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

Question

我的应用程序今天早些时候启动正常，但现在我收到此错误

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

我看过其他线程说要更改我的代码，但我从未更改过任何代码来达到这一点。

委托(delegate).h

@interface halo4AppDelegate : NSObject <UIApplicationDelegate, UITabBarControllerDelegate>{
    UIWindow *window;
    UITabBarController *tabBarController;
}

@property (nonatomic, retain) IBOutlet UIWindow *window;
@property (nonatomic, retain) IBOutlet UITabBarController *tabBarController;

@end

委托(delegate).m

@implementation halo4AppDelegate

@synthesize window;
@synthesize tabBarController;


#pragma mark -
#pragma mark Application lifecycle

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions 
{   
    sleep(3);
    self.window.rootViewController = self.tabBarController;
    [self.window makeKeyAndVisible];
    return YES;
}


#pragma mark -
#pragma mark Memory management

- (void)dealloc {
    [tabBarController release];
    [window release];
    [super dealloc];
}

@end

我的 FirstViewController 的 xib 是标题 FirstView.xib , ext

Answer 1

这不是错误，更像是警告。

在您的应用程序委托(delegate)中有一个名为 application:didFinishLaunchingWithOptions: 的方法，在此方法中您必须在该方法结束之前添加此行self.window.rootViewController = [Some UIViewController ]

再次强调，这不是错误，如果您有其他方法来创建此 rootViewController，则可以忽略 rootViewController。

编辑

您的方法应该如下所示:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    // Override point for customization after application launch.
  UIViewController *viewController1 = [[FirstViewController alloc] initWithNibName:@"FirstViewController" bundle:nil];
  UIViewController *viewController2 = [[SecondViewController alloc] initWithNibName:@"SecondViewController" bundle:nil];
  self.tabBarController = [[UITabBarController alloc] init];
  self.tabBarController.viewControllers = @[viewController1, viewController2];
  self.window.rootViewController = self.tabBarController;
    [self.window makeKeyAndVisible];
    return YES;
}