PickerView调用点击时间

PickerView可以通过实现`UIPickerViewDelegate`中的`pickerView(_:didSelectRow:inComponent:)`方法来响应用户的点击事件。该方法会在用户点击PickerView中某一行时被调用，参数`row`表示用户所选行的索引，而参数`component`表示用户所选列的索引。例如，下面的代码展示了一个PickerView，并在用户点击某一行时弹出一个UIAlertController提示框。

class MyViewController: UIViewController, UIPickerViewDelegate {
    
    let data = ["Option 1", "Option 2", "Option 3"]
    var pickerView: UIPickerView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        pickerView = UIPickerView()
        pickerView.delegate = self
        view.addSubview(pickerView)
    }
    
    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        
        pickerView.frame = CGRect(x: 0, y: 100, width: view.bounds.width, height: 200)
    }
    
    func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
        let alertController = UIAlertController(title: "Selected", message: "You selected \(data[row])", preferredStyle: .alert)
        let okAction = UIAlertAction(title: "OK", style: .default, handler: nil)
        alertController.addAction(okAction)
        present(alertController, animated: true, completion: nil)
    }
    
    func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
        return data[row]
    }
    
    func numberOfComponents(in pickerView: UIPickerView) -> Int {
        return 1
    }
    
    func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        return data.count
    }
}