编译Xcode项目应用程序窗口应具有根视图控制器

如何修复此错误？iphone模拟器可以工作，但当我使用ipad时，我会在控制台中看到这个。。2013-05-25 20:59:17.556您的RSS[2717:c07]应用程序窗口预计在应用程序启动结束时会有一个根视图控制器

    //
//  AppDelegate.m
//  YourRSS
//
//  Created by Mohammad Komeili on 5/17/13.
//  Copyright (c) 2013 MOMEKS. All rights reserved.
//

#import "AppDelegate.h"
#import "ViewController.h"
#import "ViewController_iPad2.h"


@implementation AppDelegate

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

    if ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPhone) {
        self.viewController = [[ViewController alloc] initWithNibName:@"ViewController_iPhone" bundle:nil];
        self.navigationController = [[UINavigationController alloc] initWithRootViewController:self.viewController];
    }
  /*  }else{

        self.viewController = [[ViewController alloc] initWithNibName:@"ViewController_iPad2" bundle:nil];
        self.navigationController = [[UINavigationController alloc] initWithRootViewController:self.viewController];
    }
    */

    self.navigationController.navigationBarHidden = YES;
    self.window.rootViewController = self.navigationController;
    [self.window makeKeyAndVisible];
    return YES;
}

- (void)applicationWillResignActive:(UIApplication *)application
{
    // Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
    // Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game.
}

- (void)applicationDidEnterBackground:(UIApplication *)application
{
    // Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later. 
    // If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
}

- (void)applicationWillEnterForeground:(UIApplication *)application
{
    // Called as part of the transition from the background to the inactive state; here you can undo many of the changes made on entering the background.
}

- (void)applicationDidBecomeActive:(UIApplication *)application
{
    // Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
}

- (void)applicationWillTerminate:(UIApplication *)application
{
    // Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.
}

@end

---

注释掉的代码部分是如果您不在iPhone上会执行的代码（请参阅：

UIUserInterfaceIdiomPhone

）。由于您在iPad上时跳过了导航控制器的创建过程，因此导航控制器保持为

nil

…这会给您带来明显的错误。

可能重复：请帮助，这是不同的代码。。。我是新的编码，我需要知道如何修复。请注意，我有以下xib。我认为您正在用较新的iOS编译一个较旧的项目。尝试创建一个新项目，复制类，在xib中建立必要的连接，然后再次编译。警告将消失。检查您的导航控制器是否正常。当我更改时，我现在遇到此问题。我不知道您所说的“此”问题是什么意思，我也不知道您更改了什么。