NavigationItem setTitle不适用于二级UIViewController

在我的应用程序中，我有一个UITabBarController与UINavigationControllers初始化如下

UINavigationController *newsNavigationController = [[UINavigationController alloc] initWithRootViewController: newsViewControler];

newsViewController是一个UIViewController . 当我按下标签栏中的按钮以使用newsViewController显示导航项时，导航栏中的 Headers 设置为ok . 在newsViewController中我有一个我在init之后调用的方法设置 . 在设置方法中，我将 Headers 设置为 [[self navigationItem] setTitle:[category_c title]];

问题出现了，在我的newsViewController中我有一个tableView，当我触摸一个单元格时，我想用所选新闻推送一个UIViewController，并在导航栏中显示 Headers .

在UIViewController中我有相同的设置方法，我在其中设置如上所述的 Headers . 问题是没有显示 . 导航项不为null，因为我可以调用 self.navigationItem.hidesBackButton = YES; 并且每次都隐藏后退按钮但 Headers 不显示 .

当触摸单元格时，我创建并推送新闻UIViewController

if(newsViewController == nil){
        newsViewController = [[NewsViewController alloc] init];
        [newsViewController setup];
    }
    [self.navigationController pushViewController: newsViewController animated:YES];

newsViewController中的setup方法如下所示：

- (void) setup {
    self.navigationItem.hidesBackButton = YES;
    [self.navigationItem setTitle:@"my view"];
}

在newsViewController我有viewDidLoad并试图在那里设置 Headers 但没有成功 .

• （void）viewDidLoad {self.navigationItem.title = @ "Test"; [super viewDidLoad]; }

如果 [self.navigationController pushViewController: newsViewController animated:YES]; 之后我写了包含UITableView的UIViewController获取 Headers myTitle而不是我触摸单元格时推送的newsViewController .

任何指针？我无法理解为什么 Headers 设置不正确 .

EDIT2: After reading a little more and going through my code with the debugger step by step and comparing the rootviewcontrollers with the childViewControllers i've observed that in the viewDidLoad method of the childViewController after setting self.title = @"title" the navigationItem is created so it's not the nil situation. In the debugger when i expand the _navigationItem variable the field _navigationBar is nil after leaving viewDidLoad, in the rootViewControllers the navigationBar is NOT NULL and the title is there. I read that if the navigationBar is null the title will not show up. In the image is what i've seen in the debuger. alt text http://img138.imageshack.us/img138/1513/picture2bq.png now i'm searching in this direction.

EDIT1: below is the code for the parentViewController, firstChildViewController and second ChildViewController. the parentViewController is viewed(the title is OK). I press a button on the navigationBar that calls bearbeitenAction -> the first child is pushed(title is not showed). On the navigation bar of the firstChildViewController i have a button that when is pressed pushes a new ViewController on the stack(secondChildViewController). The title of the second ChildViewController is not ok. When i press Back the title of the firstChildViewController is showed Ok.

parentViewController：

//MARK: -
    //MARK: Initialization methods
    - (void) setup {
        dataManipulator = [[DataManipulation alloc] init];
        dataManipulator.delegate = self;

        [self.tabBarItem initWithTitle:[NSString stringWithFormat:@"%@",[category_c title]] image:[UIImage newImageFromResource:[category_c icon]] tag:0];

        searchResults = nil;
        companyDetailsPushed = NO;
    }

    //MARK: -
    //MARK: ViewControllerMethods
    // Implement loadView to create a view hierarchy programmatically, without using a nib.
    - (void) loadView {
        NSLog(@"WatchlistViewController: loadView");

        UIView *mainView = [[[UIView alloc] initWithFrame:CGRectMake(0, 0, [[UIScreen mainScreen] applicationFrame].size.width, [[UIScreen mainScreen] applicationFrame].size.height)] autorelease];
        [mainView setBackgroundColor:[UIColor whiteColor]];
        mainView.autoresizingMask = UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth;
        mainView.contentMode = UIViewContentModeScaleToFill;
        [mainView setAutoresizesSubviews:YES];

            companiesTable = [[UITableView alloc] initWithFrame:CGRectMake(0, 44, [[UIScreen mainScreen] applicationFrame].size.width, 322)];
        companiesTable.delegate = self;
        companiesTable.dataSource = self;
        [mainView addSubview:companiesTable];
        [companiesTable release];

            self.view = mainView;
    }

    - (void)viewDidLoad {
        [super viewDidLoad];
        if(![[category_c subtitle] isEqualToString:@""]) {
            self.title = [category_c subtitle];
        }
        else {
            self.title = [category_c title];
        }
    }

    - (void) tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {

        if(companyDetailsViewController == nil) {
            companyDetailsViewController = [[CompanyDetailsScrollViewController alloc] init];
            [companyDetailsViewController setup];
        }

        [watchlistDoneBtn setHidden:TRUE];
        companyDetailsPushed = YES;

        if(viewMode == SearchViewMode)
            [companyDetailsViewController setCompany:[searchResults objectAtIndex:indexPath.row]];
        else if(viewMode == WatchlistViewMode)
            [companyDetailsViewController setCompany:[[[Financial_deAppDelegate sharedAppDelegate] watchlistCompanies] objectAtIndex:indexPath.row]];

        [[self navigationController] pushViewController:companyDetailsViewController animated:YES];
    }

- (void) bearbeitenAction:(UIButton *) sender {
    NSLog(@"Berbeiten btn was pressed");
    if(berbeitenViewController == nil){
        berbeitenViewController = [[BerbeitenViewController alloc] init];
        [berbeitenViewController setup];
    }
    [self.navigationController pushViewController:berbeitenViewController animated:YES];
}

firstChildViewController = berbeitenViewController中的代码：

- (void) setup {
    self.navigationItem.hidesBackButton = YES;
}

// Implement loadView to create a view hierarchy programmatically, without using a nib.
- (void)loadView {
    NSLog(@"BerbeitenViewController: loadView");

    UIView *mainView = [[[UIView alloc] initWithFrame:CGRectMake(0, 0, [[UIScreen mainScreen] applicationFrame].size.width, [[UIScreen mainScreen] applicationFrame].size.height)] autorelease];
    [mainView setBackgroundColor:[UIColor darkGrayColor]];
    mainView.autoresizingMask = UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth;
    mainView.contentMode = UIViewContentModeScaleToFill;
    [mainView setAutoresizesSubviews:YES];

    berbeitenBackBtn = [[UIButton alloc] initWithFrame:CGRectMake(5, 23, 69, 36)];
    [berbeitenBackBtn setBackgroundImage:[UIImage newImageFromResource:@"back_btn.png"] forState:UIControlStateNormal];
    [berbeitenBackBtn addTarget:self action:@selector(popViewController:) forControlEvents:UIControlEventTouchUpInside];
    [berbeitenBackBtn setEnabled:TRUE];
    [self.navigationController.view addSubview:berbeitenBackBtn];
    [berbeitenBackBtn release];

    berbeitenAddBtn = [[UIButton alloc] initWithFrame:CGRectMake(260, 23, 55, 36)];
    [berbeitenAddBtn setBackgroundImage:[UIImage newImageFromResource:@"bearbeiten_add_btn.png"] forState:UIControlStateNormal];
    [berbeitenAddBtn addTarget:self action:@selector(addCompany:) forControlEvents:UIControlEventTouchUpInside];
    [berbeitenAddBtn setEnabled:TRUE];
    [self.navigationController.view addSubview:berbeitenAddBtn];
    [berbeitenAddBtn release];

    companiesTable = [[UITableView alloc] initWithFrame:CGRectMake(0, 0, [[UIScreen mainScreen] applicationFrame].size.width, 366)];
    companiesTable.delegate = self;
    companiesTable.dataSource = self;
    [mainView addSubview:companiesTable];
    [companiesTable release];

    self.view = mainView;
}

- (void)viewDidLoad {
    NSLog(@"BerbeitenViewController viewDidLoad");
    [super viewDidLoad];
    self.title = @"Edit watchlist";
}

//MARK: Buttons actions

- (void) popViewController:(UIButton *) sender {
    NSLog(@"Pop BerbeitenViewController");
    [self.navigationController popViewControllerAnimated:YES];
}

- (void) addCompany:(UIButton *) sender {
    NSLog(@"Berbeiten addCompany btn pushed");
    if(searchViewController == nil){
        searchViewController = [[SearchViewController alloc] init];
        [searchViewController setup];
    }
    [self.navigationController pushViewController:searchViewController animated:YES];
}

secondChildViewController = searchViewController的代码

- (void) setup {
    self.navigationItem.hidesBackButton = YES;
}

// Implement loadView to create a view hierarchy programmatically, without using a nib.
- (void)loadView {
    NSLog(@"BerbeitenViewController: loadView");

    UIView *mainView = [[[UIView alloc] initWithFrame:CGRectMake(0, 0, [[UIScreen mainScreen] applicationFrame].size.width, [[UIScreen mainScreen] applicationFrame].size.height)] autorelease];
    [mainView setBackgroundColor:[UIColor darkGrayColor]];
    mainView.autoresizingMask = UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth;
    mainView.contentMode = UIViewContentModeScaleToFill;
    [mainView setAutoresizesSubviews:YES];

    searchViewBackBtn = [[UIButton alloc] initWithFrame:CGRectMake(5, 23, 69, 36)];
    [searchViewBackBtn setBackgroundImage:[UIImage newImageFromResource:@"back_btn.png"] forState:UIControlStateNormal];
    [searchViewBackBtn addTarget:self action:@selector(popViewController:) forControlEvents:UIControlEventTouchUpInside];
    [searchViewBackBtn setEnabled:TRUE];
    [self.navigationController.view addSubview:searchViewBackBtn];
    [searchViewBackBtn release];

    self.view = mainView;
}


// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad {
    [super viewDidLoad];
    self.title = @"Edit Watchlist";
}