Question

In my UIViewController I have a UINavigationController with a default back button. When the user clicks the back button, a warning message should appear: “Do you really want to go back?”. I know, that it is not possible to trap the back button event. It’s only possible the use viewWillDisappear and set a flag:

- (void)viewWillDisappear:(BOOL)animated {
    if (backBtnPressed) {
        UIAlertView *alert = [[[UIAlertView alloc] initWithTitle:@"Question" message:@"Do you really want to go back?" delegate:self cancelButtonTitle:@"No" otherButtonTitles: @"Yes", nil] autorelease];
        [alert show];   
    }
}

- (void)alertView:(UIAlertView *)alertView didDismissWithButtonIndex:(NSInteger)buttonIndex {
    if (buttonIndex == 0) {
        // don't go back!
        // cancel the back button event
    }
    else if (buttonIndex == 1) {
        // go back
    }
}

But with this code I have no chance! I can’t stop the back button event, isn’t it?

Do I have to write my own back button and set it as leftBarButtonItem? Or is there anybody with a great idea? 🙂

Thanks for your help!

Answer 1

viewWillDisappear is a delegate method for the event that the view is going to disappear – and there’s nothing the developer can do about that! If you could, it would be a viewShouldDisappear delegate method.

So I guess the only way is as you suggest, to use a custom leftBarButtonItem.