removeChild error on exiting and entering scene

somezombiegm · March 2014

Sorry for the long question, I appretiate you reading this.

I have a general problem which involves my game objects and the menu bar which is on top of the screen. I have some "bullet" bitmaps which can fly in every direction, but since every time the user shoots I add a new child to the stage, the bullets end on top of the menu, which I dont want.

So to fix this, on my update function (which is called with the Event.ENTER_FRAME event) every time I add a new bullet as a child, I remove the menu and immediately add it as a child again. However the problem with this is that if i go back to the start scene (yeah I'm using ar2rs Game Template project) and then return to my game it keeps working, but if I change scene and return to my game scene a 3rd time, the "remove and then add" solution throws an error; on my remove line the error says: "The suplied sprite must be a child of the caller". I remove and add the menu like a thousand times before, I dont know why when I enter the scene for the third time it throws me this error, please help.

The menu bitmap IS being added as a child, but acording to the error it isnt.

I can't show any code cause it's too large, and when I reduce it for testing it with only two bitmaps, the error doesn't happen any more :S.

It would be good to know why this happens so I could fix it, however, another way around it would be welcome. Like for example a bitmap function that puts an image on top or behind. That would be cool actually.

Anyway, that was the question...

OZApps · March 2014

@somezombiegame,
have you looked at addChildAt?

A simple way would be to have 2 layers, the game layer and the menu layer, keep the menu layer onTop of the game layer and keep adding your bullets to the game layer, that way it will be current in the game layer and also below the menu layer.

somezombiegm · March 2014

Havent heard of addChildAt or layers either, let me read something about it and see how to implement it.

ar2rsawseen · March 2014

@somezombiegm
With layers you can do something like that:

Scene = Core.class(Sprite)
 
function Scene:init()
    self.bulletLayer = Sprite.new()
    self:addChild(self.bulletLayer)
 
    self.menu = Sprite.new()
    self:addChild(self.menu)
end
 
function Scene:addBullet(bullet)
    -- now bullet will be added to bullet layer
    -- and will always be under menu
    -- because it was added to the scene before menu
    self.bulletLayer:addChild(bullet)
end

SinisterSoft · March 2014

Do something like bullets=Sprite.new(), then stage:addChild(bullets), than add your bullets as child sprites to bullets.

You can then loop though bullets and process them as you want (technically it might be faster to process them in a table then move specific table data to the correct bullet sprite though - this depends on what you are doing).

Then add a new sprite called ui, eg ui=Sprite.new(), stage:addChild(ui). And then add your bits for your panel.

Because ui was added to stage AFTER bulllets then it will normally always be on top of bullets on screen. You can add and remove sprites to bullets and they will always be below ui (unless you change the order of things on the stage).

SinisterSoft · March 2014

Argh... @ar2rsawseen - faster than me again!

whidbey · March 2014

hi all,
could the removeChild will auto release the sub group objects?
regards

ar2rsawseen · March 2014

@whidbey yes

http://giderosmobile.com/forum/discussion/comment/9441#Comment_9441

whidbey · March 2014

thanks #@ar2rsawseen

somezombiegm · March 2014

Thanks a lot for your help. I did used Sprites on a tutorial but I didn't knew you can implement them as layers. Having all my game elements on a Sprite and all my menu elements on another works fine. I just have to put stage:addChild(gameLayer) before stage:addChild(menuLayer). And all the corresponding elements to the corresponding layers as all of you said.

@whidbey yeah, if I put stage:removeChild(gameLayer) all of the elements added to that layer will be gone.

whidbey · March 2014

@somezombiegm ,ok, and do you have a menu classes? would you share with me?thank you

somezombiegm · March 2014

@whidbey Menu Classes? I'm using ar2rs Game Template which has a scene manager.

http://giderosmobile.com/forum/discussion/480/gideros-game-template/p1

Not sure if that's what you want.

OZApps · March 2014

Just one small point of concern, I am not sure who had started that thread. While removeChild will remove the children, there could be instances where the listeners still remain and in some bizarre cases cause funny things to happen. So while you can rely on the removeChild to remove all sub groups, etc make sure that you remove the eventListeners (if any) on the sub groups and grandchildren.

Paulo777 · March 2018

Hello!
I1m having a problem that: The supplied Sprite must be a child of the caller. I still didn't understand the structure of that 'cause every time is a different behaviour. Doesn't makes sense we add a sprite and not be able to remove that gives this error... doesn't makes any sense... I'll show an example

local sprite = Sprite.new()
 
self:addChild(sprite) -- works
 
self:removeChild(sprite) --ERROR The supplied Sprite must be a child of the caller

Can anybody explain this?

totebo · March 2018

So long as "sprite" is still in scope, that code looks fine. Although I tend to use sprite:removeFromParent() instead, because I'm lazy.

Paulo777 · March 2018

@totebo haha this also have worked for me! But I mean in my case it gives me error because in my "sprite" I have 3 movieclips, maybe, I suppose to... Still in this scenario, removeFromParent seems to work but I noticed it remain in memory... Suppose that I want not my sprite to be in the stage, or child sprite, what Can I do to "destroy" it definetly?

Apollo14 · March 2018

collectgarbage() maybe?

totebo · March 2018

what Can I do to "destroy" it

Once there are no references to a sprite it is garbage collected automatically. So just set all the variables containing a reference to it to nil and you should be good.

You can control when to garbage collect by using collectgarbage() like @apollo14 suggests, but this will only garbage collect sprites with no references. So long as there is one or more references to the sprite, it will never be garbage collected.

Howdy, Stranger!

Categories

In this Discussion

Top Posters

removeChild error on exiting and entering scene

Comments

Howdy, Stranger!

Quick Links

Categories

In this Discussion

Top Posters

removeChild error on exiting and entering scene

Comments