UINavigationController不出現？

Question

我在那裏當你在Category挖掘，下面的代碼被執行

- (void)categoryTapped { 
    CategoryGroupViewController *categoryGroupViewController = [[CategoryGroupViewController alloc] initWithNibName:@"CategoryGroupViewController" bundle:nil]; 
    [self presentViewController:categoryGroupViewController animated:YES completion:nil]; 
} 

CategoryGroupViewController.h看起來像

@interface CategoryGroupViewController : UIViewController<UITableViewDataSource, UITableViewDelegate> 
@property (nonatomic, strong) UINavigationController *navigationController; 
@property (strong, nonatomic) IBOutlet UITableView *tableView; 
@end 

CategoryGroupViewController.m看起來像

#import "CategoryGroupViewController.h" 
#import "Helper.h" 

static NSString *CellIdentifier = @"Cell"; 

@interface CategoryGroupViewController() 
@property(nonatomic, strong) NSArray *categories; 
@end 

@implementation CategoryGroupViewController 

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil { 
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]; 
    if (self) { 
     // (todo) should come from API 
     self.categories = @[@"Food & Drink", @"Utilities"]; 
    } 
    [self.tableView registerClass:[UITableViewCell class] forCellReuseIdentifier:CellIdentifier]; 
    return self; 
} 

- (void)viewDidLoad { 
    [super viewDidLoad]; 
    // Do any additional setup after loading the view from its nib. 
    NSLog(@"categoryGroup View loaded"); 
    self.navigationController = [[UINavigationController alloc] initWithRootViewController:self]; 
    self.navigationController.title = @"Pick Category"; 
} 
... 
} 

當我運行我的應用程序Add View ，我在日誌中看到以下內容

2014-11-20 21:29:53.589 myapp-ios[30332:70b] categoryGroup View loaded 

但在模擬器，我看到

爲什麼我看不到NavigationController？

Answer 1

當您在展示您的CategoryGroupViewController時，默認情況下它不會顯示導航欄。

你必須設置你的CategoryGroupViewController爲rootViewController爲UINavigationController和，而不是呈現CategoryGroupViewController目前新創建UINavigationController。

- (void)categoryTapped{ 
    CategoryGroupViewController *categoryGroupVC = [[CategoryGroupViewController alloc] initWithNibName:@"CategoryGroupViewController" bundle:nil];  
    UINavigationController *navController = [[UINavigationController alloc]initWithRootViewController: categoryGroupVC]; 
    [self presentViewController:categoryGroupViewController animated:YES completion:nil]; 
} 

Answer 2

您需要實例化一個RootViewController的查看以前那樣負載 [ALINK] https://developer.apple.com/library/ios/featuredarticles/ViewControllerPGforiPhoneOS/ViewLoadingandUnloading/ViewLoadingandUnloading.html

Answer 3

正如我上面提到如果u想要navigaioncontrollerü可以設置CategoryGroupViewController作爲用於導航控制器根視圖並將其顯示例如

- (void)categoryTapped 
{ 
    CategoryGroupViewController *categoryGroupViewController = [[CategoryGroupViewController alloc] initWithNibName:@"CategoryGroupViewController" bundle:nil]; 
    //add this   
    UINavigationController *navController = [[UINavigationController alloc]initWithRootViewController: categoryGroupViewController]; 
    //present the navigation controller which contains root view controller categoryGroupViewController 
    [self presentViewController:navController animated:YES completion:nil]; 
} 

Answer 4

的UIViewController已經作爲navigationController property，所以這是多餘的：

// Remove this property from CategoryGroupViewController 
@property (nonatomic, strong) UINavigationController *navigationController; 

構建在您嘗試的方式，用戶界面也是不正確的，並會導致CategoryGroupViewController和UINavigationController的之間的循環引用。首先，你需要修改-viewDidLoad方法，像這樣：

- (void)viewDidLoad { 
    [super viewDidLoad]; 
    // Do any additional setup after loading the view from its nib. 
    NSLog(@"categoryGroup View loaded"); 

    // UINavigationController will use this automatically. 
    self.title = @"Pick Category";  
} 

那麼你應該改變你去你的原始方法preseting視圖控制器的方式：

- (void)categoryTapped { 
    CategoryGroupViewController *categoryGroupViewController = [[CategoryGroupViewController alloc] initWithNibName:@"CategoryGroupViewController" bundle:nil]; 
    UINavigationController *navController = [[UINavigationController alloc] initWithRootViewController:categoryGroupViewController]; 
    [self presentViewController:navController animated:YES completion:nil]; 
} 

最後，introduction in the UINavigationController documentation有很大的應該如何使用該類的解釋。花幾分鐘時間閱讀它將在未來幫助你。