//设置导航返回按钮 不让back 出现app
let image = UIImage(named: "nav_back")?.withRenderingMode(UIImageRenderingMode.alwaysOriginal)it
(UINavigationBar.appearance()).backIndicatorImage = imageio
(UINavigationBar.appearance()).backIndicatorTransitionMaskImage = imageim
(UIBarButtonItem.appearance()).setBackButtonTitlePositionAdjustment(UIOffset.init(horizontal: 0, vertical: -60), for: .default)di