ios - 关于在应用程序启动结束时有 Root View Controller 的错误消息

Question

Stack Overlow 上有一些关于此错误的问题，但似乎没有一个解决方案对我有用。有人能看一眼我的代码，看看我为什么会收到以下错误吗？

Applications are expected to have a root view controller at the end of application launch

AppDelegate.m:

#import "AppDelegate.h"
#import "ViewController.h" //import header file

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    // Override point for customization after application launch.
    UIStoryboard*  sb = [UIStoryboard storyboardWithName:@"Main" bundle:nil];
    UIViewController* viewController = [sb instantiateViewControllerWithIdentifier:@"viewController"];
    self.window.rootViewController = self.viewController;
    [self.window makeKeyAndVisible];
    return YES;
}

@end

Answer 1

您将 rootViewController 设置为 self.viewController 但您从未设置 self.viewController。

试试这个:

self.viewController = [sb instantiateViewControllerWithIdentifier:@"viewController"];
self.window.rootViewController = self.viewController;