Question

I know this is extremely silly.

I have a view controller that scans a QR code. I create it in the AppDelegate (didFinishLaunchingWithOptions), and I also set my AppDelegate as a delegate for the the view controller which will call a method when he finishes scanning the code. In that method, that I have implemented in the AppDelegate I want to present a UINavigationController. The problem is that it is not presenting my navigation controller. This is my code:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    // Override point for customization after application launch.
    reader=[ZBarReaderViewController new];
    reader.readerDelegate=self;
    reader.supportedOrientationsMask=ZBarOrientationMaskAll;
    ZBarImageScanner *scanner=reader.scanner;
    [scanner setSymbology:ZBAR_I25 config:ZBAR_CFG_ENABLE to:0]; 


   [self.window addSubview:reader.view];
   [self.window makeKeyAndVisible];
   return YES;
}

-(void) imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
    RootViewController *rootViewController=[[RootViewController alloc] init ];  //create root view controller

    UINavigationController *navigationController=[[UINavigationController alloc] initWithRootViewController:rootViewController];  // create and init navigation controller with viewController
    [navigationController setValue:[[GradientBar alloc] init] forKey:@"navigationBar"];

    rootViewController.title=@"mTLU";
    [reader presentModalViewController:navigationController animated:NO];

}

Answer 1

Seems like you forgot to set self.window.rootViewController in didFinishLaunchingWithOptions:

Try:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
   self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
   // Override point for customization after application launch.
   self.reader=[ZBarReaderViewController new];
   self.reader.readerDelegate=self;
   self.reader.supportedOrientationsMask=ZBarOrientationMaskAll;
   ZBarImageScanner *scanner=reader.scanner;
   [scanner setSymbology:ZBAR_I25 config:ZBAR_CFG_ENABLE to:0]; 

   self.window.rootViewController = self.reader;

   [self.window addSubview:reader.view];
   [self.window makeKeyAndVisible];
   return YES;
}

This code assumes reader is property of AppDelegate. If it’s only iVar you should ommit self. (or consider making it a property).