为SKSpriteNode选择随机图像 [英] Choosing random image for SKSpriteNode

问题描述

我正在尝试构建一个简单的障碍跳跃应用程序。我希望从一组图像中随机挑选障碍物的图像。我试过使用arc4random_uniform函数和switch case的组合，但似乎没有更新SKSpriteNode。我做错了什么？

I am trying to build a simple obstacle jumping app. I want the image for the obstacle to be picked randomly from a set of images. I have tried using a combination of the arc4random_uniform function and switch case but that doesn't seem to update the SKSpriteNode. What am i doing wrong?

class PlayScene: SKScene, SKPhysicsContactDelegate{
      ...
      var block3 = SKSpriteNode(imageNamed: "lion")
      ....
}


override func update(currentTime: NSTimeInterval) {
     .....
     blockRunner()
    }


func blockRunner() {

        var imageNamedAnimal = ""
        var randomIndex = arc4random_uniform(2)
        switch(randomIndex) {
        case 0 : imageNamedAnimal = "turtle"
        case 1: imageNamedAnimal = "lion"
        default: imageNamedAnimal = "turtle"
        }

        block3 = SKSpriteNode(imageNamed: imageNamedAnimal)
        .....
        }   

我应该在什么时候尝试设置随机图像？ Block3似乎总是挑选我在代码开头发送的狮子图像，尽管imageNamedAnimal在每个帧中显示随机值。

At what point should i try to set the random image? Block3 seems to pick the lion image always which i had sent at the beginning of the code despite the fact that imageNamedAnimal shows random values in each frame.

推荐答案

通过创建和存储图像作为纹理，每次更改角色时都可以避免加载图像。以下是如何执行此操作的示例：

You can avoid loading the images each time you change the character by creating and storing the images as textures. Here's an example of how to do that:

创建一个数组来存储纹理

Create an array to store the textures

var textures = [SKTexture]()

在 didMoveToView ，创建和存储纹理

textures.append(SKTexture(imageNamed: "turtle"))
textures.append(SKTexture(imageNamed: "lion"))
textures.append(SKTexture(imageNamed: "rhino"))
...

在 blockRunner 方法中，添加以下内容

In the blockRunner method, add the following

 // Randomly select a character
 let rand = Int(arc4random_uniform(UInt32(textures.count)))
 let texture = textures[rand] as SKTexture

 block3.texture = texture
 // Optionally, resize the sprite
 block3.size = texture.size()

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