在 viewdidload 之外更新導航欄按鈕項目標題

Question

我正在使用以下代碼在viewDidLoad方法中創建一個導航欄：

   let backButtonImage = UIImage(named: "backButton")
    normalButton = UIButton(frame: CGRect(x: 0, y: 0, width: backButtonImage!.size.width, height: backButtonImage!.size.height))
    normalButton.setImage(backButtonImage, for: .normal)

    normalButton.setTitleColor(.systemBlue, for: .normal)
    normalButton.contentHorizontalAlignment = .leading
    normalButton.contentVerticalAlignment = .center
    normalButton.titleEdgeInsets = UIEdgeInsets(top: 0, left: 0.0, bottom: 0.0, right: 0.0)

    let backBarButton = UIBarButtonItem(customView: normalButton)
    backBarButton.tintColor = .systemBlue


    item.leftBarButtonItems = [backBarButton]

    navigationBar.isTranslucent = false
    navigationBar.barTintColor = .white

    self.view.addSubview(navigationBar)
    navigationBar.translatesAutoresizingMaskIntoConstraints = false

    navigationBar.leftAnchor.constraint(equalTo: view.leftAnchor).isActive = true
    navigationBar.rightAnchor.constraint(equalTo: view.rightAnchor).isActive = true
    navigationBar.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor).isActive = true



    navigationBar.items = [item]
    navigationBar.delegate = self

但是我想在用戶觸摸視圖內的另一個按鈕時更新 normalButton 標題。 我嘗試了以下代碼：

    if let letnavItem = navigationBar.items?[0],let bb = letnavItem.leftBarButtonItems?[0] {
        if let but = bb.customView, let but2 = but as? UIButton {
            print("counter: \(counter)")
            but2.setTitle("asd", for: .normal)
        }
    }

但它不起作用。 但是如果我在 navigationBar.delegate 行之后在viewDidLoad方法中運行第二個代碼，它運行良好。

為什么它不能在viewDidLoad之外工作？

Answer 1

以上所有代碼都是正確的，只是您需要在設置按鈕文本之前從按鈕中刪除圖像，如下所示：

but2.setImage(nil, for: .normal)
but2.setTitle("asd", for: .normal)