if then on Runtime:addEventListener("enterFrame"

Getting Started Newbie Questions
#1

Hi, I have this enterFrame event listener:

 Runtime:removeEventListener(“enterFrame”, updateScore )   

Calling this function.

local function updateScore()
    if  gameActive then
    score = score + 5
    scoreTxt.text = "Score: " … score
    scoreTxt:setReferencePoint(display.cl);
    scoreTxt.x = 5
   end
end

Basically it just updates the score all the time if gameActive is true. I’m just wondering, is it a waste of processing time when the game is paused (gameActive=false) that the EventListener still calls the function? It calls it but doesn’t do anything if gameActive=false, so was wondering if there is another way to do this? Or is this how it should work?

Thanks,

Mark

#2

I’m assuming the issue is that your function isn’t being called, because you have removeEventListener instead of addEventListener.

#3

Hi, sorry I posted the wrong line.

It should be this:

  Runtime:addEventListener(“enterFrame”, updateScore )

#4

Can you give a bit more info on your code? What is the gameActive value? Normally an if/then statement looks more like this:

if gameActive == true then

Also, unless you have another function removing your scoreTxt.text object, you’re going to get overlapping objects.

#5

Thats about all the code I have for this.

I thought  ‘if  gameActive then’ was equivalent to if gameActive == true then 

Is that wrong then?

Is that creating a new text object everytime then? Sorry very new to this.

#6

I do have a local reference at the top of the file.

local score = 0
local scoreTxt

#7

You are correct, but I wasn’t sure if that was being defined by gameActive. I have numerical values qualifying my if/then statements.

You might want it to look more like this:

local scoreTxt = display.newText("",0,0,nativeFont, 8) local score = 0 local function updateScore() if gameActive == true then print("SCORE UPDATING") score = score + 5 scoreTxt.text = ("Score: " .. score) scoreTxt:setReferencePoint(display.cl); scoreTxt.x = 5 end end Runtime:addEventListener("enterFrame", updateScore)

Correct, it would create a new text object every time. Can you post a bit more of your code to evaluate?

#8

This is most of the code. The eventlisteners are invoked when the game starts.

local function updateScore(num)
    if  gameActive then
    score = score + num
    scoreTxt.text = "Score: " … score
    scoreTxt:setReferencePoint(display.cl);
    scoreTxt.x = 5

   end
   
end

local function updateDistance(num)
    if  gameActive then
    distanceToTravel = distanceToTravel - speed *2
    distanceToTravelTxt.text = "Distance to Travel: " … distanceToTravel
    distanceToTravelTxt:setReferencePoint(display.cl);
    distanceToTravelTxt.x = 5
    
     updateScore(speed)
   end
   
end

 local function pauseGame(event)

      if gameActive  then
          gameActive=false
          btnPause:setFrame( 1 )
       
      else
         
          gameActive=true
          btnPause:setFrame( 2 )
      
              
      end      
end  
 

function gameListeners(event)
    
    
    if event == “add” then
     
 
        Runtime:addEventListener(“accelerometer” , movement )         
        balloon:addEventListener(“touch” , increaseSpeed )
        Runtime:addEventListener(“enterFrame”, updateDistance )
        btnPause:addEventListener(“tap”, pauseGame)
       
    elseif event == “remove” then
        
        Runtime:removeEventListener(“accelerometer” , movement )
        balloon:removeEventListener(“touch” , increaseSpeed )
        Runtime:removeEventListener(“enterFrame”, updateDistance )     
        btnPause:removeEventListener(“tap”, pauseGame)
         
    end
end

Thanks for looking.

Mark

#9

is the speed variable defined elsewhere in the code?

#10

Yes sorry. At the top of the file

local score = 0
local scoreTxt
local speed = 8

I also have a hud function thats invoked before the listeners:

local hud = function()
      utils:log(“play.lua”, “hud()”);
      
       – init score    
           scoreTxt = display.newText(“Score: 0”, 5, 0, “Helvetica”, 14)
           scoreTxt:setTextColor(0, 0, 0, 150)   

           gameGroup:insert(scoreTxt)  

              – init  distance
           distanceToTravelTxt = display.newText("Distance to Travel: ", 5, 0, “Helvetica”, 14)
           distanceToTravelTxt:setTextColor(0, 0, 0, 150)  
         

           distanceToTravelTxt.y = screenBottom - 12
           gameGroup:insert(distanceToTravelTxt)  
           
end

#11

Am i duplicating object then with this?

Thanks.

#12

I’m not that familiar with the “remove” and “add” events you’ve used in your gamelisteners function, nor do I see where the gamelisteners function is being invoked. Was that also left off?

#13

Sorry its quite a big file.

This is what invokes it:

 local function gameStart()
      
        hud()
        initPause()
        initButtons()    
            
    end
    gameStart()  
    gameListeners(“add”)

gameListeners(“remove”) is used in the exit scene.

Thanks,

Mark

      

#14

You paste parts of the code which are dependent. If you can it would be better to post whole file (if not longer than tens of lines)

#15

It is certainly possible that I don’t know enough about lua syntax to help you any further, so keep that in mind when I make my suggestions:

I don’t believe an (event) function will fire unless listening to one of the properties associated with it. Maybe you can have and event function with a property of just “event == ‘add’”, but I haven’t found it.

You might be better served by creating separate add and remove functions for your Runtime listeners. It might be a bit more intuitive to make something like this:

function gameListenersON() Runtime:addEventListener("accelerometer" , movement ) balloon:addEventListener("touch" , increaseSpeed ) Runtime:addEventListener("enterFrame", updateDistance ) btnPause:addEventListener("tap", pauseGame) end function gameListenersOFF() Runtime:removeEventListener("accelerometer" , movement ) balloon:removeEventListener("touch" , increaseSpeed ) Runtime:removeEventListener("enterFrame", updateDistance ) btnPause:removeEventListener("tap", pauseGame) end

And then you can just call each when necessary. Again, I’m no Lua expert but this might be the best way to start.

#16

ok thanks. Going back to my original question then

Maybe all I need to do is to stop the listener below when gameActive == false. As this only needs to run when gameActive is true.
 

Runtime:removeEventListener(“enterFrame”, updateScore )   

Thanks for your help.

Mark

#17

It looks like updateScore is only being called in the updateDistance Runtime function, so if you remove updateDistance, it should remove updateScore.

#18

Oh yes i see that now. Thanks for helping.

Regards,

Mark

#19

Quick postscript to this that I didn’t notice earlier…

You don’t need to explicitly remove touch/tap functions that are associated with objects, such as 

balloon:removeEventListener("touch" , increaseSpeed )

Because if you are removing the balloon object at the end of the level/game, it will also remove the associated listeners. That should make things a bit more simple as well.

#20

Brilliant, thanks for that. I didn’t know that. I just need to check I’m removing the object! I’ve only posted a few times so apologies if I caused you an headache.