ios默认viewController的View会延伸到最顶端，即使上面有导航条、状态栏，可以设置edgesForExtendedLayout属性
f([[[UIDevice currentDevice] systemVersion] floatValue] >= 7.0){
self.edgesForExtendedLayout = UIRectEdgeNone;
self.automaticallyAdjustsScrollViewInsets = NO;
}
原文：http://my.oschina.net/u/1781028/blog/411664