swift 4 : SKSpriteNode won't stop on a position

Question

这里我有一辆装有子弹的坦克，当用户点击屏幕时，坦克开火，没关系

但是当子弹从坦克中射出时，它会飞到屏幕上方，并且不会停在触摸位置

这是我的代码:

for touch in touches {
        let location = touch.location(in: self)

        let bullet = SKSpriteNode(imageNamed: "bullet4")

        bullet.position = CGPoint(x: self.MainTank.position.x, y: self.MainTank.position.y + 10)

        bullet.size = CGSize(width: 12, height: 20)

        bullet.physicsBody = SKPhysicsBody(circleOfRadius: bullet.size.width / 2)

        bullet.physicsBody?.affectedByGravity = false
        bullet.physicsBody?.isDynamic = true // false stops the bullet on the tank
        bullet.physicsBody?.allowsRotation = false
        self.addChild(bullet)

        var dx = CGFloat(location.x)
        var dy = CGFloat(location.y)

        let magnitude = sqrt(dx * dx + dy * dy)

        dx /= magnitude
        dy /= magnitude

        let vector  = CGVector(dx: 5.0 * dx, dy: 5.0 * dy)

        bullet.physicsBody?.applyImpulse(vector)


}

我尝试将isDynamic设置为true，但这会使子弹停在坦克位置

谢谢

Answer 1

它可能会移动到屏幕之外，因为您将向量乘以 5.0。我也不会像那样创建你的向量，因为不需要带有大小的除法部分。试试这个:

let dx = location.x - bullet.position.x
let dy = location.y - bullet.position.y
let vector  = CGVector(dx: dx, dy: dy)
bullet.run(SKAction.move(by: vector, duration: 1.0)) //choose your own duration of course