我在控制台得到以下错误:

应用程序在启动结束时应该有一个根视图控制器

下面是我的应用程序:didFinishLaunchWithOptions方法:

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

    // Set Background Color/Pattern
    self.window.backgroundColor = [UIColor blackColor];
    self.tabBarController.tabBar.backgroundColor = [UIColor clearColor];
    //self.window.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"testbg.png"]];

    // Set StatusBar Color
    [[UIApplication sharedApplication] setStatusBarStyle:UIStatusBarStyleBlackTranslucent];

    // Add the tab bar controller's current view as a subview of the window
    self.window.rootViewController = self.tabBarController;
    [self.window makeKeyAndVisible];
    return YES;
}

在Interface Builder中,UITabBarController的委托被连接到App委托。

有人知道怎么解决这个问题吗?


当前回答

我在使用自定义ServiceLocator使用CoreData时得到了这样的错误

let context: NSManagedObjectContext = try self.dependencies.resolve()

//solution
let context: NSManagedObjectContext? = try? self.dependencies.resolve()

其他回答

在升级到Xcode 4.3后,我开始遇到同样的问题,而且只有在从头开始一个项目时(即创建一个空项目,然后创建一个UIViewController,然后创建一个单独的nib文件)。

在把我习惯的所有行,并确保我有正确的连接后,我一直得到这个错误,我试图通过视图控制器加载的nib文件(它被设置为rootController)从未在模拟器中显示。

我通过Xcode创建了一个视图模板,并将其与我的代码进行了比较,最终发现了问题!

Xcode 4.3 appears to add by default the method -(void)loadView; to the view controller implementation section. After carefully reading the comments inside it, it became clear what the problem was. The comment indicated to override loadView method if creating a view programmatically (and I'm paraphrasing), otherwise NOT to override loadView if using a nib. There was nothing else inside this method, so in affect I was overriding the method (and doing nothing) WHILE using a nib file, which gave the error.

解决方案是从实现部分完全删除loadView方法,或者通过添加[super loadView]来调用父方法。

如果使用NIB文件,则最好删除它,因为添加任何其他代码都会覆盖它。

如果你使用MTStatusBarOverlay,你会得到这个错误。

MTStatusBarOverlay创建了一个额外的窗口([[UIApplication sharedApplication] windows),它没有根控制器。

这似乎没有引起问题。

我也有这个错误,但不像之前列出的任何答案,我的是因为我在我新生成的控制器(xcode 4.2, ios5)中取消了“loadView”方法的注释。

 //Implement loadView to create a view hierarchy programmatically, without using a nib.
- (void)loadView  
{
}

它甚至告诉我,该方法是为创建视图编程,但我错过了它,因为它看起来如此类似于其他方法,如viewDidLoad,我通常使用我没有抓住它。

要解决这个问题,只需删除该方法,如果你不是通过编程方式创建视图层次结构,也就是使用nib或storyboard。

在使用XCode 4.6.3和iOS 6.1将我的UI替换为Storyboard后收到相同的错误

通过清除AppDelegate中的didFinishLaucnhingWithOptions中的所有代码来解决这个问题

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    return YES;
}

OrdoDei给出了一个正确而有价值的答案。我添加这个答案只是为了给出一个didFinishLaunchingWithOptions方法的例子,该方法使用了他的答案以及其他关于导航控制器的评论。

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

    // Override point for customization after application launch.

    // Instantiate the main menu view controller (UITableView with menu items).
    // Pass that view controller to the nav controller as the root of the nav stack.
    // This nav stack drives our *entire* app.
    UIViewController *viewController = [[XMMainMenuTableViewController alloc] init];
    self.navigationController = [[UINavigationController alloc] initWithRootViewController:viewController];

    // Instantiate the app's window. Then get the nav controller's view into that window, and onto the screen.
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    // [self.window addSubview:self.navigationController.view];
    // The disabled line above was replaced by line below. Fixed Apple's complaint in log: Application windows are expected to have a root view controller at the end of application launch
    [self.window setRootViewController:self.navigationController];
    self.window.backgroundColor = [UIColor whiteColor];
    [self.window makeKeyAndVisible];
    return YES;
}