预先设定的节点不与用户触摸的创建的节点

Question

例碰撞（在屏幕上的红色块），

var img = "BlockRed.png" 
let sand = SKSpriteNode (imageNamed: img) 
var randLoc = arc4random_uniform(26) 
sand.position = CGPointMake(location.x - CGFloat(10) + CGFloat(randLoc), location.y) 
sand.name = "redSand" 
sand.zPosition = 0 
self.addChild(sand) 

//gravity 
sand.physicsBody?.affectedByGravity = true 

//contact 
sand.physicsBody!.categoryBitMask = PARTICLE 
sand.physicsBody?.collisionBitMask = BLOCK | PARTICLE 
sand.physicsBody?.contactTestBitMask = BLOCK | PARTICLE 
sand.physicsBody = SKPhysicsBody(circleOfRadius: sand.frame.width - 3) 

但是，当它们接触时，颗粒刚好落在壁上。为什么会发生这种情况，我该如何解决？

注：

// Constants 
let NOTHING: UInt32 = 0x1 << 0 
let PARTICLE: UInt32 = 0x1 << 1 
let BLOCK: UInt32  = 0x1 << 2 

Answer 1

预设节点的物理主体不是基于体积的物体，因此不会与沙粒碰撞。我从切换：

preWall.physicsBody = SKPhysicsBody(edgeLoopFromRect: CGRect(x: x, y: y, width: width, height: height)) 

到

preWall.physicsBody = SKPhysicsBody(rectangleOfSize: preWall.frame.size) 

Answer 2

您初始化沙子颗粒的physics body您设置的bit masks后。尝试改变线条的顺序。

sand.physicsBody = SKPhysicsBody(circleOfRadius: sand.frame.width - 3) 
sand.physicsBody?.categoryBitMask = PARTICLE 
sand.physicsBody?.collisionBitMask = BLOCK | PARTICLE 
sand.physicsBody?.contactTestBitMask = BLOCK | PARTICLE