我刚刚创建了一个教程，用于交互式地向下拖动模式以将其关闭。
http://www.thorntech.com/2016/02/ios-tutorial-close-modal-dragging/
一开始我发现这个主题令人困惑，因此本教程将逐步构建此主题。
如果你只想自己运行代码，这里是 repo：
https://github.com/ThornTechPublic/InteractiveModal
这是我使用的方法：
视图控制器
您使用自定义动画覆盖关闭动画。如果用户正在拖动模式，interactor 就会启动。
import UIKit
class ViewController: UIViewController {
let interactor = Interactor()
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if let destinationViewController = segue.destinationViewController as? ModalViewController {
destinationViewController.transitioningDelegate = self
destinationViewController.interactor = interactor
}
}
}
extension ViewController: UIViewControllerTransitioningDelegate {
func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
DismissAnimator()
}
func interactionControllerForDismissal(animator: UIViewControllerAnimatedTransitioning) -> UIViewControllerInteractiveTransitioning? {
interactor.hasStarted ? interactor : .none
}
}
解雇动画师
您创建了一个自定义动画师。这是您在 UIViewControllerAnimatedTransitioning 协议中打包的自定义动画。
import UIKit
class DismissAnimator : NSObject {
let transitionDuration = 0.6
}
extension DismissAnimator : UIViewControllerAnimatedTransitioning {
func transitionDuration(transitionContext: UIViewControllerContextTransitioning?) -> NSTimeInterval {
transitionDuration
}
func animateTransition(transitionContext: UIViewControllerContextTransitioning) {
guard
let fromVC = transitionContext.viewControllerForKey(UITransitionContextFromViewControllerKey),
let toVC = transitionContext.viewControllerForKey(UITransitionContextToViewControllerKey),
let containerView = transitionContext.containerView()
else {
return
}
if transitionContext.transitionWasCancelled {
containerView.insertSubview(toVC.view, belowSubview: fromVC.view)
}
let screenBounds = UIScreen.mainScreen().bounds
let bottomLeftCorner = CGPoint(x: 0, y: screenBounds.height)
let finalFrame = CGRect(origin: bottomLeftCorner, size: screenBounds.size)
UIView.animateWithDuration(
transitionDuration(transitionContext),
animations: {
fromVC.view.frame = finalFrame
},
completion: { _ in
transitionContext.completeTransition(!transitionContext.transitionWasCancelled())
}
)
}
}
交互者
您将UIPercentDrivenInteractiveTransition 子类化，以便它可以充当您的状态机。由于两个 VC 都访问了交互器对象，因此使用它来跟踪平移进度。
import UIKit
class Interactor: UIPercentDrivenInteractiveTransition {
var hasStarted = false
var shouldFinish = false
}
模态视图控制器
这会将平移手势状态映射到交互器方法调用。 translationInView() y 值确定用户是否超过阈值。当平移手势为.Ended 时，交互器要么完成要么取消。
import UIKit
class ModalViewController: UIViewController {
var interactor:Interactor? = nil
@IBAction func close(sender: UIButton) {
dismiss(animated: true)
}
@IBAction func handleGesture(sender: UIPanGestureRecognizer) {
let percentThreshold:CGFloat = 0.3
let translation = sender.translation(in: view)
let verticalMovement = translation.y / view.bounds.height
let downwardMovement = fmaxf(Float(verticalMovement), 0.0)
let downwardMovementPercent = fminf(downwardMovement, 1.0)
let progress = CGFloat(downwardMovementPercent)
guard interactor = interactor else { return }
switch sender.state {
case .began:
interactor.hasStarted = true
dismiss(animated: true)
case .changed:
interactor.shouldFinish = progress > percentThreshold
interactor.update(progress)
case .cancelled:
interactor.hasStarted = false
interactor.cancel()
case .ended:
interactor.hasStarted = false
interactor.shouldFinish ? interactor.finish() :
interactor.cancel()
default:
break
}
}
}