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.

Answer 1

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.

Answer 2

- (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;
}

Answer 3

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.

Answer 4

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
}

Answer 5

// 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
}

Answer 6

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.