交互式过渡非线性

我正在玩自定义和交互式视图控制器转换，UIPercentDrivenInteractiveTransition。我正在构建一个以模式方式呈现卡片（其他视图控制器）的应用程序。我已经进行了自定义转换UIViewControllerAnimatedTransitioning这使得卡片视图控制器的动画非常类似于标准模型演示风格。

func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
    {...}
    let fullScreenFrame = transitionContext.finalFrame(for: cardVC)
    let offsetFrame = cardVC.view.frame.offsetBy(dx: 0, dy: cardVC.view.frame.height)
    let finalFrame = presenting ? fullScreenFrame : offsetFrame
    cardVC.view.frame = presenting ? offsetFrame : fullScreenFrame
    containerView.addSubview(cardVC.view)

    UIView.animateKeyframes(
        withDuration: transitionDuration(using: transitionContext),
        delay: 0,
        options: UIViewKeyframeAnimationOptions.calculationModeLinear,
        animations: {
            UIView.addKeyframe(
                withRelativeStartTime: 0,
                relativeDuration: 1,
                animations: { [weak self] in
                    guard let strongSelf = self else { return }
                    backgroundView.alpha = strongSelf.presenting ? 1 : 0
            })

            UIView.addKeyframe(
                withRelativeStartTime: 0,
                relativeDuration: 1,
                animations: {
                    cardVC.view.frame = finalFrame
            })
    }, completion: { finished in
        backgroundView.removeFromSuperview()
        gradientView.alpha = 1
        transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
    })
}

然后我使用平移手势识别器以交互方式驱动关闭动画：

func handleGesture(_ gestureRecognizer: UIScreenEdgePanGestureRecognizer) {
        let translation = gestureRecognizer.translation(in: gestureRecognizer.view)
        var progress = (translation.y / (UIScreen.main.bounds.height - 70))
        progress = CGFloat(fminf(fmaxf(Float(progress), 0.0), 1.0))

        switch gestureRecognizer.state {
        case .began:
            interactionInProgress = true
            viewController.dismiss(animated: true, completion: nil)

        case .changed:
            shouldCompleteTransition = progress > 0.35
            update(progress)

        case .cancelled:
            interactionInProgress = false
            cancel()

        case .ended:
            interactionInProgress = false
            if !shouldCompleteTransition {
                cancel()
            } else {
                finish()
            }

        default:
            print("Unsupported")
        }
    }

当我通过向下拖动来关闭所呈现的视图控制器时，它似乎不随手势线性移动。交互控制器似乎正在使用一些 escapeInEaseOut 函数。也许设置UIPercentDrivenInteractiveTransition's timingCurve使过渡线性运行。这可能吗，还是我弄错了什么？

您自己已经为动画提供了默认的缓入-缓出时序曲线，方法是在调用中不将时序曲线设置为任何不同的值UIView.animateKeyframes。即使在互动过程中也是如此。

注意设置动画的options to UIViewKeyframeAnimationOptions.calculationModeLinear does not更改时序曲线（如果这就是您认为在这里要完成的事情）。在线性计算模式关键帧动画中添加线性时序曲线的方法是这样的：

var opts : UIViewKeyframeAnimationOptions = .calculationModeLinear
let opt2 : UIViewAnimationOptions = .curveLinear
opts.insert(UIViewKeyframeAnimationOptions(rawValue:opt2.rawValue))
// and now use `opts` as your `options`