willMoveToWindow被调用两次

Question

我正在冲洗willMoveToWindow:，遇到了一个问题，它在视图上被调用了两次。

当新的视图控制器被推到UINavigationController上时，

在具有nil值的现有视图上调用willMoveToWindow:（这很有意义，因为视图正在移动到屏幕外）

在那之后，方法willMoveToWindow:再次被调用，但现在使用原始窗口。

我最初的想法是，在原始方法启动之前快速调用window属性

为了安全起见，我创建了一个小样本项目，并确认了相同的行为。

基本上，我需要一种方法来确定视图不在window上（因为当视图移动到实际上不应该运行（至少不应该运行两次）的窗口时，我正在触发逻辑）

为了参考，可以用以下代码重现问题：

  @implementation RandomView
    -(void)willMoveToWindow:(UIWindow *)newWindow {
    // when the new view controller is pushed - 
    //the method is called twice on the existing view (on the screen view)- 
    //first time will be called with nil - 
    //second time with the original window
        NSLog(@"********%s <RandomView %p> <Window %p>",__PRETTY_FUNCTION__,self,newWindow);
    }
    -(void)didMoveToWindow {
        NSLog(@"********%s <RandomView %p> <Window %p>",__PRETTY_FUNCTION__,self,self.window);
    }
    @end
    @implementation ViewController
    - (void)viewDidLoad {
        [super viewDidLoad];
        RandomView *k = [[RandomView alloc] initWithFrame:self.view.bounds];
        [self.view addSubview:k];
    }

    -(void)viewDidAppear:(BOOL)animated {
        [super viewDidAppear:animated];
        static dispatch_once_t onceToken;
        dispatch_once(&onceToken, ^{
            dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(1 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
                ViewController *vc = [[ViewController alloc] init];
                [self.navigationController pushViewController:vc animated:YES];
            });
        });
        //[self becomeFirstResponder];
    }
    @end

编辑控制台

    [RandomView willMoveToWindow:] <RandomView 0x7f8b21e16630> <Window 0x7f8b21d220d0>
    [RandomView didMoveToWindow] <RandomView 0x7f8b21e16630> <Window 0x7f8b21d220d0>
  //THIS IS THE ISSUE
    [RandomView willMoveToWindow:] <RandomView 0x7f8b21e16630> <Window 0x0>
    [RandomView didMoveToWindow] <RandomView 0x7f8b21e16630> <Window 0x0>
    [RandomView willMoveToWindow:] <RandomView 0x7f8b21e16630> <Window 0x7f8b21d220d0>
    [RandomView didMoveToWindow] <RandomView 0x7f8b21e16630> <Window 0x7f8b21d220d0>
    [RandomView willMoveToWindow:] <RandomView 0x7f8b21e16630> <Window 0x0>
    [RandomView didMoveToWindow] <RandomView 0x7f8b21e16630> <Window 0x0>

Answer 1

我也面临同样的问题

但是在通过响应器链查找视图层次结构之后，会有一个小的不同的can检查。我不确定这是否安全。

但我认为苹果的动画代码顺序不对，如果他们先将动画视图添加到窗口中，willMoveToWindow:就不会调用两次。

2017-03-08 22:49:35.167 view[36189:410065] show
0x7fa9c36059f0,MyView
0x7fa9c3407cb0,UIView
0x7fa9c340b9d0,ViewController
0x7fa9c3403c50,UIViewControllerWrapperView
0x7fa9c340ee90,UINavigationTransitionView
0x7fa9c5802d10,UILayoutContainerView
0x7fa9c381ee00,UINavigationController
0x7fa9c3609c40,UIWindow
0x7fa9c3400020,UIApplication
0x608000038900,AppDelegate
2017-03-08 22:49:54.501 view[36189:410065] hide
0x7fa9c36059f0,MyView
0x7fa9c3407cb0,UIView
0x7fa9c340b9d0,ViewController
0x7fa9c3500bd0,UIView  <----- not real hide
2017-03-08 22:49:54.501 view[36189:410065] show
0x7fa9c36059f0,MyView
0x7fa9c3407cb0,UIView
0x7fa9c340b9d0,ViewController
0x7fa9c3500bd0,UIView
0x7fa9c3403c50,UIViewControllerWrapperView
0x7fa9c340ee90,UINavigationTransitionView
0x7fa9c5802d10,UILayoutContainerView
0x7fa9c381ee00,UINavigationController
0x7fa9c3609c40,UIWindow
0x7fa9c3400020,UIApplication
0x608000038900,AppDelegate
2017-03-08 22:49:54.501 view[36189:410065] show
0x7fa9c35062f0,MyView
0x7fa9c3505ae0,UIView
0x7fa9c58030c0,ViewController
0x7fa9c3506c10,_UIParallaxDimmingView
0x7fa9c35022c0,UIView
0x7fa9c3403c50,UIViewControllerWrapperView
0x7fa9c340ee90,UINavigationTransitionView
0x7fa9c5802d10,UILayoutContainerView
0x7fa9c381ee00,UINavigationController
0x7fa9c3609c40,UIWindow
0x7fa9c3400020,UIApplication
0x608000038900,AppDelegate
2017-03-08 22:49:55.037 view[36189:410065] hide
0x7fa9c36059f0,MyView
0x7fa9c3407cb0,UIView
0x7fa9c340b9d0,ViewController  <----- real hide