iOS 导航栏遮挡视图处理

遮挡原因 ： iOS7之后导航栏新增了Translucent属性（透明度）导致View视图向上延伸

方法一

设置导航栏透明度：
swift : self.navigationController?.navigationBar.isTranslucent = false
OC : [self.navigationController.navigationBar setTranslucent:NO];

方法二

设置视图不延伸
swift : self.extendedLayoutIncludesOpaqueBars = false
self.edgesForExtendedLayout = UIRectEdge.init(rawValue: 0)
self.modalPresentationCapturesStatusBarAppearance = false;
OC : self.extendedLayoutIncludesOpaqueBars = NO;
self.edgesForExtendedLayout = UIRectEdgeTop;
self.modalPresentationCapturesStatusBarAppearance = NO

方法三

为导航栏设置背景图
swift:self.navigationController?.navigationBar.setBackgroundImage(UIImage.init(named: "back.png"), for: UIBarMetrics.default)
OC : [self.navigationController.navigationBar setBackgroundImage:[UIImage imageNamed:@"button_bg_88b048.png"] forBarMetrics:UIBarMetricsDefault]