SKAction.moveByX 没有设置physicsBody.velocity

问题描述

我正在使用 Swift 编写一个 SpriteKit 游戏，并且正在使用以下代码来移动我的精灵 - 但是，它似乎没有更新 velocity.dx:

I'm writing a SpriteKit game using Swift, and am using the following code to move my sprite - however, it doesn't seem to be updating velocity.dx:

func walk(isRight: Bool, speed: Float) {
    var newV = (isRight ? 1 : -1) * 20 * speed;
    let moveAction = SKAction.moveByX(newV, y: 0, duration: 2.0)
    self.runAction(SKAction.repeatActionForever(moveAction), withKey: "walking")
    println("self.physicsBody.velocity.dx: (self.physicsBody.velocity.dx)")
}

这是我在控制台中得到的:

Here's what I get in the console:

self.physicsBody.velocity.dx: 0.0

我需要做些什么来让 moveByX 也更新速度吗?

Is there something I need to do to get the moveByX to also update the velocity?

推荐答案

动作和物理在 SpriteKit 中很大程度上是独立的机制.一般来说，如果你使用物理来移动一个物体，你不应该对它使用移动动作.如果您想移动已经使用物理的物体，请使用物理来移动它——施加力或冲量，或者直接设置它的速度.

Actions and physics are largely separate mechanisms in SpriteKit. Generally, if you're using physics to move a body, you shouldn't use move actions on it. If you want to move a body that's already using physics, use physics to move it -- apply a force or impulse, or set its velocity directly.

相反，当您使用动作来移动身体，或直接设置其position 时，这些更改不会通过物理引擎.如果你想在一个移动动作中找到一个节点的速度，你必须自己通过观察它在帧之间的位置变化来计算它.

Conversely, when you use actions to move a body, or set its position directly, those changes don't go through the physics engine. If you want to find the speed of a node during a move action, you'll have to calculate it yourself by observing the change in its position between frames.

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