有关在应用程序启动结束时拥有根视图控制器的错误消息

Question

Stack Overlow上有一些关于此错误的问题，但没有一个解决方案对我有用。有人能够浏览我的代码，看看为什么我收到以下错误？

  

应用程序在应用程序启动结束时应该有一个根视图控制器

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;