SpriteKit - 在 SKAction 期间正确定位精灵

Question

我正在编写一个具有连续（横向）滚动地形的应用程序，它由图像动态组成。所以我创建了一个 sprite，将它横向滚动，当它继续滚动时即将显示其右边缘时，我在它的右侧添加了第二个 sprite，它也会滚动，等等。当它们从左侧消失时，它们'已删除。

问题是当我添加新的精灵时，它和之前的精灵之间有一个小间隙（大约 4 像素），好像在将它放到屏幕上时，滚动动画已经移动了几个像素。

滚动class是这个-

import UIKit
import SpriteKit


private let lagOffset: CGFloat = 4.0 // currently, this is the only way I can get rid of the gap between terrain blocks


class GameScene: SKScene
{
    private var terrainNumber = 2
    private var followingTerrainBlock: TerrainBlock? = .None


    override init(size: CGSize)
    {
        super.init(size: size)

        // create the first terrain block

        let terrainBlock = TerrainBlock(size: Size.terrainBlock, terrainNumber: 1)
        terrainBlock.position = CGPoint(x: size.width / 2.0 + Size.terrainBlock.width, y: size.height / 2.0)

        addChild(terrainBlock)

        followingTerrainBlock = terrainBlock

        moveTerrainBlock(terrainBlock)
    }

    required init?(coder aDecoder: NSCoder)
    {
        fatalError("init(coder:) has not been implemented")
    }


    func moveTerrainBlock(terrainBlock: TerrainBlock)
    {
        // create the next terrain block on a background thread as it's quite expensive
        // it'll be ready in plenty of time for when it's needed

        GCD.async { () -> () in
            self.followingTerrainBlock = TerrainBlock(size: Size.terrainBlock, terrainNumber: self.terrainNumber)
        }


        var targetX = size.width / 2.0
        let y = terrainBlock.position.y

        let move = SKAction.moveTo(CGPoint(x: targetX, y: y), duration: Time.terrainScroll)

        // move the terrain block to centre on the screen - at this point we add the following terrain block immediately behind it, off-screen
        // the scroll animation lasts 5 seconds before the completion closure runs, by which time self.followingTerrainBlock has been ready for ages 

        terrainBlock.runAction(move) { [weak self]() -> Void in

            if let strongSelf = self
            {
                strongSelf.terrainNumber++

                // we have to put an offset into the position of the new terrain block, or there'll be a gap between the old & new blocks

                strongSelf.followingTerrainBlock!.position = CGPoint(x: targetX + Size.terrainBlock.width - lagOffset, y: y)
                strongSelf.addChild(strongSelf.followingTerrainBlock!)

                // now we tell the new terrain block to follow the existing one

                strongSelf.moveTerrainBlock(strongSelf.followingTerrainBlock!)


                // then we continue moving the existing terrain block until it's off-screen, then remove the sprite

                targetX -= Size.terrainBlock.width - lagOffset
                let move = SKAction.moveTo(CGPoint(x: targetX, y: y), duration: Time.terrainScroll)

                terrainBlock.runAction(move) { () -> Void in
                    terrainBlock.removeFromParent()
                }
            }
        }
    }
}

我想知道的是如何将以下地形块放在屏幕上，以便它们与前一个地形块的右边缘完全对齐。如果我停止动画并添加一个，没有偏移的位置是正确的，所以位置计算没有问题。

Answer 1

在创建每个块时，创建一个约束（常量 = 0），将其附加到前一个块...之后的每个块等等。

我相信随着每个块离开视图，约束也会解除分配，但您可能也必须考虑这部分。

SpriteKit - 在 SKAction 期间正确定位精灵

SpriteKit - correct location of sprites during SKAction

sprite-kit

skaction

swift