Question

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {    

    // Override point for customization after application launch.

    // Add the view controller's view to the window and display.

    [window addSubview:viewController.view];
    MainPageDialog *overviewViewController = [[MainPageDialog alloc] initWithNibName:@"MainPage" bundle:nil];
    UINavigationController *nav_obj = [[UINavigationController alloc] initWithRootViewController:overviewViewController ];

    [self.viewController presentModalViewController:nav_obj  animated:YES];
    [overviewViewController release];
    [self.window makeKeyAndVisible];

    return YES;
}

This code shows the blue bar of navigation controller, but no buttons on it.It seems like to be that the UINavigationController allocated as empty.
Who knows what problems is?

UPD:Archive http://www.mediafire.com/?lbjjvl6fcue2q18
Please help me, I’m new in objective-c

Answer 1

The correct way to use a UINavigationController is to push view controllers on to it. That way they will be stacked and the navigation bar will be populated with a back button when it is case (i.e., when you can actually go back to a previous controller). You control the label that appears in the “back” button by defining the title of the controllers you push.

The technique shown in another answer (setting explicitly the button) is useful with defining the right button, if you ever need one.

You could try with this code:

 - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {    

    MainPageDialog *overviewViewController = [[MainPageDialog alloc] initWithNibName:@"MainPage" bundle:nil];
    UINavigationController* navigation = [[UINavigationController alloc] init];
    [navigation pushViewController:overviewViewController animated:NO];
    [overviewViewController release];

    [window addSubview:[navigation view]];
    [self.window makeKeyAndVisible];

    return YES;
}

Instead of doing:

    UINavigationController* navigation = [[UINavigationController alloc] init];
    [navigation pushViewController:overviewViewController animated:NO];

you could also use initWithRootController, but to display the general case of how you push a view controller I preferred this one.

Notice that since you are pushing just a root controller, you should see no back button at the moment, but if you push a second view controller, then it will appear.

EDIT: I gave a look at your project. Summary of what you should try and do:

1. objects you need in your NIB: File’s Owner (UIApplication), First Responder, FBFun App Delegate (iVkAppDelegate), Window (UIWindow); remove the rest;

2. File’s owner delegate outlet is FBFun App Delegate;

3. FBFun App Delegate window outlet is Window.

With this simple setup (more or less what you have), use this code :

 - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {    

     UINavigationController* navigation = [[UINavigationController alloc] init];

     //--    MainPageDialog *overviewViewController = [[MainPageDialog alloc] initWithNibName:@"MainPage" bundle:nil];
     iVkViewController *overviewViewController = [[iVkViewController alloc] init];
 overviewViewController.title = @"First";
     [navigation pushViewController:overviewViewController animated:NO];

     iVkViewController *overviewViewController2 = [[iVkViewController alloc] init];
 overviewViewController2.title = @"Second";
     [navigation pushViewController:overviewViewController2 animated:NO];

    [overviewViewController release];
    [window addSubview:[navigation view]];
    [self.window makeKeyAndVisible];

    return YES;
}

In the code above, as you notice, I instantiated twice your iVkViewController just to have a second controller to push onto the navigator.

Please, delete your existing app from the simulator, and the run this in order to see that the navigation bar is correctly created and you can go back from the second controller to the first one.

I removed usage of MainPageDialog, because the MainPage nib has many problems.

But I hope this skeleton is sufficient for you to go forward with your development.