swift - SpriteKit 碰撞检测未按预期工作

Question

所以我在我的GameScene班级中有这段代码（的孩子SKScene）：

physicsWorld.contactDelegate = self
physicsWorld.gravity = CGVector(dx: 0, dy: -9.8)
addChild(balloon)
addChild(monkey)
monkey.physicsBody = SKPhysicsBody(rectangleOf: monkey.frame.size)
monkey.physicsBody?.isDynamic = false
monkey.physicsBody?.categoryBitMask = 0
monkey.physicsBody?.contactTestBitMask = 1//Balloon.categoryBitMask

balloon.physicsBody = SKPhysicsBody(rectangleOf: balloon.frame.size)
balloon.physicsBody?.isDynamic = false
balloon.physicsBody?.categoryBitMask = 1
balloon.physicsBody?.contactTestBitMask = 0
balloon.start()

我可以看到气球和猴子节点在模拟器中已经相互接触，但是没有任何反应。我也遵守了SKPhysicsContactDelegate协议，如下所示：

extension GameScene: SKPhysicsContactDelegate {
    func didBegin(_ contact: SKPhysicsContact) {
        print("CONTACT!!!")
    }
}

编辑：我设置isDynamic = true并打印“联系！！” 正如预期的那样，但是我不希望物体影响彼此的位置