Swift - 以编程方式在 UIStackView 中创建 UIPickerView

Question

我是一个完整的 swift 和 iOS 开发初学者，所以对我很容易:)
在我的应用程序中，我有一个水平的 StackView。
在该 StackView 中 - 我有一个标签和一个按钮，现在我想添加一个PickerView，它将从一些选项列表中填充。
我一直在谷歌搜索和阅读线程，但我得到的最接近的是让 PickerView 显示它的位置（使用一些背景颜色）但里面没有实际值。
这是我创建和自定义 StackView 组件的代码：

class SingleReportInputStackView: UIStackView {
    ...  // creating and customizing my StackView


    private func getObjects() -> (UILabel, UIButton, UIPickerView) {
        let myLabel: UILabel = {
            ...  // creating UILabel
        }()
        
        let myButton: UIButton = {
            ... // creating UIButton
        }()
        
        class MyPicker: NSObject, UIPickerViewDelegate, UIPickerViewDataSource {
            let dataArray = ["English", "Maths", "History", "German", "Science"]
            let UIPicker: UIPickerView = UIPickerView()
            
            override init() {
                super.init()
                self.UIPicker.delegate = self
                self.UIPicker.dataSource = self
                self.UIPicker.backgroundColor = UIColor.white
            }
            
            func numberOfComponents(in pickerView: UIPickerView) -> Int {
                return 1
            }
            
            func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
                return dataArray.count
            }
            
            func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
                let row = dataArray[row]
                return row
            }
        }
        
        let myPicker = MyPicker()
        return (myLabel, myButton, myPicker.UIPicker)
    }
    ...
}

然后，我通过调用setupSingleInput()将这些组件添加到我的 Horizo​​ntal StackView 中：

class SingleReportInputStackView: UIStackView {
    ...
    private func setupSingleInput() {
        let (myLabel, myButton, myPicker) = getObjects()
        self.addArrangedSubview(myLabel)
        self.addArrangedSubview(myButton)
        self.addArrangedSubview(myPicker)
        self.translatesAutoresizingMaskIntoConstraints = false
    }
    ...
}

正如我所说，我可以看到标签、按钮和 PickerView 的白色背景（看起来像一个空的白色矩形）。

顺便说一句，我没有故事板（如果这还不是很明显） - 我正在以编程方式创建 UI。

有人可以帮我吗？ 为什么我的 PickerView 没有被我的 dataArray 正确填充？

Answer 1

总的来说，我是 swift 和 iOS 开发的完整初学者......

我建议开始更简单一些......在func嵌入一​​个class几乎肯定不是这里的方法。

最大的问题是您在getObjects()函数中创建了一个MyPicker实例，但是随后您从该类返回了一个 UI 元素，并且类实例消失了——它超出了范围：

private func getObjects() -> (UILabel, UIButton, UIPickerView) {
    // ... all the stuff you're doing in here

    let myPicker = MyPicker()

    // as soon as you return, myPicker no longer exists!!!

    return (myLabel, myButton, myPicker.UIPicker)
}

因此，您返回了一个UIPickerView ，但它不再有任何代码（它的 Delegate 和 DataSource）支持它。

这是一个快速修改：

class SingleReportInputStackView: UIStackView {
    
    private var myPicker: MyPicker!
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        setupSingleInput()
    }
    required init(coder: NSCoder) {
        super.init(coder: coder)
        setupSingleInput()
    }
    private func setupSingleInput() {
        let (myLabel, myButton) = getObjects()
        myPicker = MyPicker()
        self.addArrangedSubview(myLabel)
        self.addArrangedSubview(myButton)
        self.addArrangedSubview(myPicker.UIPicker)
        self.translatesAutoresizingMaskIntoConstraints = false
    }
    
    private func getObjects() -> (UILabel, UIButton) {
        let myLabel: UILabel = {
            let v = UILabel()
            v.text = "The Label"
            return v
        }()
        
        let myButton: UIButton = {
            let v = UIButton(type: .system)
            v.setTitle("The Button", for: [])
            return v
        }()
        
        return (myLabel, myButton)
    }
    
    private class MyPicker: NSObject, UIPickerViewDelegate, UIPickerViewDataSource {
        let dataArray = ["English", "Maths", "History", "German", "Science"]
        let UIPicker: UIPickerView = UIPickerView()
        
        override init() {
            super.init()
            self.UIPicker.delegate = self
            self.UIPicker.dataSource = self
            self.UIPicker.backgroundColor = UIColor.white
        }
        
        func numberOfComponents(in pickerView: UIPickerView) -> Int {
            return 1
        }
        
        func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
            return dataArray.count
        }
        
        func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
            let row = dataArray[row]
            return row
        }
    }
    
}

和一个示例视图控制器来尝试它：

class UriYakirViewController: UIViewController {
    
    let singleReportStack = SingleReportInputStackView()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // a yellow-ish background so we can see the white picker view frame
        view.backgroundColor = UIColor(red: 1.0, green: 0.8, blue: 0.5, alpha: 1)
        
        view.addSubview(singleReportStack)
        
        singleReportStack.axis = .vertical
        
        let g = view.safeAreaLayoutGuide
        NSLayoutConstraint.activate([
            singleReportStack.centerXAnchor.constraint(equalTo: g.centerXAnchor),
            singleReportStack.centerYAnchor.constraint(equalTo: g.centerYAnchor),
        ])
        
    }
    
}

该代码将为您提供以下结果：