I want to display, above any other views, even the navigation bar, a kind of \"pop-up\" view that looks like this:
I recommend you to create a new UIWindow:
UIWindow *window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
window.rootViewController = viewController;
window.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
window.opaque = NO;
window.windowLevel = UIWindowLevelCFShareCircle;
window.backgroundColor = [UIColor clearColor];
[window makeKeyAndVisible];
Then you can manage your view in an other UIViewController. To remove the windows:
[window removeFromSuperview];
window = nil;
hope that will help!