iOS 13中的Uitassintitem如何与自定义inputView一起工作？

我有一个带有一个文本字段的视图控制器，我将文本字段用于键盘快捷键栏的每个组（前导和尾随）的按钮，简单如下：

class MyViewController: UIViewController {

    @IBOutlet weak var textField: UITextField!

    override func viewDidLoad() {
        super.viewDidLoad()

        setupKeypad()
    }

    private func setupKeypad() {
        let item: UITextInputAssistantItem = textField.inputAssistantItem
        let doneButton = UIButton()
        doneButton.setTitle("done", for: .normal)
        doneButton.addTarget(self, action: #selector(donePressed), for: .touchUpInside)

        let cancelButton = UIButton()
        cancelButton.setTitle("cancel", for: .normal)
        cancelButton.addTarget(self, action: #selector(cancelPressed), for: .touchUpInside)

        let rightBarButtonItem = UIBarButtonItem(customView: doneButton)
        let leftBarButtonItem = UIBarButtonItem(customView: cancelButton)

        let leftGroup = UIBarButtonItemGroup(barButtonItems: [leftBarButtonItem], representativeItem: nil)
        let rightGroup = UIBarButtonItemGroup(barButtonItems: [rightBarButtonItem], representativeItem: nil)

        item.leadingBarButtonGroups = [leftGroup]
        item.trailingBarButtonGroups = [rightGroup]
    }

    @objc func donePressed() {
        print(#function)
    }

    @objc func cancelPressed() {
        print(#function)
    }
}

没有什么特别的，只需在

viewDidLoad（）

方法中调用

setupKeypad（）

即可添加这两个按钮。它工作正常：

但是，当尝试为文本字段添加自定义

inputView

时，快捷键栏不再显示：

override func viewDidLoad() {
    super.viewDidLoad()

    // adding dummy custom view as inputView for the textField
    let customView = UIView(frame: CGRect(x: 0, y: 0, width: 300.0, height: 300.0))
    customView.backgroundColor = .orange
    textField.inputView = customView

    setupKeypad()
}

结果是：

我在以前的iOS版本（12.4-）上仔细检查了它，它在自定义

inputview

中运行良好。例如，iOS 12.2的结果是：

如何解决这个问题