iphone - 为什么在应用程序 :didFinishLaunchingWithOptions: causing an error? 中显示 UIAlertView

Question

在我的应用程序第一次运行时，我向用户显示一个警告 View 以选择 iCloud 或本地文档存储。显示警报 View 会导致以下错误:

Applications are expected to have a root view controller at the end of application launch wait_fences: failed to receive reply: 10004003

为什么会这样？如何在启动时显示警报 View 而不出现此错误？

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    // Check the user preferences for document storage options
    if (![UserPreferencesHelper userDocumentStoragePreferencesHaveBeenCreated])
    {
        // User preferences have not been set, prompt the user to choose either iCloud or Local data storage
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Use iCloud?" 
                                                        message:@"Would you like to store data in iCloud?" 
                                                       delegate:self 
                                              cancelButtonTitle:nil 
                                              otherButtonTitles:@"No", @"Yes", nil];
        [alert show];
    }
}

**更新**

我应该提一下，我使用的是带有 Storyboard的 iOS 5。 Root View Controller 设置在 Storyboard中。

Answer 1

尝试将 [alert show] 替换为:

[alert performSelector:@selector(show) withObject:nil afterDelay:0.0];

这会延迟单次通过运行循环的警报，大概允许您的应用程序的 Controller 和 Storyboard在出现警报之前完成它们的设置。