iOS统一设置状态栏的样式，交给代理AppDelegate

1.info.plist文件增加一项

View controller-based status bar appearance 为 NO

2.AppDelegate.m文件

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // Override point for customization after application launch.
    
    //设置状态栏的样式
    application.statusBarStyle = UIStatusBarStyleLightContent;
    
    return YES;
}