iOS 7及以上，随时改变UIStatusBar颜色

UIStatusBarStyleDefault：字体为黑色（时间、运营商、WiFi等标志的显示颜色）

UIStatusBarStyleLightContent:字体为白色

1.plist中设置View controller-based status bar appearance为NO

2.- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions中设置

[[UIApplication sharedApplication] setStatusBarStyle:UIStatusBarStyleDefault];//当前黑色，如果要白色可以改成UIStatusBarStyleLightContent



3.如果有单独一个ViewController为白色，可以这样设置

- (void)viewWillAppear:(BOOL)animated

{

[super viewWillAppear:animated];

[[UIApplication sharedApplication] setStatusBarStyle:UIStatusBarStyleLightContent];//白色

}

-(void)viewWillDisappear:(BOOL)animated

{

[super viewWillDisappear:animated];

[UIApplication sharedApplication].statusBarStyle = UIStatusBarStyleDefault;//退出当前ViewController后变回黑色

}