.com/airbnb/lottie-ios 的方法

下面的方法事件指示器在滚动/单元格/背景模式下运行良好

我尝试了 rotation.z 和一些基于 CAReplicationLayer 的变通方法——在滚动/单元格/背景模式下都失败了

private func drawLoaderCircle() {

    let path = UIBezierPath(arcCenter: loaderViewCenter, radius: loaderCircleRadius, startAngle: 0, endAngle: 2 * .pi, clockwise: true).cgPath

    setupGrapes(endAngle: 310, path: path)
}

private func setupGrapes(endAngle: CGFloat, path: CGPath) {

    let step: CGFloat = 2
    var grapeAnimationDelay: CFTimeInterval = 0

    for i in stride(from: 0, to: endAngle, by: step) {

        let radians = i * .pi / 180

        let x = loaderViewCenter.x + loaderCircleRadius * cos(radians)
        let y = loaderViewCenter.y + loaderCircleRadius * sin(radians)

        let grapeLayer = CAShapeLayer()
        grapeLayer.frame = CGRect(x: 0, y: 0, width: circleWidth + 0.2, height: circleWidth + 0.2)
        grapeLayer.position = CGPoint(x: x, y: y)
        grapeLayer.cornerRadius = grapeLayer.frame.width / 2
        grapeLayer.backgroundColor = loaderColor.cgColor

        grapeAnimationDelay += Double(rotateDuration * Double(step) / 360)
        let rotateGrapeAnimation = CAKeyframeAnimation(keyPath: "position")
        rotateGrapeAnimation.path = path
        rotateGrapeAnimation.beginTime = grapeAnimationDelay
        rotateGrapeAnimation.calculationMode = .linear
        rotateGrapeAnimation.repeatCount = .infinity
        rotateGrapeAnimation.isRemovedOnCompletion = false
        rotateGrapeAnimation.duration = rotateDuration

        grapeLayer.add(rotateGrapeAnimation, forKey: nil)

        progressLayer.addSublayer(grapeLayer)
    }

}