1、Appdelegate

    func application(_ application: UIApplication, supportedInterfaceOrientationsFor window: UIWindow?) -> UIInterfaceOrientationMask {

        ifself.allowRotation=="1"{

            return UIInterfaceOrientationMask.landscape

        }else{

            return UIInterfaceOrientationMask.portrait

        }

    }

2、vc 需要横屏的页面

        let appdelegate: AppDelegate = UIApplication.shared.delegate as! AppDelegate

        appdelegate.allowRotation="1"

返回的时候

        let appdelegate: AppDelegate = UIApplication.shared.delegate as! AppDelegate

        appdelegate.allowRotation="0"

        UIDevice.switchNewOrientation(interfaceOrientation: .portrait)