// 重写导航栏返回按钮方法

    func configBackBtn() -> Void {

        // 返回按钮

        let backButton = UIButton(type: .custom)

        // 给按钮设置返回箭头图片

        backButton.setImage(UIImage(named: "NavigationBar_goBack_icon"), for: .normal)

        // 设置frame

        backButton.frame = CGRect(x: 200, y: 13, width: 18, height: 18)

        backButton.addTarget(self, action: #selector(back), for: .touchUpInside)

        // 自定义导航栏的UIBarButtonItem类型的按钮

        let backView = UIBarButtonItem(customView: backButton)

        // 重要方法，用来调整自定义返回view距离左边的距离

        let barButtonItem = UIBarButtonItem(barButtonSystemItem: .fixedSpace, target: nil, action: nil)

        barButtonItem.width = -5

        // 返回按钮设置成功

        navigationItem.leftBarButtonItems = [barButtonItem, backView]

    }