单独的viecontroller设置状态栏

1.修改Info.plist文件  添加一个View controller-based status bar appearance 并设置为YES（这样viewcontroller设置状态栏的优先级高于［UIApplication shareApplication]设置状态栏的优先级）

2.在viewWillAppear中添加（网上看到是说在viewDidLoad中添加，试过之后没有效果）

UIView *statusBarView=[[UIView alloc] initWithFrame:CGRectMake(0, 0, CGRectGetWidth(self.view.frame), 20)];
[self.view addSubview:statusBarView];
[self setNeedsStatusBarAppearanceUpdate];

3.添加方法
- (UIStatusBarStyle)preferredStatusBarStyle
{
    return UIStatusBarStyleLightContent;
}
- (BOOL)prefersStatusBarHidden
{
    return NO;
}