Question

当我使用UIModalPresentationOverCurrentContext模式演示样式时，如何确定隐藏或显示父视图控制器的时间？在正常情况下，我可以使用viewWillAppear:和viewWillDisappear:，但他们似乎没有对此进行解雇。

Answer 1

UIModalPresentationOverCurrentContext 旨在用于在当前viewController上显示内容。这意味着，如果在parentViewController中有动画或视图更改，如果视图是透明的，您仍然可以通过childViewController查看。因此，它还意味着对于当前上下文的视图，视图永远不会消失。似乎合法的是 viewWillAppear：，viewDidAppear：，viewWillDisappear：和viewDidDisappear 不会被调用。

但是，您可以使用 UIModalPresentationStyle.Custom 在当前上下文中显示完全相同的行为。您不会收到视图外观回调，但您可以创建自己的自定义 UIPresentationController 来获取这些回调。

以下是一个示例实现，

class MyFirstViewController: UIViewController {

            ....

    func presentNextViewController() {
        let myNextViewController = MyNextViewController()

        myNextViewController.modalPresentationStyle = UIModalPresentationStyle.Custom
        myNextViewController.transitioningDelegate = self
        presentViewController(myNextViewController, animated: true) { _ in

        }
    }

               ...
}

extension MyFirstViewController: UIViewControllerTransitioningDelegate {

    func presentationControllerForPresentedViewController(presented: UIViewController, presentingViewController presenting: UIViewController, sourceViewController source: UIViewController) -> UIPresentationController?
    {
        let customPresentationController = MyCustomPresentationController(presentedViewController: presented, presentingViewController: presenting)
        customPresentationController.appearanceDelegate = self
        return customPresentationController
    }
}

extension MyFirstViewController: MyCustomApprearanceDelegate {

    func customPresentationTransitionWillBegin() {
        print("presentationWillBegin")
    }

    func customPresentationTransitionDidEnd() {
        print("presentationDidEnd")
    }

    func customPresentationDismissalWillBegin() {
        print("dismissalWillBegin")
    }

    func customPresentationDismissalDidEnd() {
        print("dismissalDidEnd")
    }
}




protocol MyCustomApprearanceDelegate: class {
    func customPresentationTransitionWillBegin()
    func customPresentationTransitionDidEnd()
    func customPresentationDismissalWillBegin()
    func customPresentationDismissalDidEnd()
}

class MyCustomPresentationController: UIPresentationController {

    weak var appearanceDelegate: MyCustomApprearanceDelegate!

    override init(presentedViewController: UIViewController, presentingViewController: UIViewController) {
        super.init(presentedViewController: presentedViewController, presentingViewController: presentingViewController)
    }

    override func presentationTransitionWillBegin() {
        appearanceDelegate.customPresentationTransitionWillBegin()
    }

    override func presentationTransitionDidEnd(completed: Bool) {
        appearanceDelegate.customPresentationTransitionDidEnd()
    }

    override func dismissalTransitionWillBegin() {
        appearanceDelegate.customPresentationDismissalWillBegin()
    }

    override func dismissalTransitionDidEnd(completed: Bool) {
        appearanceDelegate.customPresentationDismissalDidEnd()
    }
}

在UIModalPresentationOverCurrentContext上查看控制器生命周期

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