ios - UIView removeFromSuperview 正在调用 didMoveToSuperview

Question

我不明白为什么 UIView 的 removeFromSuperview 调用 didMoveToSuperview。

我认为 didMoveToSuperview 仅在将 View 添加到 View 时调用。谁能解释为什么 removeFromSuperview 调用 didMoveToSuperview？

这是我在 removeFromSuperview 中所做的:

public override func removeFromSuperview() {

    clearDelegates()

    chaosPad?.removeFromSuperview()
    brushSliders?.removeFromSuperview()
    moodSlider?.removeFromSuperview()
    brushShapeMenu?.removeFromSuperview()
    moodMenu?.removeFromSuperview()
    gravityMenu?.removeFromSuperview()
    rotationMenu?.removeFromSuperview()

    menuGroups = []
    centerButtons = []
    scrollMenuItems = []
    menu?.removeFromSuperview()
    menu = nil

    super.removeFromSuperview()
}

func clearDelegates() {
    chaosPad?.delegate = nil
    viewController = nil
}

这里是显示如何调用 didMoveToSuperview 的调用堆栈:

#0  0x0000000110f39708 in specialized _fatalErrorMessage(StaticString, StaticString, StaticString, UInt) -> () ()
#1  0x000000010b9cb960 in TDTOilistMenuPainting.configureFrames() -> () at /FastDev/TDTPhotoLib/Oilist/Classes/TDTOilistMenuPainting.swift:161
#2  0x000000010b9cb83e in TDTOilistMenuPainting.didMoveToSuperview() -> () at /FastDev/TDTPhotoLib/Oilist/Classes/TDTOilistMenuPainting.swift:146
#3  0x000000010b9cb872 in @objc TDTOilistMenuPainting.didMoveToSuperview() -> () ()
#4  0x000000010f5d1db5 in __45-[UIView(Hierarchy) _postMovedFromSuperview:]_block_invoke ()
#5  0x000000010dc87c60 in -[NSISEngine withBehaviors:performModifications:] ()
#6  0x000000010f5d19b1 in -[UIView(Hierarchy) _postMovedFromSuperview:] ()
#7  0x000000010f5cf610 in __UIViewWasRemovedFromSuperview ()
#8  0x000000010f5cf107 in -[UIView(Hierarchy) removeFromSuperview] ()
#9  0x000000010b9c9aba in TDTOilistMenuPainting.removeFromSuperview() -> () at /FastDev/TDTPhotoLib/Oilist/Classes/TDTOilistMenuPainting.swift:73
#10 0x000000010ba6d269 in TDTPaintingViewController.(navigationController(UINavigationController, animationControllerForOperation : UINavigationControllerOperation, fromViewController : UIViewController, toViewController : UIViewController) -> UIViewControllerAnimatedTransitioning?).(closure #2) at /FastDev/TDTPhotoLib/Oilist/Classes/TDTPaintingViewController.swift:2706

Answer 1

这是正常行为。 didMoveToSuperview 会在 View 的父 View 发生更改时被调用，即使它更改为 nil。您可以在该方法中检查父 View 是否为 nil 以确定它是否已添加到其父 View 或从其父 View 中删除，例如:

override func didMoveToSuperview() {
    if let superview = self.superview {
        // the view was added as a subview to superview
    }
    else {
        // the view was removed from its superview
    }
}