Enabling the photo library button on the UIImagePickerController

- (void) navigationController: (UINavigationController *) navigationController  willShowViewController: (UIViewController *) viewController animated: (BOOL) animated {
    if (imagePickerController.sourceType == UIImagePickerControllerSourceTypePhotoLibrary) {
        UIBarButtonItem* button = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemCamera target:self action:@selector(showCamera:)];
        viewController.navigationItem.rightBarButtonItems = [NSArray arrayWithObject:button];
    } else {
        UIBarButtonItem* button = [[UIBarButtonItem alloc] initWithTitle:@"Library" style:UIBarButtonItemStylePlain target:self action:@selector(showLibrary:)];
        viewController.navigationItem.leftBarButtonItems = [NSArray arrayWithObject:button];
        viewController.navigationItem.title = @"Take Photo";
        viewController.navigationController.navigationBarHidden = NO; // important
    }
}

- (void) showCamera: (id) sender {
    imagePickerController.sourceType = UIImagePickerControllerSourceTypeCamera;
}

- (void) showLibrary: (id) sender {
    imagePickerController.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
}