检测UIPickerView何时开始更改/移动

UIPickerView hitTest(point:with:) . 创建协议时,您可以通过委托方法将当前选择器发送到控制器,并绘制任意内容:

protocol CustomPickerViewDelegate: class {
    func didTapped(_ picker: CustomPickerView)
}

class CustomPickerView: UIPickerView {

    weak var myDelegate: CustomPickerViewDelegate?

    override func hitTest(_ point: CGPoint, with event: UIEvent?) -> UIView? {
        // Only test for points in your needed view
        if !self.point(inside: point, with: event) {
            return nil
        }

        // Return using CustomPickerViewDelegate the current picker
        // that can be used to determine which one was selected
        myDelegate?.didTapped(self)

        // Call super.hitTest(_: with:)
        return super.hitTest(point, with: event)
    }
}

别忘了(在你的控制器里:例如。 YourViewController ):

self.pickerView.myDelegate = self .

创建订阅的控制器的扩展 CustomPickerViewDelegate 协议:

extension YourViewController: CustomPickerViewDelegate {
    func didTapped(_ picker: CustomPickerView) {
        // do what you want here
        self.addBorderTo(picker: picker)
    }
}

UIPickerViewDelegate (请参见下面如何扩展基类委托)

Extending a delegate from a base class

祝你好运:]