导航项目按钮的大小不起作用

Question

我正在使用xcode 10和swift3。我的导航按钮UI大小不起作用。下面是代码。

extension ListingViewController: MainMenuViewControllerDelegate {
    func successfulLogout() {
        let defaults = UserDefaults.standard
        defaults.removeObject(forKey: "currentID")

        self.currentAgent = nil

        self.findAnAgentButton.title = "LOGIN"
        self.findAnAgentButton.tintColor = UIColor.DefaultButtonColor()
        self.findAnAgentButton.setTitleTextAttributes([NSFontAttributeName: UIFont(name: "Helvetica", size: 16)!], for: .normal)
        self.findAnAgentButton.isEnabled = true
    }
}