默认状态栏为黑色，对于某些App不是很美观，变成白色很简单，只需要两个步骤。
1.在Info.plist中添加新项目，View controller-based status bar appearance，Boolean值为No.
2.在AppDelegate的- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions方法中添加
[[UIApplication sharedApplication] setStatusBarStyle:UIStatusBarStyleLightContent animated:NO];
2017.04.11更新
Swift版本为
UIApplication.shared.statusBarStyle = UIStatusBarStyle(rawValue: 1)!
或者
UIApplication.shared.statusBarStyle = UIStatusBarStyle.init(rawValue: 1)!
)
