IOS7、IOS6 UINavigationController遮挡

在UIVIewController中加入：
        if ([[[UIDevice currentDevice] systemVersion] floatValue] >= 7.0) {
            self.edgesForExtendedLayout = UIRectEdgeNone;
            
            self.extendedLayoutIncludesOpaqueBars = NO;
            self.modalPresentationCapturesStatusBarAppearance = NO;
        }