http://www.jianshu.com/p/5aa05983b445
http://www.cnblogs.com/alby/archive/2015/10/07/4859537.html
在plist中添加属性
View controller-based status bar appearance 置为NO
然后可以根据代码设置
[[UIApplication sharedApplication] setStatusBarStyle:UIStatusBarStyleLightContent animated:YES];
[[UIApplication sharedApplication] setStatusBarStyle:UIStatusBarStyleDefault animated:YES];