UIAlertController is moved to buggy position at top of screen when it calls `presentViewController:`

Question

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 h

Answer 1

EDIT: Tested in 2020, Xcode 11.2, iOS 13

If anyone still looking for a better answer to this, then here is my solution. Use updateConstraints method to readjust the constraints.

your_alert_controller_obj.updateConstraints()

Answer 2

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)
    })
}

Answer 3

I encountered a situation where sometimes a modal view would present itself on top of a an alert (silly situation, I know), and the UIAlertController could appear in the top left (like the 2nd screenshot of the original question), and I found a one-liner solution that seems to work. For the controller that's about to be presented on the UIAlertController, change its modal presentation style like so:

viewControllerToBePresented.modalPresentationStyle = .OverFullScreen

This should be done just before you call presentViewController(_ viewControllerToPresent: UIViewController, animated flag: Bool, completion completion: (() -> Void)?)

Answer 4

A quick fix is to always present the View Controller on top of a new UIWindow:

UIWindow *window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
window.rootViewController = [[UIViewController alloc] init];
window.windowLevel = UIWindowLevelNormal;
[window makeKeyAndVisible];
[window.rootViewController presentViewController: viewController
                                        animated:YES 
                                      completion:nil];

Answer 5

I think that you only should to categorize UIAlertController like this:

@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

Answer 6

I was having this issue as well. If I presented a view controller while a UIAlertController was presented, the alert would go to the top left.

My fix is to refresh the center of the UIAlertController's view in viewDidLayoutSubviews; achieved by subclassing UIAlertController.

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)
        }
    }
}