Super Basic Question

joethemojo

I'm very new to Gideros and I have looked around for this answer but I'm getting a little frustrated.

I'm starting off very basic.

Id like to move a sprite with the arrow keys on the keyboard.
and after you release to key the sprite still moves a little in that direction.

I have no idea how to do this.
Ive looked in the reference and I think I somehow merge these 2 codes?

function onMouseDown(event)
print(event.x, event.y) <--- but a translate function?
end
mysprite:addEventListener(Event.MOUSE_DOWN, onMouseDown)

with

stage:addEventListener(Event.KEY_DOWN, function(event)
if event.keyCode == KeyCode.BACK then
application:exit() <----- with translate function?
end
end)

Then I think another event for when I let go of the key?


If anyone could help me Id greatly appreciate this.

Joe

eezing

Here's an example of how act upon key up/down. As far as moving a sprite... that would be separate functionality.

-- The sprite that will listen for key up/down events   local sprite = Sprite.new() stage:addChild(sprite)       -- Assign Up arrow as our move key   local moveKey = KeyCode.UP         -- Our function when key is pressed   local function move()   print("begin moving") end   -- Our funcion when key is released   local function stop()   print("begin stop moving") end         -- Our listener function for when key is Down   local function onKeyDown(event)   if event.keyCode == moveKey then   move()   end end   -- Our listener function for when key goes Up   local function onKeyUp(event)   if event.keyCode == moveKey then   stop()   end end       -- Our event listeners to start the actions   sprite:addEventListener(Event.KEY_DOWN, onKeyDown, event) sprite:addEventListener(Event.KEY_UP, onKeyUp, event)

joethemojo

Thank you!!!

eezing

For moving sprites...

There's probably a bunch of examples in these forums... but there are basically two ways.

The first way is to use box2d if you require sprites to interact and collide with each other. Box2d at first can be a bit overwhelming, but extremely valuable once you get the hang of it.

The second is something like this (using my example above):

-- The sprite that will listen for key up/down events   local sprite = Sprite.new() stage:addChild(sprite)     -- Define attributes of move action for sprite   local fps = 60 local speed = 200 local drag = 0.05 local stopAtSpeed = 5     -- The moving function that will run on every frame   local sx = stopAtSpeed * (1 / fps) local dx, dsx, x = 0, 0, 0   local function moving()   -- get next amount to move dx = dx * (1 - dsx)   -- new position = last position + next amount to move x = x + dx sprite:setX(x)   -- if next amount to move is less than this, kill listener if math.abs(dx) < sx then   if sprite:hasEventListener(Event.ENTER_FRAME) then sprite:removeEventListener(Event.ENTER_FRAME, moving) end end   print(x, dx) end   --------------------------------------------------   -- Assign Up arrow as our move key   local moveKey = KeyCode.UP       -- Our function when key is pressed   local function move()   -- No drag when moving dsx = 0   -- Set our amount to move to full dx = speed * (1 / fps)   -- Get starting position x = sprite:getX()   -- Start listening at every frame if not sprite:hasEventListener(Event.ENTER_FRAME) then sprite:addEventListener(Event.ENTER_FRAME, moving) end end   -- Our funcion when key is released   local function stop()   -- Apply drag dsx = drag end         -- Our listener function for when key is Down   local function onKeyDown(event)   if event.keyCode == moveKey then   move()   end end   -- Our listener function for when key goes Up   local function onKeyUp(event)   if event.keyCode == moveKey then   stop()   end end       -- Our event listeners to start the actions   sprite:addEventListener(Event.KEY_DOWN, onKeyDown, event) sprite:addEventListener(Event.KEY_UP, onKeyUp, event)

OZApps

@joethemojo,
you are aware that not all mobile devices would have and respond to the arrow keys.

john26

A KEY_DOWN event only fires when the user first presses the key down. When the user releases the key, a KEY_UP event occurs. But in between there are no events. It's important to realize the system will not constantly send you a series of KEY_DOWN events. So you need a boolean variable eg keypressed which you set to true when you get KEY_DOWN and false when you get KEY_UP. Then, you use an ENTER_FRAME listener to update the sprite position, eg

if keypressed then sprite:setX(sprite:getX()+1) end.

Same deal for MOUSE_DOWN, MOUSE_UP.