以编程方式向UINavigationController添加按钮

Question

我认为这应该是一个简单的,但我只是在挠头.我有一个应用程序,在故事板中设置了多个ViewControllers.我希望每个视图的每个视图顶部都有相同的导航栏,但是这个导航控制器在所有视图上都有相同的按钮.导航控制器在AppDelegate中设置,按钮添加到每个ViewController的ViewDidLoad中(根据我在这里收到的另一个问题的答案),但此时,按钮(和标题)没有显示.

设置UINavigationController的位置 - AppDelegate.m:

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

    UIStoryboard *mainStoryboard = [UIStoryboard storyboardWithName:@"Main" bundle: nil];
    MainViewController* mainVC = [mainStoryboard instantiateInitialViewController];
    UINavigationController *navVC = [[UINavigationController alloc] initWithRootViewController:mainVC];

    [self.window setRootViewController:navVC];

    [_window makeKeyAndVisible];

    return YES;
}

其中一个观点:

- (void)viewDidLoad
{

    [self setTitle:@"Congress app"];  // < This does not set the title of the NavController

    UIBarButtonItem *showSettingsButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemAction target:self action:@selector(showSettings:)];
    UIBarButtonItem *showMenuButton = [[UIBarButtonItem alloc] initWithImage:[UIImage imageNamed:@"menuButton.png"] style:UIBarButtonItemStylePlain target:self action:@selector(revealMenu:)];

    //self.navigationItem.leftBarButtonItem = showMenuButton;
    //self.navigationItem.rightBarButtonItem = showSettingsButton;
    self.navigationController.navigationItem.leftBarButtonItem = showMenuButton;
    self.navigationController.navigationItem.rightBarButtonItem = showSettingsButton;

    UINavigationController *currentNav;
    UIViewController *VCname;   
    NSLog(@"First left button in navigation controller - %@", [self.navigationController.navigationItem.leftBarButtonItems objectAtIndex:0]);
    NSLog(@"First right button in navigation controller - %@", [self.navigationController.navigationItem.rightBarButtonItems objectAtIndex:0]);
    [super viewDidLoad];  
}

我有几个NSLog显示导航控制器中有什么(如果有的话),它显示:以及哪些按钮被添加但未显示？

编辑:

我记得在上面的代码中有一个在VC之前触发的ViewController(InitViewController.m).NavigationController在这里分配:

- (void)viewDidLoad
{
[super viewDidLoad];

self.topViewController = [self.storyboard instantiateViewControllerWithIdentifier:@"MainVC"];
}

这很可能是问题的原因.

编辑2:

感谢Saurav Mac,我已经跟踪了问题,试图在"错误"的视图控制器上添加按钮.我在AppDelegate.m中安装了导航控制器,第一个视图控制器是InitViewController,然后调用MainViewController作为'顶视图控制器'.不敢相信我错过了,谢谢你的帮助.

Answer 1

您可以在公共类(即NSObject的子类)中创建此按钮,然后可以在要添加按钮的每个类中调用此方法,也可以将此代码添加到每个类的ViewDidLoad方法中 -

self.navigationItem.leftBarButtonItem=[[UIBarButtonItem alloc]init];

UIImage *img1=[UIImage imageNamed:@"image.png"];
CGRect frameimg1 = CGRectMake(0, 0, img1.size.width, img1.size.height);
UIButton *signOut=[[UIButton alloc]initWithFrame:frameimg1];
[signOut setBackgroundImage:img1 forState:UIControlStateNormal];
[signOut addTarget:self action:@selector(BackButtonPressed)
  forControlEvents:UIControlEventTouchUpInside];
[signOut setShowsTouchWhenHighlighted:YES];

UIBarButtonItem *barButton=[[UIBarButtonItem alloc]initWithCustomView:signOut];
self.navigationItem.leftBarButtonItem=barButton;