onEnterFrame execution order?

dwilson08

Hey guys,

I'm just starting to learn Gideros and I'm trying to make a fairly simple overhead racing/obstacle-avoid game. Currently, I'm having some weird issues with the onEnterFrame event not working like I expect. Right now it seems the order that my sprites run their onEnterFrame function seems to be somewhat random. Unfortunately for me, if those functions aren't run in particular order I get weird seams in my road tiles (from speed changes). Here's are some relevant snippets to describe my code.

Game.lua

... function game:init()   local roads = Sprite.new()   for i=0, 3 do local road = Road.new() road:setPosition(0, i*road:getHeight()) roads:addChild(road) end   self:addChild(roads)   local smPothole = Pothole.new("assets/pothole-s.png", small) self:addChild(smPothole) ...

road.lua

Road = Core.class(Sprite)   function Road:init() local bitmap = Bitmap.new(Texture.new("assets/roadTile.png")) self:addChild(bitmap) self:addEventListener(Event.ENTER_FRAME, self.onEnterFrame, self) end     function Road:onEnterFrame(event) local x, y = self:getPosition() local tileHeight = self:getHeight()   --[[Checks if tile is off the canvas and moves it to the top. Otherwise, move road tile down slightly to give illusion of car moving.]]   if y >= tileHeight*3 then local overshoot = y - tileHeight*3 self:setY(-tileHeight + overshoot + speed) else self:setY(y + speed) end end

pothole.lua

Pothole = Core.class(Sprite)   function Pothole:init(texture, size) --initialize pothole with texture passed as argument local bitmap = Bitmap.new(Texture.new(texture)) self.size = size self:addChild(bitmap) self:setPosition(120, 955) self:addEventListener(Event.ENTER_FRAME, self.onEnterFrame, self) end   function Pothole:onEnterFrame(event)   local x, y = self:getPosition()   -- moves pothole down screen with road, moves to top if off canvas. if y >= 954 then self:setY(math.random(-950,-50)) self:setX(math.random(70,330)) else self:setY(y + speed) end   -- hit collision with car. See init.lua if car:collision(self) then if speed > minSpeed then speed = speed - 0.2 speedometerNeedle:setRotation(speedometerNeedle:getRotation()-4.8) end end end

The problem is that if the pothole enterframe function is not run last, it changes the speed variable which makes the road tiles not line up properly (since it uses the speed variable to change position). I added a few print functions in that my code to figure out what order the functions were firing... and oddly enough it's different every time I reload in the player. (Are they all firing simultaneously and it's just my processor that's changing the order?)

What can I change so that all the road sprites run their onEnterFrame functions before the pothole sprites do?

Anyways, I'm just stumbling my way through this since I don't have a lot of programming experience. The code is probably pretty hackish, I'd love to hear how I can improve it.

Thanks in advance!

techdojo

The order (I suspect) is probably determined by the order the items are stored in their respective tables.

However what I would advise is to NOT have separate EnterFrame listeners but to assign a single EnterFrame listener to a master "control" object, it's then the job of this object to run the game. What you do then is call each objects EnterFrame (I prefer to rename it update) function in the order YOU specify - usually in a for loop or something like that.

If you take the same approach and have a single touch listener function as well, it might also make your life a LOT easier as well.

Hope this helps

joelghill

Yeah, I designed a similar game, and I had separate onEnterFrame listeners for different objects as well (something I probably won't do again.)

You could try a few things. I have no idea id they will work. First, rather that having the onEnterFrame listener for each road instance determine position, you could use the game onFrameListener to change the position of the roads sprite that you seem to have them stored in.

Or, do the same thing only move each road object within the roads sprite under a single onEnterFrame even in the main game script. (which is I think what I did with my game.... but I can't remember. Something like that)

@techdojo was probably right, using separate onEnterFrame instances will probably cause headaches for stuff like this.

dwilson08

@techdojo: Yup, had to do some rewriting but that seems like the solution that worked. I had separate listeners just to make my code a bit more mentally manageable but putting everything into one update function wasn't much harder. Now having separate classes seems pretty unnecessary. Thanks for your answer.

@joel: I think I stole the concept from your early source code . I ended up adding the roadtiles and potholes as children to sprites then looping through the children via indices in the main update function (called on onEnterFrame) to move them. Seems to work pretty good.