Modal方式显示UIView

+ (void)showModal:(UINavigationController*)parentController
{
    static LoginController* sharedController;
    static UINavigationController *navigationController;
    if(!sharedController)
    {
        sharedController = [[LoginController alloc] initWithNibName:@"Login" bundle:nil modal:YES];
        navigationController = [[UINavigationController alloc] initWithRootViewController:sharedController];
    }
   
    [parentController presentModalViewController:navigationController animated:YES];
}