Managing navigation controllers / view controllers - objective-c

Question

Not sure how to title this question, but i'v got such a problem: Up until now i my app runs mainly in one navigationcontroller with table views. But now i'm trying to integrate dropdown settings menu, and can't get it properly done.
The way i'v done now and it works
The changeController is called from one button. ChangeController is in appdelegate.
- (void) ChangeController
{
self.window.backgroundColor = [UIColor blackColor];
DropDownExample *e = [[DropDownExample alloc] initWithStyle:UITableViewStyleGrouped];
self.navigationController = [[UINavigationController alloc] initWithRootViewController:e];
[e release];
[self.window addSubview:self.navigationController.view];
self.window.backgroundColor = [UIColor blackColor];
[self.window makeKeyAndVisible];
}
But this approach has consequances - there is no transition if button is pressed, the settings menu appears instantly, you cannot go back via navigation bar above (nothing there).
So how to do this properly?? I'm new to ios, so just tell me the whole idea how to do this.
Didfinishlaunchingwithoptions method from appdelegate
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease
];
// Override point for customization after application launch.
self.window.backgroundColor = [UIColor whiteColor];
TableViewController *tableVC = [[TableViewController alloc] initWithNibName:#"TableView" bundle:nil andType:CONTROLLER_TYPE_FIRST];
UINavigationController *navC = [[UINavigationController alloc] initWithRootViewController:tableVC];
self.navigationController = navC;
[tableVC release];
[navC release];
self.window.rootViewController = _navigationController;
[self.window makeKeyAndVisible];
return YES;
}

Answer 1

Ok, here's the answer. Write the method changeController in the same class where the Button exists which calls changeController
In the method, write this.
- (void) ChangeController
{
DropDownExample *e = [[DropDownExample alloc] initWithStyle:UITableViewStyleGrouped];
[self.navigationController pushViewController:e animated:YES];
[e release];
}
What you want is to insert new UIViewController on the top of the present Stack. If you would be having a navigation Bar at the top by default then there would be a back Btn by default, which would pop up that controller.