1，在plist文件里设置
2代码里设置
[applicationsetStatusBarStyle:UIStatusBarStyleLightContent];
self.window.clipsToBounds=YES;
plist里View controller-based status bar appearance设置为NO；
在didFinishLaunchingWithOptions方法里面设置
[application setStatusBarStyle:UIStatusBarStyleLightContent];
self.window.clipsToBounds =YES;
self.window.frame = CGRectMake(0,20,_window.frame.size.width,_window.frame.size.height - 20);//空出20px，将状态栏给单独显示出来
