Question

我已经实现了很多视图控制器容器，但完全正确地完成生命周期仍然很棘手。

添加子视图控制器的一般方法看起来很简单：

致电parent.addChildViewController(child)（一次！）
致电child.beginAppearanceTransition(true, animated: …)（可能多次，在true和false之间轮流展开）
将孩子的view添加到父级的视图层次结构中
布置孩子的view
致电child.endAppearanceTransition()（一次！）
致电child.didMoveToParentViewController(parent)（一次！）

现在很少这么简单。例如，父视图控制器本身可能处于转换（viewWillAppear()）中，因此必须延迟步骤5和6，直到父级也完成它的转换（viewDidAppear()）。

情况可能更复杂。你可能不小心忘了打电话。或者孩子忘记拨打super.…()。或者你多次调用一个方法，你不应该再次调用它。（

为了找到这样的bug，我在我的库中调用UIViewController中的所有生命周期方法，以便它在日志中自动报告大量不同的生命周期错误。这就像一个魅力，我在自己的容器中发现了几个问题。但是我也收到了UIKit自己的视图控制器的几个报告，所以我现在质疑我是否真的了解预期的生命周期。

UIViewController.didMoveToParentViewController()的文档例如：

如果要实现自己的容器视图控制器，则必须调用子视图的didMoveToParentViewController:方法转换到新控制器后的控制器完成或，如果没有过渡，请立即拨打电话 addChildViewController:方法。

所以现在对我来说最重要的问题是：

方法willMoveToParentViewController()和didMoveToParentViewController()是否与view(Did|Will)(Appear|Disappear)直接相关？即如上面的文档摘录所述，在子视图控制器的转换完成之前，我不能调用didMoveToParentViewController()。这意味着必须最后调用viewDidDisappear()或viewDidAppear() - viewWillAppear()和viewWillDisappear()。

UIKit似乎就是这样做的（在转换期间调用(will|did)MoveToParentViewController），例如在iPhone上以模仿方式呈现UISplitViewController UINavigationController个孩子的时候：

VIEW CONTROLLER LIFECYCLE BROKEN for <UINavigationController: 0x7cc18a00>

Problem:
    .willMoveToParentViewController() was called unexpectedly during an appearance transition. It must only be called while the view controller is in DidDisappear or DidAppear state.

Possible Causes:
    - the view controller containment implementation of UISplitViewController or one if its parents is broken



VIEW CONTROLLER LIFECYCLE BROKEN for <UINavigationController: 0x7cc18a00>

Problem:
    .didMoveToParentViewController() was called unexpectedly during an appearance transition. It must only be called while the view controller is in DidDisappear or DidAppear state.

Possible Causes:
    - the view controller containment implementation of the parent view controller or one if its parents is broken

当呈现具有文本字段的UIAlertViewController时，错误堆积起来：

VIEW CONTROLLER LIFECYCLE BROKEN for <_UIAlertControllerTextFieldViewController: 0x7dd84bb0>

Problem:
    .willMoveToParentViewController() was called unexpectedly while view controller is in WillMoveToParent state.

Possible Causes:
    - _UIAlertControllerTextFieldViewController or one of its superclasses called super.willMoveToParentViewController() multiple times
    - _UIAlertControllerTextFieldViewController or one of its superclasses called super.willMoveToParentViewController() from within it's .didMoveToParentViewController()
    - the view controller containment implementation of UIAlertController or one if its parents is broken
    - it was already called implicitly by parent.addChildViewController(_UIAlertControllerTextFieldViewController) so you must not call it again



VIEW CONTROLLER LIFECYCLE BROKEN for <UICompatibilityInputViewController: 0x7a99fdb0>

Problem:
    .didMoveToParentViewController(non-nil) was not called after .viewDidAppear() to complete an earlier .willMoveToParentViewController(non-nil).

Possible Causes:
    - the view controller containment implementation of UIInputWindowController is likely broken



VIEW CONTROLLER LIFECYCLE BROKEN for <UICompatibilityInputViewController: 0x7dd67650>

Problem:
    .didMoveToParentViewController(non-nil) was not called after .viewDidAppear() to complete an earlier .willMoveToParentViewController(non-nil).

Possible Causes:
    - the view controller containment implementation of UICompatibilityInputViewController is likely broken

是否有人对如何进行视图控制器遏制有很好的了解？
这些只是UIKit中的错误还是这种行为＆＃34;可以接受＆＃34;？

如果有人对生命周期验证和＆amp;错误报告工作可以查看this file。

如何正确实现View Controller Containers？

0 个答案: