如何在存在重力的情况下拖动和轻击SpriteKit中的节点？

import SpriteKit

class GameScene: SKScene {
    var draggableNode: SKSpriteNode!
    
    override func didMove(to view: SKView) {
        // 创建一个可拖动的节点
        draggableNode = SKSpriteNode(color: .red, size: CGSize(width: 100, height: 100))
        draggableNode.position = CGPoint(x: frame.midX, y: frame.midY)
        draggableNode.physicsBody = SKPhysicsBody(rectangleOf: draggableNode.size)
        draggableNode.physicsBody?.isDynamic = true
        draggableNode.isUserInteractionEnabled = true
        addChild(draggableNode)
        
        // 添加重力效果
        physicsWorld.gravity = CGVector(dx: 0, dy: -9.8)
    }
    
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        // 记录触摸点的位置
        if let touch = touches.first {
            let location = touch.location(in: self)
            draggableNode.userData = NSMutableDictionary()
            draggableNode.userData?.setValue(location, forKey: "touch")
        }
    }
    
    override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
        // 计算触摸点的偏移量，并更新节点的位置
        if let touch = touches.first, let touchLocation = draggableNode.userData?.value(forKey: "touch") as? CGPoint {
            let location = touch.location(in: self)
            let offset = CGPoint(x: location.x - touchLocation.x, y: location.y - touchLocation.y)
            draggableNode.position = CGPoint(x: draggableNode.position.x + offset.x, y: draggableNode.position.y + offset.y)
            draggableNode.userData?.setValue(location, forKey: "touch")
        }
    }
    
    override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
        // 清除触摸点的记录
        draggableNode.userData?.removeObject(forKey: "touch")
    }
    
    override func touchesCancelled(_ touches: Set<UITouch>, with event: UIEvent?) {
        // 清除触摸点的记录
        draggableNode.userData?.removeObject(forKey: "touch")
    }
    
    override func touchesEstimatedPropertiesUpdated(_ touches: Set<UITouch>) {
        // 处理多点触摸
    }
    
    override func touchesShouldBegin(_ touches: Set<UITouch>, with event: UIEvent?, in view: UIView) -> Bool {
        // 控制触摸是否被接收
        return true
    }
    
    override func touchesShouldCancel(in view: UIView) -> Bool {
        // 控制触摸是否被取消
        return true
    }
    
    override func update(_ currentTime: TimeInterval) {
        // 游戏循环更新
    }
}