为什么自定义类视图在第一次平移后不平移？

Question

我有一个自定义类，上面有一个UIPanGestureRecognizer。它在我第一次移动时有效，但是放开后不会记录任何触摸事件。为什么平移手势只能一次执行一次，而不能再次执行？我正在使用Swift 5.1 这是我的代码：

public class FilterConfig
{
    public static void RegisterGlobalFilters(GlobalFilterCollection filters)
    {
        // ...
        filters.Add(new OutputCacheAttribute
        {
            NoStore = true,
            Duration = 0,
            VaryByParam = "*",
            Location = System.Web.UI.OutputCacheLocation.None
        });
    }
}

这是视图控制器：

class ToolPallet: UIView {

// MARK: - Instance Variables

let kCONTENT_XIB_NAME = "ToolPallet"

// MARK: - Outlets

@IBOutlet var contentView: UIView!
@IBOutlet weak var grabberView: UIView! { didSet { grabberView.layer.cornerRadius = grabberView.bounds.width / 2 } }
@IBOutlet weak var grabberImageView: UIImageView! { didSet { grabberImageView.layer.cornerRadius = grabberImageView.bounds.width / 2 } }
@IBOutlet weak var palletView: UIView!


// MARK: - Actions

// some basic IBActions here


// MARK: - Intialization

init(handed: Handed) {
    super.init(frame: CGRect())
    self.handed = handed

    Bundle.main.loadNibNamed(kCONTENT_XIB_NAME, owner: self, options: nil)
    self.autoresizingMask = [.flexibleWidth, .flexibleHeight]
    self.addSubview(contentView)
    translatesAutoresizingMaskIntoConstraints = true
    self.frame = CGRect(x: 40, y: 142, width: 100, height: 481)
}

}