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Misunderstanding layer approach ! — Gideros Forum
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    Misunderstanding layer approach !

    mefistomefisto Member
    edited December 2012 in Game & application design
    The topic, Support for something like layers? "http://www.giderosmobile.com/forum/discussion/170/support-for-something-like-layers" suggest that using sprite as a layer is just fine. So i tested fallowing code but gives me static ball on screen position 400,100! Then i activated box2d debug mode it shows me that ball is falling down normally against gravity but image stay at initial position. Most probably i misunderstanding layer approach or i am missing a point. Can someone clarify to me?
     --include box2d library
require "box2d"
 
game = gideros.class(Sprite)
 
--on game initialization
function game:init()
 
 
	self.world= b2.World.new(0,10,true)
 
	--run world
	self:addEventListener(Event.ENTER_FRAME, self.onEnterFrame, self)
	--remove event on exiting game
	self:addEventListener("exitBegin", self.onExitBegin, self)
 
	local debugDraw = b2.DebugDraw.new()
	self.debugDraw=debugDraw
	self.world:setDebugDraw(debugDraw)
	self:addChild(debugDraw)
 
 
	self.layer=Sprite.new()
	self:addChild(self.layer)
 
	local bbody = self.world:createBody{type = b2.DYNAMIC_BODY,position ={x=200, y=10}}
	local shotball = Bitmap.new(Texture.new("images/ball.png"))
 
	local bradius = shotball:getWidth()/2
	local bcircle = b2.CircleShape.new(0, 0, bradius)
	local bfixture = bbody:createFixture{shape = bcircle,density = 0.7, restitution = 0.6, friction = 0.2, filter = {categoryBits = 2, maskBits = 1}}
	shotball:setAnchorPoint(0.5,0.5)
	bbody:setAngle(shotball:getRotation() * math.pi/180)
	shotball.body = bbody
	shotball.body.type = "ball"
	shotball:setPosition(400,100)	
 
	self.layer:addChild(shotball)
 
end
 
function game:onEnterFrame(event) 
	self.world:step(1/60, 10,8 )
 
	for i = 1, self:getNumChildren() do
		--get specific sprite
		local sprite = self:getChildAt(i)
		print(i)
		-- check if sprite HAS a body (ie, physical object reference we added)
		if sprite.body then
			--update position to match box2d world object's position
			--get physical body reference
			local body = sprite.body
			--get body coordinates
			local bodyX, bodyY = body:getPosition()
			--apply coordinates to sprite
			sprite:setPosition(bodyX, bodyY)
			--apply rotation to sprite
			sprite:setRotation(body:getAngle() * 180 / math.pi)
		end
	end
end
 
--removing event on exiting game
--just in case you're using gameManager
function game:onExitBegin()
  self:removeEventListener(Event.ENTER_FRAME, self.onEnterFrame, self)
end
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    Comments

    • zvardinzvardin Member
      Accepted Answer
      In your code, I don't think sprite has a body property.
      local sprite = self:getChildAt(i)
      This line is going to fetch the layer, but not the shotball object you added to the layer, which has a box2d body etc.
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    • plamenplamen Member
      Accepted Answer
      if i understand correct shotball is your image. It is declared as local and it is not accessible outside init function. This:
      local shotball = Bitmap.new(Texture.new("images/ball.png"))
      should be:
      self.shotball = Bitmap.new(Texture.new("images/ball.png"))
      You need to expose the body also with: self.body=bbody in "Init" function

      and then in "onEnterFrame" handler:
      you need self.shotball:setPosition(self.body:getPosition())
      self.shotball:setRotation(self.body:getRotation())

      The problem is that you assign bbody to shotball object and thus both have local scope inside "Init" function and are not exposed as subobjects of the class "game"

      https://www.facebook.com/Clouds0fSteel
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    • ar2rsawseenar2rsawseen Maintainer
      edited December 2012 Accepted Answer
      exactly as @zvardin and @plamen said.

      Easiest fix would be (provided that you add all physics bodies to the layer) is to change one line in you onEnterFrame method:
      for i = 1, self:getNumChildren() do
      to
      for i = 1, self.layer:getNumChildren() do
      http://appcodingeasy.com/Gideros-Mobile
      +1 -1Share on Facebook
    • mefistomefisto Member
      Ahhh ,my mistake :\"> at least it is forgivable when you are working on past 20 hours Thanks @zvardin , @plamen and @ar2saween for your answers.
      +1 -1Share on Facebook
    • zvardinzvardin Member
      Happens to all of us :) Glad it helped!
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