iPhone SDK: 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?

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

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

---

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) {
  UIView* 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.