KEY_UP and KEY_DOWN listeners

MoKaLux · November 2020

I need your help please

I am a bit confused and I don't find the answer. I am trying to implement Event.KEY_DOWN and KEY_UP in a separate class but that doesn't work

1st class:

LevelX = Core.class(Sprite)
 
function LevelX:init()
	self.player = Player.new() -- calling 2nd class here
	self:addEventListener(Event.ENTER_FRAME, self.onEnterFrame, self)
end
 
function LevelX:onEnterFrame(e)
end

2nd class:

Player = Core.class(Sprite)
 
function Player:init()
	self.isleft, self.isright, self.isup, self.isdown = false, false, false, false
	self:addEventListener(Event.ENTER_FRAME, self.onEnterFrame, self)
	self:addEventListener(Event.KEY_DOWN, self.onKeyDown, self)
end
 
function Player:onEnterFrame(e)
	print("xxx") -- that works OK
end
 
function Player:onKeyDown(e)
	print("yyy") -- that does not work NOT OK
	if e.keyCode == KeyCode.I then self.isup = true end -- that does not work NOT OK
end

What am I doing wrong please? Is there a typo somewhere? I am sure I had it working before

MoKaLux · November 2020

EDIT: I found my error

LevelX = Core.class(Sprite)
 
function LevelX:init()
	self.player = Player.new() -- calling 2nd class here
	self:addChild(self.player) -- NOW EVERYTHING IS OK
	self:addEventListener(Event.ENTER_FRAME, self.onEnterFrame, self)
end
 
function LevelX:onEnterFrame(e)
end

We need to add it to stage for it to receive keyup and keydown events.

It is a bit inconsistent I think because enterframe event triggers without adding sprite to stage!

rrraptor · November 2020

You need to add sprite to a scene. So

stage:addChild(Player.new())

will do the job

MoKaLux · November 2020

MoKaLux said:
We need to add it to stage for it to receive keyup and keydown events.

thank you ~~antix~~ rrraptor, we posted at the same time

What do you think about the following?

MoKaLux said:
It is a bit inconsistent I think because enterframe event triggers without adding sprite to stage!

MoKaLux · November 2020

a bonus question:
Why do we have to add two times a bitmap to a sprite?
For example in my class player I do:

local bitmap = Bitmap.new(Texture.new("img.png"))
self:addChild(bitmap)

And I need to do the same in my game class:

local player = Player.new()
self:addChild(player)

Isn't it redundant to do two times addChild?

Sorry I am back to the basics

If I undestand this correctly the first addChild seems fair.
The second addChild (in the game class) is because we created the object player but it's up to me to add it to the stage or not. So by default an instance of player is created but not added to stage.

My opinion should be to add the instance automatically to the stage, my two cents

rrraptor · November 2020

MoKaLux said:
It is a bit inconsistent I think because enterframe event triggers without adding sprite to stage!

Idk for this one.

MoKaLux said:
a bonus question:
Why do we have to add two times a bitmap to a sprite?
For example in my class player I do:
local bitmap = Bitmap.new(Texture.new("img.png"))
self:addChild(bitmap)
And I need to do the same in my game class:
local player = Player.new()
self:addChild(player)
Isn't it redundant to do two times addChild?

Because this is 2 different objects? First is an image, second is your player controller.
If you want, you can move bitmap into player class, so it will look like:

Player = Core.class(Sprite)
function Player:init(texture)
	self.btm = Bitmap.new(texture)
	self:addChild(self.btm)
end
-- ...
 
local player = Player.new("gfx/player.png")
stage:addChild(player)

MoKaLux said:
My opinion should be to add the instance automatically to the stage, my two cents

If I have a SceneManager then I want my sprites to appear on a scene, but not on stage, because stage is a global sprite object that contains all other sprites (including scene manager) and cant be removed (but can be hidden

)

MoKaLux · November 2020

rrraptor said:
If you want, you can move bitmap into player class, so it will look like:...)

That's what I do in my code.

rrraptor said:
If I have a SceneManager then I want my sprites to appear on a scene, but not on stage

I meant ultimately the sprite is added to stage (sprite->scene->stage).

So those remain:
We need to add sprite to scene for it to receive keyup and keydown events.
It is a bit inconsistent because enterframe event triggers without adding sprite to scene.

Why do we have to add two times a bitmap to a sprite?
My opinion should be to add the instance automatically to the scene, my two cents

keszegh · November 2020

@MoKaLux , i don't agree with you.
the philosophy is that keys should behave like mouse events and for those it's quite natural that they are received only if the object is on the stage hierarchy.
on the other hand enterframe events are quite natural to affect objects that are not on the stage (e.g. a hidden object that nevertheless needs to be updated).

also i don't understand why you regard the bitmap as being added 'twice' to the stage, it is only added once to a parent and the parent is added to the stage. so only once it is assigned a parent (which is added to stage before or after, does not matter).

keszegh · November 2020

btw probably the best practice is to assign key events with stage itself.

MoKaLux · November 2020

thank you keszegh, yes now that totally makes sense

keszegh said:
btw probably the best practice is to assign key events with stage itself.

We control the player so I wanted to add the controls to the player class.

Thank you all for your insights.

Viva gideros

keszegh · November 2020

yes, also i agree that key events are less obvious (compared to mouse events) whether should have the need to the object be added to stage, both solutions can be argued for, but the current one is as good as any.

keszegh · November 2020

btw you can always add a dummy empty sprite to the stage 'belonging' to your player just to receive key etc. events.

antix · November 2020

@MoKaLux I created a little class to manage key presses, maybe it would be of some use?

https://github.com/Antix-Development/KeyManager

MoKaLux · December 2020

~~The problem I see with how gideros works is that I add the player to a sprite then the sprite gets added to the game class -> key event don't work~~

= NOT COOL because enterframe event works

	-- a player
	self.player1 = Player.new(self.world)
	self.tiled_level.camera:addChild(self.player1)

PS: antix, sorry did not reply earlier but I would like to make the key events belong to my player class first.

EDIT: see post below

hgy29 · December 2020

@MoKaLux, see http://forum.giderosmobile.com/discussion/comment/64539/#Comment_64539

MoKaLux · December 2020

sorry hgy29 but this still bugs me that enter frame event works and not key events

MoKaLux · December 2020

btw you can always add a dummy empty sprite to the stage 'belonging' to your player just to receive key etc. events.

Ok, I think I am going this way instead (the closest to what I would want so far):

LevelX = Core.class(Sprite)
 
function LevelX:init()
	-- BG
	application:setBackgroundColor(0x0)
	...
	-- PLAYER KEYS LISTENERS
	self:addEventListener(Event.KEY_DOWN, self.player1.onKeyDown, self.player1)
	self:addEventListener(Event.KEY_UP, self.player1.onKeyUp, self.player1)
end

Thank you all for your insights

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