[英]Drag-to-dismiss interactive transition out of sync with pan gesture
我正在尝试使用UIViewControllerAnimatedTransitioning
和UIPercentDrivenInteractiveTransition
来实现自定义的拖放交互过渡。
这是用于解散的动画师代码,它只是将视图从框架中完全向下移动:
final class SheetDismissAnimator: NSObject, UIViewControllerAnimatedTransitioning {
func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
0.5
}
func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
guard let fromVC = transitionContext.viewController(forKey: .from) else { return }
UIView.animate(withDuration: transitionDuration(using: transitionContext), animations: {
fromVC.view.frame.origin.y = transitionContext.containerView.frame.height
}, completion: { _ in
transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
})
}
}
这是我试图关闭的模态视图控制器的代码,它附加了平移手势识别器:
final class ModalViewController: UIViewController {
private let customTransitionDelegate = SheetTransitioningDelegate()
private var interactionController: UIPercentDrivenInteractiveTransition?
init() {
super.init(nibName: nil, bundle: nil)
modalPresentationStyle = .custom
transitioningDelegate = customTransitionDelegate
}
required init?(coder: NSCoder) {
super.init(coder: coder)
}
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = .red
view.addGestureRecognizer(UIPanGestureRecognizer(target: self, action: #selector(handleGesture(_:))))
}
@objc func handleGesture(_ gesture: UIPanGestureRecognizer) {
let translate = gesture.translation(in: view)
let percent = translate.y / view.bounds.height
switch gesture.state {
case .began:
interactionController = UIPercentDrivenInteractiveTransition()
customTransitionDelegate.interactionController = interactionController
dismiss(animated: true)
case .changed:
interactionController?.update(percent)
case .cancelled:
interactionController?.cancel()
case .ended:
let velocity = gesture.velocity(in: gesture.view)
if percent > 0.5 || velocity.y > 700 {
interactionController?.finish()
} else {
interactionController?.cancel()
}
interactionController = nil
default:
break
}
}
}
我相信相关部分是handleGesture(_ gesture: UIPanGestureRecognizer)
函数,它计算推进动画的百分比。 为了清楚起见,粘贴了整个代码。
我希望动画线性地跟随平移手势,但这是发生的事情:
我通过切换到UIViewPropertyAnimator
解决了这个问题:
final class SheetDismissAnimator: NSObject, UIViewControllerAnimatedTransitioning {
func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
0.5
}
func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
let propertyAnimator = UIViewPropertyAnimator(duration: transitionDuration(using: transitionContext),
timingParameters: UISpringTimingParameters(dampingRatio: 1))
propertyAnimator.addAnimations {
switch self.type {
case .presented:
guard let toVC = transitionContext.viewController(forKey: .to) else { break }
toVC.view.frame = transitionContext.finalFrame(for: toVC)
case .dismissed:
transitionContext.view(forKey: .from)?.frame.origin.y = transitionContext.containerView.frame.maxY
}
}
propertyAnimator.addCompletion { _ in
transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
}
propertyAnimator.startAnimation()
}
}
我还在我的手势处理代码中添加了以下内容,这是将手势速度转换为动画速度的基本尝试。
case .ended:
if percent > 0.45 || velocity.y > 700 {
interactor.timingCurve = UICubicTimingParameters(animationCurve: .linear)
interactor.completionSpeed = max(1, (view.frame.height * (1 / interactor.duration) / velocity.y))
interactor.finish()
} else {
interactor.cancel()
}
isInteractive = false
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