使用std :: vector :: begin vs begin（vector）(Use std::vector::begin vs begin(vector))

 可能的根本原因 
 
 我有同样的问题，并且发现它正在发生，因为我没有在我的应用程序窗口中设置根视图控制器。 
 
 在其中实现了preferredStatusBarStyle的UIViewController在UITabBarController ，它控制了屏幕上的视图的外观。 
 
 当我将根视图控制器设置为指向此UITabBarController ，状态栏更改开始正常工作，正如预期的那样（并且preferredStatusBarStyle方法被调用）。 
 
(BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    ... // other view controller loading/setup code

    self.window.rootViewController = rootTabBarController;
    [self.window makeKeyAndVisible];
    return YES;
}
 
 替代方法（iOS 9中已弃用） 
 
 或者，您可以根据自己的背景颜色，在每个视图控制器中根据需要调用以下方法之一，而不必使用setNeedsStatusBarAppearanceUpdate ： 
 
[[UIApplication sharedApplication] setStatusBarStyle:UIStatusBarStyleLightContent];
 
 要么 
 
[[UIApplication sharedApplication] setStatusBarStyle:UIStatusBarStyleDefault];
 
 请注意，如果您使用此方法，您还需要在plist文件中将UIViewControllerBasedStatusBarAppearance设置为NO 。 

Possible root cause
 
I had the same problem, and figured out it was happening because I wasn't setting the root view controller in my application window. 
 
The UIViewController in which I had implemented the preferredStatusBarStyle was used in a UITabBarController, which controlled the appearance of the views on the screen.
 
When I set the root view controller to point to this UITabBarController, the status bar changes started to work correctly, as expected (and the preferredStatusBarStyle method was getting called).
 
(BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    ... // other view controller loading/setup code

    self.window.rootViewController = rootTabBarController;
    [self.window makeKeyAndVisible];
    return YES;
}
 
Alternative method (Deprecated in iOS 9)
 
Alternatively, you can call one of the following methods, as appropriate, in each of your view controllers, depending on its background color, instead of having to use setNeedsStatusBarAppearanceUpdate:
 
[[UIApplication sharedApplication] setStatusBarStyle:UIStatusBarStyleLightContent];
 
or
 
[[UIApplication sharedApplication] setStatusBarStyle:UIStatusBarStyleDefault];
 
Note that you'll also need to set UIViewControllerBasedStatusBarAppearance to NO in the plist file if you use this method.