Check if a UIAlertView is showing

Question

I have a method that posts HTTP data and displays a UIAlertView if there is an error. If I have multiple HTTP post I will show multiple UIAlertView for every error.

I want to show a UIAlertView only if is not showing other UIAlertView. How can I determine this?

score 60 · Answer 1 · answered Apr 19 '12 at 12:55

Why not just check the visible property, maintained by the UIAlertView class?

if (_alert) //alert is a retained property
{
    self.alert = [[[UIAlertView alloc] initWithTitle:@"Your Title"
                                             message:@"Your message" 
                                            delegate:self
                                   cancelButtonTitle:@"Cancel"
                                   otherButtonTitles:@"OK"] autorelease];
}
if (!_alert.visible)
{
    [_alert show];
}

From iOS9, the replaced 'UIAlertController' doesn't have the property 'visible'. — KoreanXcodeWorker, Jul 06 '16 at 01:51

score 52 · Accepted Answer · edited Jan 23 '16 at 08:20

52

On the object that calls set an ivar before invoking the show method on your UIAlertView.

...

if (!self.alertShowing) {
    theAlert = [[UIAlertView alloc] initWithTitle:title message:details delegate:self cancelButtonTitle:nil otherButtonTitles:@"Okay", nil];
    self.alertShowing = YES;
    [theAlert show];
}

...

Then in your delegate method for the alert manage setting your flag ivar to no:

- (void)alertView:(UIAlertView *)alertView didDismissWithButtonIndex:(NSInteger)buttonIndex
{
  ...
      self.alertShowing = NO;
}

If you want the alerts to show sequentially, I would post notifications to add each message to a queue and then only take a message off the queue after an alert is dismissed.

edited Jan 23 '16 at 08:20

Kampai

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answered Mar 27 '10 at 14:27

Chip Coons

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what if alert is showing but it can belong to other viewcontrollers and you don't know to each one? – Gargo Oct 24 '12 at 09:14
That sounds like a different question than the original poster asked. With the first part of the answer provide, it is implied that the owning viewcontroller is known, so your follow-up does not make sense. – Chip Coons Oct 24 '12 at 13:03
11

No need to have an ivar, just check `visible` property, as in the answer below. – sam-w Feb 18 '13 at 16:43
I checked isFirstResponder of the alert view for true, that also worked. – Saran Oct 07 '13 at 12:46
The visible property was not exposed at the time the original question was asked. Feel free to vote up the later answer if it is more correct now, but two years passed between the original question and the shift to properties (including visible). – Chip Coons Mar 21 '14 at 04:02
This code is not thread-safe. If multiple threads can show the alert, you should put this code in a @synchronized block, or you can have more than one alert. – andreacipriani Jul 16 '14 at 11:20
Make a category on UIAlertView (now UIAlertController) that returns ![self.view isHidden] as the value of alertShowing. If you give the alert's view a tag, that you have defined as an enum you can check that view by the tag's enum name. – Alex Zavatone Jul 31 '15 at 17:15

kennytm · Answer 3 · 2014-07-07T10:12:59.473

26

If you can control the other alert views, check the visible property for each of them.

In iOS 6 or before, when an alert appears, it will be moved to a _UIAlertOverlayWindow. Therefore, a pretty fragile method is to iterate through all windows and check if there's any UIAlertView subviews.

for (UIWindow* window in [UIApplication sharedApplication].windows) {
  NSArray* subviews = window.subviews;
  if ([subviews count] > 0)
    if ([[subviews objectAtIndex:0] isKindOfClass:[UIAlertView class]])
      return YES;
}
return NO;

This is undocumented as it depends on internal view hierarchy, although Apple cannot complain about this. A more reliable but even more undocumented method is to check if [_UIAlertManager visibleAlert] is nil.

These methods can't check if a UIAlertView from SpringBoard is shown.

edited Jul 07 '14 at 10:12

answered Mar 27 '10 at 14:49

kennytm

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one typo in your code "UIView* subviews = window.subviews; " it should be NSArray* subviews = window.subviews; by the way it helped me a lot thanks. – Rahul Vyas Dec 20 '11 at 12:42
@Deepesh, have you found solution ? – LiangWang Jul 06 '14 at 03:01
@Jacky, I am not found any right solution ... if you found any solution ... please paste your valuable answer ....Thanks – Deepesh Jul 07 '14 at 05:31

score 9 · Answer 4 · edited Apr 21 '15 at 16:08

9

- (BOOL)checkAlertExist {
    for (UIWindow* window in [UIApplication sharedApplication].windows) {
        NSArray* subviews = window.subviews;
        if ([subviews count] > 0) {
            for (id cc in subviews) {
                if ([cc isKindOfClass:[UIAlertView class]]) {
                    return YES;
                }
            }
        }
    }
    return NO;
}

edited Apr 21 '15 at 16:08

Gavin

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answered Mar 01 '13 at 06:28

Javen.Yang

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This will not work in iOS 7. The first subview could be a container. So you'd have to walk the entire possible tree. – Womble Jun 02 '14 at 02:00
@Womble, so have you found solution? – LiangWang Jul 06 '14 at 03:02

score 4 · Answer 5 · answered Oct 03 '13 at 09:24

Another option that works across the entire app and doesn't involve walking the view stack is to subclass UIAlertView to MyUIAlertView, add a static (class) variable BOOL alertIsShowing, and override the -(void)show selector.

In your overridden show selector, check the alertIsShowing variable. If it's YES then try again after a delay (use dispatch_after or set an NSTimer). If it's NO, go ahead and call [super show] and assign YES to alertIsShowing; when the alert view is hidden, set alertIsShowing back to NO (you'll need to be clever about handling the delegate).

Finally, go through and replace all UIAlertView instances with MyUIAlertView.

I like this answer (although I subclassed `UIAlertController` - if you're using both I would think you'd need to keep track of both). I did end up using a counter rather than a boolean. This way, if you attempt to show two alerts at the same time, you won't accidentally set the boolean to false if the appear/disappear methods get called out of sync from what you expect. — garie, May 02 '17 at 15:00

score 3 · Answer 6 · answered Jul 12 '16 at 12:35

Swift:

func showAlert(withTitle title: String, message: String, viewController: UIViewController) {
    if viewController.presentedViewController == nil { // Prevent multiple alerts at the same time
        let localizedTitle = NSLocalizedString(title, comment: "")
        let localizedMessage = NSLocalizedString(message, comment: "")
        let alert = UIAlertController(title: localizedTitle, message: localizedMessage, preferredStyle: .Alert)
        let action = UIAlertAction(title: "OK", style: .Default, handler: nil)
        alert.addAction(action)

        viewController.presentViewController(alert, animated: true, completion: nil)
    }
}

viewntroller.presentedViewController == nil did the trick. thanks — Kingalione, Sep 06 '16 at 09:14

score 3 · Answer 7 · answered Aug 25 '16 at 06:09

3

I think it will work:

-(BOOL) doesAlertViewExist {
    if ([[UIApplication sharedApplication].keyWindow isMemberOfClass:[UIWindow class]])
    {
        return NO;//AlertView does not exist on current window
    }
    return YES;//AlertView exist on current window
}

answered Aug 25 '16 at 06:09

Manab Kumar Mal

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less code `-(BOOL) doesAlertViewExist { return ![[UIApplication sharedApplication].keyWindow isMemberOfClass:[UIWindow class]]; }` – Popmedic Oct 10 '18 at 21:57

score 2 · Answer 8 · edited Apr 21 '15 at 16:07

// initialize default flag for alert... If alert is not open set isOpenAlert as NO
BOOL isAlertOpen;
isAlertOpen = NO;
if (isAlertOpen == NO) {
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Alert" message:@"Alert is Open" delegate:self cancelButtonTitle:@"Okay!!" otherButtonTitles: nil];
    [alert show];
    // Now set isAlertOpen to YES
    isAlertOpen = YES;
}
else
{
    //Do something
}

score 2 · Answer 9 · answered Mar 23 '16 at 16:14

+ (BOOL)checkAlertExist {

    for (UIWindow* window in [UIApplication sharedApplication].windows) {
        if ([window.rootViewController.presentedViewController isKindOfClass:[UIAlertController class]]) {
            return YES;
        }
    }
    return NO;
}

score 1 · Answer 10 · answered Sep 22 '15 at 19:55

Some notes on my quest to find the UIAlertView in the view hierarchy:

I tried to loop through all of the [UIApplication sharedApplication].windows view's recursively but couldn't find anything.

The windows property of UIApplication docs states the following:

This property contains the UIWindow objects currently associated with the app. This list does not include windows created and managed by the system, such as the window used to display the status bar.

So this made me realize that the UIWindow where UIAlertView could be located is not even presented to us.

HOWEVER, there is also a property on UIApplication called keyWindow. Upon looping through that, I found private classes that would compose an alert view:

On iOS 7: _UIModalItemHostingWindow, _UIModalItemAlertContentView, _UIBackdropEffectView etc.

On iOS 8: _UIAlertControllerActionView, _UIAlertControllerShadowedScrollView, _UIBackdropView etc.

I could not find the UIAlertView that I presented, but rather, a bunch of classes that compose it internally. So to answer the original question, you can probably use the keyWindow property and see if you notice these classes, but your app could get rejected for trying to check for private classes.

For folks using, the newer, UIAlertController available for iOS 8 could get the reference to it using: [UIApplication sharedApplication].keyWindow.rootViewController.presentedViewController.

Check if a UIAlertView is showing

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