ios - 用户触摸后线路旋转

Question

我很难弄清楚应该如何创建一条从 A 点出发并指向 B 点(用户的手指)或更远的线。这样的行可能看起来像

(A) 原点 (B) 手指

A--------B------------

这条线会延伸到屏幕之外，并且当用户移动手指时应该旋转。创建直线并实时移动其 B 坐标的代码也会有所帮助。谢谢!

编辑 - 到目前为止我所做的:

class GameScene: SKScene {
     let testball = SKShapeNode(circleOfRadius: 50)
     let testguy = SKShapeNode(circleOfRadius: 50)
     let line = SKShapeNode()
     let pathToDraw = CGPathCreateMutable()


override func didMoveToView(view: SKView) {
    self.backgroundColor = UIColor(colorLiteralRed: 0.9, green: 0.9, blue: 1, alpha: 0.5)
    testball.fillColor = UIColor.redColor()
    self.addChild(testball)

    self.testguy.position = CGPointMake(CGRectGetMinX(self.frame) + testguy.frame.width + 10, CGRectGetMinY(self.frame) + testguy.frame.height + 10)
    self.testguy.fillColor = SKColor.redColor()
    self.addChild(self.testguy)

    CGPathMoveToPoint(pathToDraw, nil, testguy.position.x, testguy.position.y)
    self.addChild(self.line)

}

override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {

    testball.position = (touches.first?.locationInNode(self))!

    CGPathAddLineToPoint(pathToDraw, nil, (touches.first?.locationInNode(self).x)!, (touches.first?.locationInNode(self).y)!)
    self.line.path = pathToDraw
    self.line.strokeColor = UIColor.redColor()

}

override func touchesMoved(touches: Set<UITouch>, withEvent event: UIEvent?) {
    testball.position = (touches.first?.locationInNode(self))!
    //print(touches.first?.locationInView(self.view), appendNewline: true);

    line.removeFromParent()

    testball.position = (touches.first?.locationInNode(self))!

    CGPathAddLineToPoint(pathToDraw, nil, (touches.first?.locationInNode(self).x)!, (touches.first?.locationInNode(self).y)!)
    self.line.path = pathToDraw
    self.line.strokeColor = UIColor.redColor()
    self.addChild(line)
}

Answer 1

我明白了!我所要做的就是将 touchesBegan 和 touchesMoved 中的代码更改为

    line.removeFromParent()

    testball.position = (touches.first?.locationInNode(self))!

    let pathToDraw = CGPathCreateMutable()
    CGPathMoveToPoint(pathToDraw, nil, testguy.position.x, testguy.position.y)
    CGPathAddLineToPoint(pathToDraw, nil, (touches.first?.locationInNode(self).x)!, (touches.first?.locationInNode(self).y)!)

    self.line.path = pathToDraw
    self.line.strokeColor = UIColor.redColor()

    self.addChild(self.line)

在touchesEnded内部，我编写了self.line.removeFromParent()，以便在用户触摸屏幕后删除该行。