如何拖动SpriteKit高长精灵时避免其跳转到锚点位置？

方案一：不修改锚点（推荐） #

核心思路是记录触摸点相对于精灵的偏移量，拖动时用触摸位置减去偏移量设置精灵位置，完全规避锚点带来的跳转问题，适配任意锚点设置。

1. 在场景类中声明两个变量：

private var touchOffset: CGPoint = .zero
private var currentTouchedSprite: SKSpriteNode?

2. 实现touchesBegan方法，检测触摸并计算偏移量：

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
    super.touchesBegan(touches, with: event)
    guard let touch = touches.first else { return }
    let touchLocation = touch.location(in: self)
    
    // 检测是否点击到目标精灵（替换为你的monkeySprite）
    if let sprite = nodes(at: touchLocation).first as? SKSpriteNode, sprite == monkeySprite {
        currentTouchedSprite = sprite
        // 计算触摸点相对于精灵锚点的偏移值
        let touchInSprite = touch.location(in: sprite)
        touchOffset = CGPoint(
            x: touchInSprite.x - sprite.anchorPoint.x * sprite.size.width,
            y: touchInSprite.y - sprite.anchorPoint.y * sprite.size.height
        )
    }
}

3. 实现touchesMoved方法，拖动时更新精灵位置：

override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
    super.touchesMoved(touches, with: event)
    guard let touch = touches.first, let sprite = currentTouchedSprite else { return }
    let touchLocation = touch.location(in: self)
    
    // 用触摸位置减去偏移量，保证触摸点始终对应精灵上的初始触摸位置
    sprite.position = CGPoint(
        x: touchLocation.x - touchOffset.x,
        y: touchLocation.y - touchOffset.y
    )
}

4. 实现touchesEnded和touchesCancelled清除触摸状态：

override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
    super.touchesEnded(touches, with: event)
    currentTouchedSprite = nil
}

override func touchesCancelled(_ touches: Set<UITouch>, with event: UIEvent?) {
    super.touchesCancelled(touches, with: event)
    currentTouchedSprite = nil
}

方案二：修改锚点（适合必须调整锚点的场景） #

如果一定要通过修改锚点实现拖动，必须在touchesBegan阶段完成锚点修改和位置校准，避免初始跳转：

1. 声明变量：

private var currentTouchedSprite: SKSpriteNode?

2. 在touchesBegan中修改锚点并校准位置：

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
    super.touchesBegan(touches, with: event)
    guard let touch = touches.first else { return }
    let touchLocation = touch.location(in: self)
    
    if let sprite = nodes(at: touchLocation).first as? SKSpriteNode, sprite == monkeySprite {
        currentTouchedSprite = sprite
        // 计算触摸点对应的新锚点（基于精灵尺寸的比例）
        let touchInSprite = touch.location(in: sprite)
        let newAnchorX = touchInSprite.x / sprite.size.width
        let newAnchorY = touchInSprite.y / sprite.size.height
        
        // 保存精灵当前视觉位置，修改锚点后重新设置位置，避免视觉跳转
        let visualPosition = sprite.position
        sprite.anchorPoint = CGPoint(x: newAnchorX, y: newAnchorY)
        sprite.position = visualPosition
    }
}

3. 在touchesMoved中直接将精灵位置设置为触摸位置：

override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
    super.touchesMoved(touches, with: event)
    guard let touch = touches.first, let sprite = currentTouchedSprite else { return }
    sprite.position = touch.location(in: self)
}

4. 同样需要实现touchesEnded和touchesCancelled清除状态。

原方法出现初始跳转的原因 #

你之前的代码仅在touchesMoved中修改锚点，而初始触摸的touchesBegan阶段未做处理，第一次拖动时精灵仍使用原锚点计算位置，导致视觉跳转。无论采用哪种方案，都必须在触摸开始瞬间完成初始偏移计算或锚点调整。

内容的提问来源于stack exchange，提问作者Dominick