仅在x轴上移动Sprite

Question

I am working with Ray Wenderlich's 2D Game Development Book and I make use of a function out of this book to control the movement of a sprite, here called 'passenger'. The example in the book is moving the sprite on ax and y axis, where as I only would need to move the sprite along the x axis, but I can not get it working.

Here is 'my' code - well the code I am using

    func move(sprite: SKSpriteNode, velocity: CGPoint){        
    let amountToMove = CGPoint(x: velocity.x * CGFloat(dt),
                               y: velocity.y * CGFloat(dt))
    sprite.position = CGPoint(
        x: sprite.position.x + amountToMove.x,
        y: sprite.position.y + amountToMove.y)
}

func movePassengerToward(location: CGPoint) {        
    let offset = CGPoint(x: location.x - passenger.position.x, y: location.y - passenger.position.y)
    let length = sqrt(Double(offset.x * offset.x + offset.y * offset.y))
    let direction = CGPoint(x: offset.x / CGFloat(length),
                            y: offset.y / CGFloat(length))
    velocity = CGPoint(x: direction.x * passengerMovePointsPerSec,
                       y: direction.y * passengerMovePointsPerSec)        
}

and I trigger these functions from the update loop like this:

if let lastTaxiLocation = lastTaxiLocation {
let diff = lastTaxiLocation - passenger.position
if diff.length() <= passengerMovePointsPerSec * CGFloat(dt){
    passenger.position = lastTaxiLocation
    velocity = CGPoint.zero
} else {
    move(sprite: passenger, velocity: velocity)
    print("update loop")
    }
}

Does anyone have an idea for this issue?

Answer 1

尝试仅在move功能中设置X组件：

sprite.position.x = sprite.position.x + amountToMove.x