使用未正确设置的UIButton框架创建的Swift UIBarButtonItem

Question

我需要显示一个包含3个元素的工具栏（两侧各有两个按钮，中间有一个标签）。它们中的每一个都是使用自定义UIButton创建的。这是代码：

 let toolBar = UIToolbar()
        toolBar.barStyle = .default
        toolBar.sizeToFit()

        let titleButton = UIButton(type: .custom)
        titleButton.titleLabel?.numberOfLines = 0
        titleButton.setTitle(self.toolBarLabelString, for: UIControlState.normal)
        titleButton.setTitleColor(.darkGray, for: .normal)
        titleButton.frame = CGRect.init(x: 0, y: 0, width: self.view.frame.width - 180, height: 40)
        titleButton.contentEdgeInsets = UIEdgeInsets(top: 0, left: 20.0, bottom: 0, right: -14.0)
        //titleButton.backgroundColor = .yellow

        let doneButton = UIButton(type: .custom)
        doneButton.setTitle("Done", for: UIControlState.normal)
        doneButton.frame = CGRect.init(x: 0, y: 0, width: 40, height: 40)
        doneButton.contentEdgeInsets = UIEdgeInsets(top: 0, left: 0.0, bottom: 0, right: -24.0)
        doneButton.setTitleColor(.green, for: .normal)
        doneButton.addTarget(self, action: #selector(CreateRecipeViewController.donePicker), for: .touchUpInside)
        //doneButton.backgroundColor = .yellow

        let cancelButton = UIButton(type: .custom)
        cancelButton.frame = CGRect.init(x: 0, y: 0, width: 40, height: 40)
        cancelButton.contentEdgeInsets = UIEdgeInsets(top: 0, left: -14.0, bottom: 0, right: 0)
        cancelButton.setTitle("Cancel", for: UIControlState.normal)
        cancelButton.setTitleColor(.red, for: .normal)
        cancelButton.addTarget(self, action: #selector(CreateRecipeViewController.cancelPicker), for: .touchUpInside)


        let titleBarButton = UIBarButtonItem(customView: titleButton)
        let spaceButton = UIBarButtonItem(barButtonSystemItem: UIBarButtonSystemItem.fixedSpace, target: nil, action: nil)
        spaceButton.width = 20

        let cancelBarButton = UIBarButtonItem(customView: cancelButton)
        //let cancelBarButton = UIBarButtonItem(barButtonSystemItem : .cancel, target: nil, action:  #selector(CreateRecipeViewController.cancelPicker))
        //let doneBarButton = UIBarButtonItem(barButtonSystemItem : .done, target: nil, action:  #selector(CreateRecipeViewController.donePicker))
        let doneBarButton =  UIBarButtonItem(customView: doneButton)

        toolBar.setItems([cancelBarButton, spaceButton, titleBarButton, spaceButton, doneBarButton], animated: false)
        toolBar.isUserInteractionEnabled = true

我看到两侧的按钮没有显示，因为它们与中心元素重叠。我尝试设置一个框架和contenEdgeInsets，但这没有帮助。

我将非常感谢您的任何帮助/想法。

谢谢！