如何防止源视图控制器在推送后消失？

Question

首先，这是我的视图控制器/segue 设置：

最右边的三个视图控制器的背景视图是 UIVisualEffectViews，通过它应该可以看到源视图控制器。它们被添加到各种viewDidLoad()s 中，如下所示：

let blurEffect = UIBlurEffect(style: .dark)
let blurEffectView = UIVisualEffectView(effect: blurEffect)
blurEffectView.frame = self.view.bounds
blurEffectView.autoresizingMask = [.flexibleWidth, .flexibleHeight]

self.tableView.backgroundView = blurEffectView

现在，主视图控制器（“垃圾日”之一）通过设置视图控制器可见，但只要两个最右边的 VC 之一完全显示在屏幕上，设置 VC 就会消失。这是一个屏幕录像：

Screen recording of the source view controller dis- and reappearing

（请忽略故障，我用来上传此视频的应用程序显然损坏了视频）

我明白了，从技术上讲，Show segue 没有“Over Current Context”的东西，因此，我不应该期望源 VC 不会消失，但必须有一种方法可以在没有自定义的情况下完成这项工作继续。

Answer 1

我建议您在视图控制器之间创建自定义转换。

我刚刚编写并测试了这个类：

class AnimationController: NSObject, UIViewControllerAnimatedTransitioning
{
    var pushing = true

    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
        return 0.3
    }

    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        let duration = transitionDuration(using: transitionContext)

        let toVc = transitionContext.viewController(forKey: .to)!
        let toView = transitionContext.view(forKey: .to)!

        let fromView = transitionContext.view(forKey: .from)!

        let container = transitionContext.containerView

        if pushing {
            container.addSubview(fromView)
            container.addSubview(toView)
        }

        var finalFrame = transitionContext.finalFrame(for: toVc)
        if pushing {
            finalFrame.origin.x = finalFrame.width
            toView.frame = finalFrame
            finalFrame.origin.x = 0
        } else {
            finalFrame.origin.x = finalFrame.width
        }

        UIView.animate(withDuration: duration, delay: 0, options: .curveEaseOut, animations: {
            if self.pushing {
                toView.frame = finalFrame
            } else {
                fromView.frame = finalFrame
            }
        }) { (_) in
            transitionContext.completeTransition(true)
            if self.pushing {
                container.insertSubview(fromView, belowSubview: toView)
            } else {
                fromView.removeFromSuperview()
            }
        }
    }
}

在您的 UINavigationController 类中执行以下操作：

class NavigationController: UINavigationController {

    let animationController = AnimationController()

    override func viewDidLoad() {
        super.viewDidLoad()

        delegate = self
    }
}

还有这个扩展：

extension NavigationController: UINavigationControllerDelegate
{
    func navigationController(_ navigationController: UINavigationController, animationControllerFor operation: UINavigationControllerOperation, from fromVC: UIViewController, to toVC: UIViewController) -> UIViewControllerAnimatedTransitioning? {

        animationController.pushing = operation == .push

        return animationController
    }
}

但是，这会使您失去交互式关闭手势（从屏幕左侧滑动以关闭）因此您需要自己修复。