如何通過觸摸來旋轉SpriteNode？

如何在觸摸的固定點上旋轉SpriteKit節點。所以當用戶拖動他的手指時就會變成。我也希望能夠獲得轉速。（這個問題被問過，但我想知道如何使用SpriteKit做）斯威夫特3個操場如何通過觸摸來旋轉SpriteNode？

我有這個迄今爲止其工作，但有時我得到一個錯誤的變種deltaAngle =角 - startingAngle！錯誤 - 「意外發現零而展開可選值」

class GameScene: SKScene { 
var startingAngle:CGFloat? 
var startingTime:TimeInterval? 


override func didMove(to view: SKView) { 
    let wheel = SKSpriteNode(imageNamed: "IMG_6797.PNG") 

    wheel.position = CGPoint(x: 200, y: 200) 

    wheel.name = "wheel" 
    wheel.setScale(0.5) 
    wheel.physicsBody = SKPhysicsBody(circleOfRadius: wheel.size.width/2) 
    // Change this property as needed (increase it to slow faster) 
    wheel.physicsBody!.angularDamping = 4 
    wheel.physicsBody?.pinned = true 
    wheel.physicsBody?.affectedByGravity = false 
    addChild(wheel) 
} 

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) { 
    for touch in touches { 
     let location = touch.location(in:self) 
     let node = atPoint(location) 
     if node.name == "wheel" { 
      let dx = location.x - node.position.x 
      let dy = location.y - node.position.y 
      // Store angle and current time 
      startingAngle = atan2(dy, dx) 
      startingTime = touch.timestamp 
      node.physicsBody?.angularVelocity = 0 
     } 
    } 
} 

override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) { 
    for touch in touches{ 
     let location = touch.location(in:self) 
     let node = atPoint(location) 
     if node.name == "wheel" { 
      let dx = location.x - node.position.x 
      let dy = location.y - node.position.y 


      let angle = atan2(dy, dx) 
      // Calculate angular velocity; handle wrap at pi/-pi 
      var deltaAngle = angle - startingAngle! 
      if abs(deltaAngle) > CGFloat.pi { 
       if (deltaAngle > 0) { 
        deltaAngle = deltaAngle - CGFloat.pi * 2 
       } 
       else { 
        deltaAngle = deltaAngle + CGFloat.pi * 2 
       } 
      } 
      let dt = CGFloat(touch.timestamp - startingTime!) 
      let velocity = deltaAngle/dt 

      node.physicsBody?.angularVelocity = velocity 

      startingAngle = angle 
      startingTime = touch.timestamp 
     } 
    } 
} 



override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) { 

    startingAngle = nil 
    startingTime = nil 
}

}

來源

2017-03-31 David Williamson

附加保護你嘗試過這麼遠嗎？ ;） – Whirlwind

我最初打算使用UIKit（UiGestureRecogniser），但我在我的wwdc遊樂場中使用的SpriteKit太少，需要添加更多。我是SpriteKit的新手，所以不知道該怎麼做@Whirlwind –

你應該使用touchesBegan和touchesMoved覆蓋來獲取觸摸位置，然後計算節點應該旋轉到的切線角度。對於初學者來說，請確保您的節點圖形資源面向右側，否則您的角度將會關閉。如果您仍然需要幫助，請從那裏開始並返回一些代碼。 – TheValyreanGroup

這錯誤意味着正是它說。最有可能的是，「wheel」在touchesBegan中沒有被觸及，但是隨後在touchesMoved中註冊，導致startingAngle不被設置爲任何事物並且零。

因爲你很可能不希望自己的車輪旋轉，如果用戶沒有啓動摸上方向盤，我會在touchedMoved

... 
let angle = atan2(dy, dx) 

guard startingAngle != nil else {return} //Exit the function if starting angle was never set 

var deltaAngle = angle - startingAngle! 
...

來源

2017-04-02 14:23:35 TheValyreanGroup

如果用戶輕彈它，代碼旋轉輪，你怎麼能得到它隨着用戶拖動他的手指轉動？ –

如何通過觸摸來旋轉SpriteNode？

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