<UIViewController> 开始/结束外观转换的不平衡调用

Posted 2023-03-11

【中文标题】<UIViewController> 开始/结束外观转换的不平衡调用

【英文标题】：Unbalanced calls to begin/end appearance transitions for <UIViewController>

【发布时间】：2014-03-27 02:07:45

【问题描述】：

基于Apple documentation，我想出了以下方法来在收容控制器中的控制器之间切换。当有oldC 时，我会在控制台上收到Unbalanced calls to begin/end appearance transitions for <...>。

- (void) showController:(UIViewController*)newC withView:(UIView*)contentView animated:(BOOL)animated

    UIViewController *oldC = self.childViewControllers.firstObject;
    if (oldC == newC) 
        return;
    

    [oldC willMoveToParentViewController:nil];

    [self addChildViewController:newC];
    newC.view.frame = (CGRect) 0, 0, contentView.frame.size ;
    [contentView addSubview:newC.view];

    if (animated && oldC != nil) 
        oldC.view.alpha = 1.0f;
        newC.view.alpha = 0.0f;
        [self transitionFromViewController:oldC toViewController:newC duration:0.25f options:0 animations:^

            oldC.view.alpha = 0.0f;
            newC.view.alpha = 1.0f;

          completion:^(BOOL finished) 
            [oldC removeFromParentViewController];
            [newC didMoveToParentViewController:self];
         ];
     else 
        oldC.view.alpha = 0.0f;
        newC.view.alpha = 1.0f;
        [oldC removeFromParentViewController];
        [newC didMoveToParentViewController:self];
    

我是这样称呼它的：

- (IBAction) buttonSignIn:(id)sender

    [self showController:self.signInViewController withView:self.contentView animated:(sender != nil)];


- (IBAction) buttonSignUp:(id)sender

    [self showController:self.signUpViewController withView:self.contentView animated:(sender != nil)];

为了追踪这一点，我正在记录外观转换

-(void)beginAppearanceTransition:(BOOL)isAppearing animated:(BOOL)animated

    [super beginAppearanceTransition:isAppearing animated:animated];
    NSLog(@"**begin %@", self);


-(void)endAppearanceTransition

    [super endAppearanceTransition];
    NSLog(@"**end** %@", self);

这是日志的样子：

] **begin <SignInViewController: 0x10c769a20>
] **begin <SignUpViewController: 0x10c768770>
] Unbalanced calls to begin/end appearance transitions for <SignUpViewController: 0x10c768770>.
] **end** <SignUpViewController: 0x10c768770>
] **end** <SignInViewController: 0x10c769a20>

现在我有点困惑。这里有什么问题？

【参考方案1】：

原来transitionFromViewController:toViewController:duration:options:animations:completion: 也添加了视图。

此方法将第二个视图控制器的视图添加到视图层次结构中，然后执行动画块中定义的动画。动画完成后，它会从视图层次结构中移除第一个视图控制器的视图。

这意味着addSubview需要相应调整。

- (void) showController:(UIViewController*)newC withView:(UIView*)contentView animated:(BOOL)animated

    UIViewController *oldC = self.childViewControllers.firstObject;
    if (oldC == newC) 
        return;
    

    [oldC willMoveToParentViewController:nil];

    [self addChildViewController:newC];
    newC.view.frame = (CGRect) 0, 0, contentView.frame.size ;

    if (animated && oldC != nil) 
        oldC.view.alpha = 1.0f;
        newC.view.alpha = 0.0f;
        [self transitionFromViewController:oldC toViewController:newC duration:0.25f options:0 animations:^

            oldC.view.alpha = 0.0f;
            newC.view.alpha = 1.0f;

          completion:^(BOOL finished) 
            [oldC removeFromParentViewController];
            [newC didMoveToParentViewController:self];
         ];
     else 
        [contentView addSubview:newC.view];
        oldC.view.alpha = 0.0f;
        newC.view.alpha = 1.0f;
        [oldC removeFromParentViewController];
        [newC didMoveToParentViewController:self];
    

【讨论】：

我尝试了 tcurdt 建议的一切。经过几个小时的努力，我终于成功了。 tcurdt 你是天才！

如果您不想制作动画，可以安全地传递duration:0：developer.apple.com/library/ios/documentation/UIKit/Reference/…：

谢谢，你拯救了我的一天

【参考方案2】：

旧代码

[self addChildViewController:toVC];
[fromVC willMoveToParentViewController:nil];
[self.view addSubview:toVC.view];
[toVC.view mas_makeConstraints:^(MASConstraintMaker *make) 
    make.edges.mas_equalTo(0);
 ];

 [self transitionFromViewController:fromVC
                      toViewController:toVC duration:0
                               options:UIViewAnimationOptionTransitionNone
                            animations:^
                             completion:^(BOOL finished) 
                                [fromVC.view removeFromSuperview];
                                [fromVC removeFromParentViewController];
                                [toVC didMoveToParentViewController:self];
                                self.currentVC = toVC;
                            ];

新代码，没关系

[self addChildViewController:toVC];
[fromVC willMoveToParentViewController:nil];

    [self transitionFromViewController:fromVC
                      toViewController:toVC duration:0
                               options:UIViewAnimationOptionTransitionNone
                            animations:^
                             completion:^(BOOL finished) 
                                [fromVC.view removeFromSuperview];
                                [fromVC removeFromParentViewController];
                                [toVC didMoveToParentViewController:self];
                                self.currentVC = toVC;
                            ];

【参考方案3】：

我将持续时间设置为 0，这意味着 animation:NO 用于 transitionFromViewControllercall。