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

问题描述

从提供视图UIAlertController 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。

当我们尝试从当前的最顶层视图呈现视图时，我们在应用中注意到了这一点。如果一个UIAlertController恰好是最顶层的视图，我们得到这个行为。我们已经改变了我们的代码，只是忽略UIAlertControllers，但我发布，以防其他人遇到相同的问题（因为我找不到任何东西）。

1. 实现 viewDidAppear：



2. 提供 UIAlertController 警报。


3. 警报控制器立即调用 presentViewController：animated：completion：显示并关闭另一个视图控制器：

当前 presentViewController：... 动画开始时，UIAlertController被移动到屏幕的左上角：

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

完整代码：

   - （void）viewDidAppear ：（BOOL）animated {
 //显示一个UIAlertController警告
 NSString * message = @如果UIAlertController调用`presentViewController：`，这个UIAlertController将被移动到屏幕的顶部; 
 UIAlertController * alert = [UIAlertController alertControllerWithTitle：@UIAlertController iOS 8.1message：message preferredStyle：UIAlertControllerStyleAlert]; 
 [alert addAction：[UIAlertAction actionWithTitle：@我认为这是一个Bug风格：UIAlertActionStyleCancel handler：nil]]; 
 [self presentViewController：alert animated：YES completion：nil]; 
 
 //存在然后关闭视图
 UIViewController * viewController = [[UIViewController alloc] init]; 
 viewController.view.backgroundColor = self.view.tintColor; 
 [alert presentViewController：viewController animated：YES completed：^ {
 dispatch_after（0，dispatch_get_main_queue（），^ {
 [viewController dismissViewControllerAnimated：YES completion：nil]; 
} ; 
}]; 
 
 //结果：
 // UIAlertController已移动到屏幕顶部。 
 // http://i.imgur.com/KtZobuK.png 
} 
  

上述代码中有什么会导致此问题？是否有任何替代方案可以允许从UIAlertController无错地呈现视图？

rdar：// 19037589

解决方案

被Apple关闭

Presenting a view from a UIAlertController moves the alert to a buggy position at the top-left corner of the screen. iOS 8.1, device and simulator.

We have noticed this in an app when we attempt to present a view from the current "top-most" view. If a UIAlertController happens to be the top-most view we get this behavior. We have changed our code to simply ignore UIAlertControllers, but I'm posting this in case others hit the same issue (as I couldn't find anything).

We have isolated this to a simple test project, full code at the bottom of this question.

1. Implement viewDidAppear: on the View Controller in a new Single View Xcode project.
2. Present aUIAlertController alert.
3. Alert controller immediately calls presentViewController:animated:completion: to display and then dismiss another view controller:

The moment the presentViewController:... animation begins, the UIAlertController is moved to the top-left corner of the screen:

When the dismissViewControllerAnimated: animation ends, the alert has been moved even further into the top-left margin of the screen:

Full code:

- (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];

    // 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
}

Is there anything in the above code that would be causing this issue? Do any alternatives exist that would allow bug-free presentation of a view from a UIAlertController?

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

解决方案

rdar://19037589 was closed by Apple

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