make SKPhysicsBody unidirectional

Question

我有一个SKSpriteNode球，它被赋予了所有SKPhysicsBody属性向各个方向移动。我现在想要的是让它unidirectional(只朝着它以前没有移动的方向前进，而不是回到它曾经前进过的道路上(。目前我对这个问题有以下想法，

• 做一个fieldBitMask，到它迭代的路径并排斥 球不回去
• 从touchesBegan/ touchesMoved方法对球施加某种force/ impulses以防止它回去
• 可以用update方法处理的东西
• 来自StackFlowOverflow的救生员，即使在周末:)也编码

支持代码片段以便更好地理解，

//getting current touch position by using UIEvent methods
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
guard let touch = touches.first else {return}
let location = touch.location(in: self)
lastTouchPoint = location
}
override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
guard let touch = touches.first else {return}
let location = touch.location(in: self)
lastTouchPoint = location
}
override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
lastTouchPoint = nil
}
override func touchesCancelled(_ touches: Set<UITouch>, with event: UIEvent?) {
lastTouchPoint = nil
}
//ball created
func createPlayer(){
player = SKSpriteNode(imageNamed: "player")
player.position = CGPoint(x: 220, y: 420)
player.zPosition = 1
//physics for ball
player.physicsBody = SKPhysicsBody(circleOfRadius: player.size.width / 2)
player.physicsBody?.allowsRotation = false
player.physicsBody?.linearDamping =  0.5

player.physicsBody?.categoryBitMask = collisionTypes.player.rawValue
player.physicsBody?.contactTestBitMask = collisionTypes.finish.rawValue
player.physicsBody?.collisionBitMask = collisionTypes.wall.rawValue
addChild(player)
}
//unwarp the optional property, calclulate the postion between player touch and current ball position
override func update(_ currentTime: TimeInterval) {
guard isGameOver == false else { return }
if let lastTouchPosition = lastTouchPoint {
//this usually gives a large value (related to screen size of the device) so /100 to normalize it
let diff = CGPoint(x: lastTouchPosition.x - player.position.x, y: lastTouchPosition.y - player.position.y)
physicsWorld.gravity = CGVector(dx: diff.x/100, dy: diff.y/100)
}
}

Answer 1

嗯，这是touchesBegan/ touchesMoved和update功能的组合小技巧，

首先，您需要了解发生了哪个触摸，获取它的名称(在我的 案例我制作的节点的alpha为0，但在 在它们上方移动，即阿尔法 1(。touchesBegan, touchesMoved如下

guard let touch = touches.first else {return}
let location = touch.location(in: self)
lastTouchPoint = location
let positionInScene = touch.location(in: self)
let touchedNode = self.atPoint(positionInScene)
if let name = touchedNode.name
{
if name == "vortex"
{
touching = false
self.view!.isUserInteractionEnabled = false
print("Touched on the interacted node")
}else{
self.view!.isUserInteractionEnabled = true
touching = true
}
}
}

第二次使用BOOL touching跟踪用户交互，通过使用获取点击识别器设置在屏幕上，如下所示

func setupTapDetection() {
let t = UITapGestureRecognizer(target: self, action: #selector(tapped(_:)))
view?.addGestureRecognizer(t)
}
@objc func tapped(_ tap: UITapGestureRecognizer) {
touching = true
}

最后在update进行如下检查，

guard isGameOver == false else { return }
self.view!.isUserInteractionEnabled = true
if(touching ?? true){
if let lastTouchPosition = lastTouchPoint {
//this usually gives a large value (related to screen size of the device) so /100 to normalize it
let diff = CGPoint(x: lastTouchPosition.x - player.position.x, y: lastTouchPosition.y - player.position.y)
physicsWorld.gravity = CGVector(dx: diff.x/100, dy: diff.y/100)
}
}
}