使用UIPanGestureRecognizer更新约束

import UIKit

class ViewController: UIViewController {
    
    let draggableView = UIView()
    var initialCenter: CGPoint = .zero
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        draggableView.backgroundColor = .blue
        draggableView.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(draggableView)
        
        NSLayoutConstraint.activate([
            draggableView.centerXAnchor.constraint(equalTo: view.centerXAnchor),
            draggableView.centerYAnchor.constraint(equalTo: view.centerYAnchor),
            draggableView.widthAnchor.constraint(equalToConstant: 100),
            draggableView.heightAnchor.constraint(equalToConstant: 100)
        ])
        
        let panGesture = UIPanGestureRecognizer(target: self, action: #selector(handlePan(_:)))
        draggableView.addGestureRecognizer(panGesture)
    }
    
    @objc func handlePan(_ gesture: UIPanGestureRecognizer) {
        let translation = gesture.translation(in: view)
        
        switch gesture.state {
        case .began:
            initialCenter = draggableView.center
        case .changed:
            draggableView.center = CGPoint(x: initialCenter.x + translation.x, y: initialCenter.y + translation.y)
        case .ended, .cancelled:
            // 可以在这里添加动画或其他结束时的处理
            break
        default:
            break
        }
    }
}