当调用`presentViewController：`时，UIAlertController被移动到屏幕顶部的错误位置-Java 学习之路

从 UIAlertController 呈现视图会将警报移动到屏幕左上角的错误位置 . iOS 8.1，设备和模拟器 .

当我们尝试从当前“最顶层”视图中呈现视图时，我们在应用程序中注意到了这一点 . 如果UIAlertController恰好是最顶层的视图，我们会得到这种行为 . 我们已经更改了我们的代码以简单地忽略UIAlertControllers，但我发布这个以防其他人遇到同样的问题（因为我找不到任何东西） .

我们已将此分离为一个简单的测试项目，该问题底部的完整代码 .

在新的Single View Xcode项目中的View Controller上实现 viewDidAppear: .
提出 UIAlertController 警报 .
警报控制器立即调用 presentViewController:animated:completion: 显示然后关闭另一个视图控制器：

presentViewController:... 动画开始的那一刻，UIAlertController被移动到屏幕的左上角：

Alert has moved to top of screen

当 dismissViewControllerAnimated: 动画结束时，警报已进一步移动到屏幕的左上边缘：

Alert has moved into the top-left margin of the screen

完整代码：

- (void)viewDidAppear:(BOOL)animated {
    // Display a UIAlertController alert
    NSString *message = @"This UIAlertController will be moved to the top of the screen if it calls `presentViewController:`";
    UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"UIAlertController iOS 8.1" message:message preferredStyle:UIAlertControllerStyleAlert];
    [alert addAction:[UIAlertAction actionWithTitle:@"I think that's a Bug" style:UIAlertActionStyleCancel handler:nil]];
    [self presentViewController:alert animated:YES completion:nil];

    // The UIAlertController should Present and then Dismiss a view
    UIViewController *viewController = [[UIViewController alloc] init];
    viewController.view.backgroundColor = self.view.tintColor;
    [alert presentViewController:viewController animated:YES completion:^{
        dispatch_after(0, dispatch_get_main_queue(), ^{
            [viewController dismissViewControllerAnimated:YES completion:nil];
        });
    }];

    // RESULT:
    // UIAlertController has been moved to the top of the screen.
    // http://i.imgur.com/KtZobuK.png
}

上面的代码中是否有任何导致此问题的内容？是否存在任何可以从UIAlertController无错误地呈现视图的替代方案？

rdar：// 19037589
http://openradar.appspot.com/19037589

8 回答

1

rdar://19037589被Apple关闭

Apple开发者关系| 25-Feb-2015 10:52 AM没有计划根据以下内容解决此问题：不支持此功能，请避免在UIAlertController上展示 . 我们现在正在结束这份报告 . 如果您对解决方案有疑问，或者这对您来说仍然是一个关键问题，请使用该信息更新您的错误报告 . 对于可能影响此问题的任何更新，请务必定期检查新的Apple版本 .

回复于 2024-05-14T11:50:33+08:00
9
我遇到过一种情况，有时模态视图会出现在警报之上（愚蠢的情况，我知道），而UIAlertController可能出现在左上方（如2nd screenshot of the original question），我找到了一个单行解决方案，似乎工作 . 对于即将在UIAlertController上呈现的控制器，更改其模式表示样式，如下所示：
```
viewControllerToBePresented.modalPresentationStyle = .OverFullScreen
```
这应该在您致电 presentViewController(_ viewControllerToPresent: UIViewController, animated flag: Bool, completion completion: (() -> Void)?) 之前完成
回复于 2024-05-14T11:50:33+08:00

这有点令人失望......将警报移动到UIViewControllers，但随后禁止对它们进行常规使用 . 我在一个类似的应用程序上工作 - 它有时需要跳转到一个新的用户上下文，并且这样做会在那里提供一个新的视图控制器 . 实际上，警报是视图控制器在这种情况下几乎更好，因为它们将被保留 . 但是现在我们已经切换到UIViewControllers，我们看到相同的位移 .

我们可能必须提出一个不同的解决方案（可能使用不同的窗口），如果顶级是UIAlertController，我们可能会避免显示 . 但是，可以恢复正确的定位 . 这可能不是一个好主意，因为如果Apple改变了他们的屏幕定位，代码可能会破坏，但是如果非常需要这个功能，则下面的子类似乎可以工作（在iOS8中） .

@interface MyAlertController : UIAlertController
@end

@implementation MyAlertController
/*
 * UIAlertControllers (of alert type, and action sheet type on iPhones/iPods) get placed in crazy
 * locations when you present a view controller over them.  This attempts to restore their original placement.
 */
- (void)_my_fixupLayout
{
    if (self.preferredStyle == UIAlertControllerStyleAlert && self.view.window)
    {
        CGRect myRect = self.view.bounds;
        CGRect windowRect = [self.view convertRect:myRect toView:nil];
        if (!CGRectContainsRect(self.view.window.bounds, windowRect) || CGPointEqualToPoint(windowRect.origin, CGPointZero))
        {
            CGPoint center = self.view.window.center;
            CGPoint myCenter = [self.view.superview convertPoint:center fromView:nil];
            self.view.center = myCenter;
        }
    }
    else if (self.preferredStyle == UIAlertControllerStyleActionSheet && self.traitCollection.userInterfaceIdiom == UIUserInterfaceIdiomPhone && self.view.window)
    {
        CGRect myRect = self.view.bounds;
        CGRect windowRect = [self.view convertRect:myRect toView:nil];
        if (!CGRectContainsRect(self.view.window.bounds, windowRect) || CGPointEqualToPoint(windowRect.origin, CGPointZero))
        {
            UIScreen *screen = self.view.window.screen;
            CGFloat borderPadding = ((screen.nativeBounds.size.width / screen.nativeScale) - myRect.size.width) / 2.0f;
            CGRect myFrame = self.view.frame;
            CGRect superBounds = self.view.superview.bounds;
            myFrame.origin.x = CGRectGetMidX(superBounds) - myFrame.size.width / 2;
            myFrame.origin.y = superBounds.size.height - myFrame.size.height - borderPadding;
            self.view.frame = myFrame;
        }
    }
}

- (void)viewWillLayoutSubviews
{
    [super viewWillLayoutSubviews];
    [self _my_fixupLayout];
}

@end

Apple可能会认为视图定位是私有的，因此以这种方式恢复它可能不是最好的主意，但它现在可以使用 . 也许可以在-presentViewController：animated：的覆盖中存储旧框架，并简单地恢复它而不是重新计算 .

可以调整UIAlertController本身来完成与上面相同的操作，这也包括你无法控制的代码所呈现的UIAlertControllers，但我更喜欢只在那些苹果要修复的bug的地方使用swizzles（因此有是一个可以删除混合的时代，我们允许现有的代码“正常工作”，而不是为了解决错误而解决问题） . 但是，如果这是苹果公司不会解决的问题（如他们的回复所示，如此处的另一个答案所述），那么通常有一个单独的类来修改行为更安全，因此您只在已知情况下使用它 .

回复于 2024-05-14T11:50:33+08:00

我认为你应该像这样对UIAlertController进行分类：

@implementation UIAlertController(UIAlertControllerExtended)

- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];

    if (self.preferredStyle == UIAlertControllerStyleAlert) {
        __weak UIAlertController *pSelf = self;

        dispatch_async(dispatch_get_main_queue(), ^{
            CGRect screenRect = [[UIScreen mainScreen] bounds];
            CGFloat screenWidth = screenRect.size.width;
            CGFloat screenHeight = screenRect.size.height;

            [pSelf.view setCenter:CGPointMake(screenWidth / 2.0, screenHeight / 2.0)];
            [pSelf.view setNeedsDisplay];
        });
    }
}

@end

回复于 2024-05-14T11:50:33+08:00

我也有这个问题 . 如果我在呈现UIAlertController时呈现了一个视图控制器，则警报将转到左上角 .

我的修复是刷新UIAlertController视图的中心viewDidLayoutSubviews;通过子类化UIAlertController实现 .

class MyBetterAlertController : UIAlertController {

    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()

        let screenBounds = UIScreen.mainScreen().bounds

        if (preferredStyle == .ActionSheet) {
            self.view.center = CGPointMake(screenBounds.size.width*0.5, screenBounds.size.height - (self.view.frame.size.height*0.5) - 8)
        } else {
            self.view.center = CGPointMake(screenBounds.size.width*0.5, screenBounds.size.height*0.5)
        }
    }
}

回复于 2024-05-14T11:50:33+08:00

除了Carl Lindberg's answer还有两种情况也应该考虑在内：

设备旋转
警报内有文本字段时的键盘高度

那么，对我有用的完整答案：

// fix for rotation

-(void)viewWillTransitionToSize:(CGSize)size withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator
{
    [super viewWillTransitionToSize:size withTransitionCoordinator:coordinator];
    [coordinator animateAlongsideTransition:^(id<UIViewControllerTransitionCoordinatorContext> context) {
    } completion:^(id<UIViewControllerTransitionCoordinatorContext> context) {
        [self.view setNeedsLayout];
    }];
}

// fix for keyboard

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillShow:) name:UIKeyboardWillShowNotification object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillHide:) name:UIKeyboardWillHideNotification object:nil];
}

-(void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardWillShowNotification object:nil];
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardWillHideNotification object:nil];
}

- (void)dealloc
{
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}

- (void)keyboardWillShow:(NSNotification *)notification
{
    NSDictionary *keyboardUserInfo = [notification userInfo];
    CGSize keyboardSize = [[keyboardUserInfo objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue].size;
    self.keyboardHeight = keyboardSize.height;
    [self.view setNeedsLayout];
}

- (void)keyboardWillHide:(NSNotification *)notification
{
    self.keyboardHeight = 0;
    [self.view setNeedsLayout];
}

// position layout fix

-(void)viewDidLayoutSubviews
{
    [super viewDidLayoutSubviews];
    [self fixAlertPosition];
}

-(void)fixAlertPosition
{
    if (self.preferredStyle == UIAlertControllerStyleAlert && self.view.window)
    {
        CGRect myRect = self.view.bounds;
        CGRect windowRect = [self.view convertRect:myRect toView:nil];
        if (!CGRectContainsRect(self.view.window.bounds, windowRect) || CGPointEqualToPoint(windowRect.origin, CGPointZero))
        {
            CGRect myFrame = self.view.frame;
            CGRect superBounds = self.view.superview.bounds;
            myFrame.origin.x = CGRectGetMidX(superBounds) - myFrame.size.width / 2;
            myFrame.origin.y = (superBounds.size.height - myFrame.size.height - self.keyboardHeight) / 2;
            self.view.frame = myFrame;
        }
    }
    else if (self.preferredStyle == UIAlertControllerStyleActionSheet && self.traitCollection.userInterfaceIdiom == UIUserInterfaceIdiomPhone && self.view.window)
    {
        CGRect myRect = self.view.bounds;
        CGRect windowRect = [self.view convertRect:myRect toView:nil];
        if (!CGRectContainsRect(self.view.window.bounds, windowRect) || CGPointEqualToPoint(windowRect.origin, CGPointZero))
        {
            UIScreen *screen = self.view.window.screen;
            CGFloat borderPadding = ((screen.nativeBounds.size.width / screen.nativeScale) - myRect.size.width) / 2.0f;
            CGRect myFrame = self.view.frame;
            CGRect superBounds = self.view.superview.bounds;
            myFrame.origin.x = CGRectGetMidX(superBounds) - myFrame.size.width / 2;
            myFrame.origin.y = superBounds.size.height - myFrame.size.height - borderPadding;
            self.view.frame = myFrame;
        }
    }
}

此外，如果使用类别，则需要以某种方式存储键盘高度，如下所示：

@interface UIAlertController (Extended)

@property (nonatomic) CGFloat keyboardHeight;

@end

@implementation UIAlertController (Extended)

static char keyKeyboardHeight;

- (void) setKeyboardHeight:(CGFloat)height {
    objc_setAssociatedObject (self,&keyKeyboardHeight,@(height),OBJC_ASSOCIATION_RETAIN);
}

-(CGFloat)keyboardHeight {
    NSNumber *value = (id)objc_getAssociatedObject(self, &keyKeyboardHeight);
    return value.floatValue;
}

@end

回复于 2024-05-14T11:50:33+08:00

-2
用户 manoj.agg 将此答案发布到了Open Radar bug report，但是说：

不知何故，我没有足够的声誉在Stackoverflow上发布答案 .

在这里发布他的答案为后代 . 我没有测试/评估它 .

Step 1:

创建一个继承自 UIViewController 的自定义View Controller并实现 UIPopoverPresentationControllerDelegate ：
```
@interface CustomUIViewController : UIViewController<UITextFieldDelegate, UIPopoverPresentationControllerDelegate>
```
Step 2:

全屏显示视图，使用演示文稿popover：
```
CustomUIViewController *viewController = [[CustomUIViewController alloc] init];
viewController.view.backgroundColor = self.view.tintColor;
viewController.modalPresentationStyle = UIModalPresentationOverFullScreen;

UIPopoverPresentationController *popController = viewController.popoverPresentationController;
popController.delegate = viewController;

[alert presentViewController:viewController animated:YES completion:^{
    dispatch_after(0, dispatch_get_main_queue(), ^{
        [viewController dismissViewControllerAnimated:YES completion:nil];
    });
}];
```
我遇到了类似的问题，其中密码输入视图需要显示在任何其他视图控制器的顶部，包括UIAlertControllers . 上面的代码帮助我解决了这个问题 . iOS 8中值得注意的变化是 UIAlertController 继承自 UIViewController ，而 UIAlertView 则不然 .
回复于 2024-05-14T11:50:33+08:00

var kbHeight: CGFloat = 0    

override func keyboardWillShow(_ notification: Notification) {
    if let userInfo = notification.userInfo {
        if let keyboardSize =  (userInfo[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue {
            kbHeight = keyboardSize.height
            self.animateTextField(up: true)
        }
    }
}

override func keyboardWillHide(_ notification: Notification) {
      self.animateTextField(up: false)
}


func animateTextField(up: Bool) {
    let movement = (up ? -kbHeight : kbHeight)
    UIView.animate(withDuration: 0.3, animations: {
        self.view.frame =  CGRect.offsetBy(self.view.frame)(dx: 0, dy: movement)
    })
}

回复于 2024-05-14T11:50:33+08:00

当调用`presentViewController：`时，UIAlertController被移动到屏幕顶部的错误位置

8 回答

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