I have this error,
“Attempt to perform arithmetic on field ‘x’ (a nil value) stack traceback:”
if someone can help me…
function redraw ()
Trail = display.newCircle( myCircle.x + trailprops.x, myCircle.y + trailprops.y, trailprops.r)
Trail:setFillColor (255, 0, 0)
myCircle:toFront( )
sceneGroup:insert(Trail)
end
Runtime:addEventListener( “enterFrame”, redraw )
i also have problems on arthimetic value im new to lua and i cant seem to understand how simple addition works on values
btnCounter = txtNumber
txtNumber = btnCounter + 1
print( btnCounter )
thats the code but it show arithmetic error. can someone explain why and how to fix that? thanks
Hi ri_cruz,
Are you adding the enterFrame listener before the myCircle and trailprops objects have been created? If either of them are set to nil when the program reaches your enterFrame listener, it will fail. Try the following:
function redraw () --Only execute the following if the myCircle and trailprops objects exist... if (myCircle) and (trailprops) then Trail = display.newCircle( myCircle.x + trailprops.x, myCircle.y + trailprops.y, trailprops.r) Trail:setFillColor (255, 0, 0) myCircle:toFront( ) sceneGroup:insert(Trail) end end
If the above works, then it means you need to call Runtime:addEventListener later in your program.
Hi guiller,
I think your problem may be similar. If txtNumber hasn’t been set to anything before you call your code, then it will fail.
--If txtNumber is nil at this point, btn Counter will be nil too. btnCounter = txtNumber --Your code will fail, because you can't add 1 to nil. txtNumber = btnCounter + 1
An easy debug test would be:
if (not txtNumber) then --If the program counter gets here, txtNumber is set to nil (ie. hasn't been set yet) print("txtNumber hasn't been set yet!") else --If the program counter gets here, txtNumber has something in it. btnCounter = txtNumber txtNumber = btnCounter + 1 print( btnCounter ) endYes, it works, but the trail doen’t show
Hi again,
That means either myCircle or trailprops doesn’t exist when the redraw function is called. You probably need to call Runtime:addEventListener( “enterFrame”, redraw ) later in your program.
Hi happy
I try call runtime later and the error continue appearing.
If you wanna see my code, it’s here:
local composer = require( “composer” )
local scene = composer.newScene()
local widget = require (“widget”)
local function buttonHit(event)
composer.gotoScene( event.target.destination )
return true
end
– “scene:create()”
function scene:create( event )
local sceneGroup = self.view
local background = display.newImage( “campo-futebol.jpg”)
sceneGroup:insert(background)
–backButton
local backBtn = display.newText(“Back”, 0, 0, “Helvetica”, 38)
backBtn.x= 640
backBtn.y= 970
backBtn.destination = “menu”
backBtn:addEventListener(“tap”, buttonHit)
composer.removeScene(true)
sceneGroup:insert(backBtn)
– Limites do ecrã
local borderTop = display.newRect( 0, 0, 707, 1 )
borderTop:setFillColor( 0, 0, 0, 0) – make invisible
physics.addBody( borderTop, “static”, borderBodyElement )
sceneGroup:insert(borderTop)
local borderBottom = display.newRect( 0, 1000, 707, 1 )
borderBottom:setFillColor( 0, 0, 0, 0) – make invisible
physics.addBody( borderBottom, “static”, borderBodyElement )
sceneGroup:insert(borderBottom)
local borderLeft = display.newRect( 0, 1, 1, 1000 )
borderLeft:setFillColor( 0, 0, 0, 0) – make invisible
physics.addBody( borderLeft, “static”, borderBodyElement )
sceneGroup:insert(borderLeft)
local borderRight = display.newRect( 707, 1, 1, 1000 )
borderRight:setFillColor( 0, 0, 0, 0) – make invisible
physics.addBody( borderRight, “static”, borderBodyElement )
sceneGroup:insert(borderRight)
– Initialize the scene here.
– Example: add display objects to “sceneGroup”, add touch listeners, etc.
end
– “scene:show()”
function scene:show( event )
local sceneGroup = self.view
local phase = event.phase
if ( phase == “will” ) then
– Called when the scene is still off screen (but is about to come on screen).
local myCircle = display.newCircle(40, 40, 30)
physics.addBody (myCircle, “dynamic”, {density=1.0, friction=0.5, bounce=0.0 } )
myCircle:setFillColor ( 255, 0, 0)
myCircle.x = 580
myCircle.y = 435
sceneGroup:insert(myCircle)
local function circleTouch(event)
local touchedObject = event.target
–Mover circuloVermelho
if event.phase == “began” then
touchedObject.previousX = touchedObject.x
touchedObject.previousY = touchedObject.y
elseif event.phase == “moved” then
touchedObject.x = (event.x - event.xStart) + touchedObject.previousX
touchedObject.y = (event.y - event.yStart) + touchedObject.previousY
end
return true
end
myCircle:addEventListener( “touch”, circleTouch)
local trailprops = {x= 0, y = 0,r = 5} – r= tamanho do circulo do rasto
function redraw () – Desenha o rasto
Trail = display.newCircle( myCircle.x + trailprops.x, myCircle.y + trailprops.y, trailprops.r)
Trail:setFillColor (255, 0, 0)
myCircle:toFront( )
sceneGroup:insert(Trail)
end
Runtime:addEventListener( “enterFrame”, redraw )
elseif ( phase == “did” ) then
– Called when the scene is now on screen.
– Insert code here to make the scene come alive.
– Example: start timers, begin animation, play audio, etc.
end
end
– “scene:hide()”
function scene:hide( event )
local sceneGroup = self.view
local phase = event.phase
if ( phase == “will” ) then
– Called when the scene is on screen (but is about to go off screen).
– Insert code here to “pause” the scene.
– Example: stop timers, stop animation, stop audio, etc.
elseif ( phase == “did” ) then
– Called immediately after scene goes off screen.
end
end
– “scene:destroy()”
function scene:destroy( event )
local sceneGroup = self.view
– Called prior to the removal of scene’s view (“sceneGroup”).
– Insert code here to clean up the scene.
– Example: remove display objects, save state, etc.
end
– Listener setup
scene:addEventListener( “create”, scene )
scene:addEventListener( “show”, scene )
scene:addEventListener( “hide”, scene )
scene:addEventListener( “destroy”, scene )
return scene
Hi again,
Your code runs fine when I tried it on my machine using the latest daily build 
Maybe this is scoping problem in an earlier build of Corona?
I have this one “Build 2015.2632” and what do you have?
The error starts when I start on the menu scene and go to that one, when I want to come back to the menu scene again, it give me that error
i also have problems on arthimetic value im new to lua and i cant seem to understand how simple addition works on values
btnCounter = txtNumber
txtNumber = btnCounter + 1
print( btnCounter )
thats the code but it show arithmetic error. can someone explain why and how to fix that? thanks
Hi ri_cruz,
Are you adding the enterFrame listener before the myCircle and trailprops objects have been created? If either of them are set to nil when the program reaches your enterFrame listener, it will fail. Try the following:
function redraw () --Only execute the following if the myCircle and trailprops objects exist... if (myCircle) and (trailprops) then Trail = display.newCircle( myCircle.x + trailprops.x, myCircle.y + trailprops.y, trailprops.r) Trail:setFillColor (255, 0, 0) myCircle:toFront( ) sceneGroup:insert(Trail) end end
If the above works, then it means you need to call Runtime:addEventListener later in your program.
Hi guiller,
I think your problem may be similar. If txtNumber hasn’t been set to anything before you call your code, then it will fail.
--If txtNumber is nil at this point, btn Counter will be nil too. btnCounter = txtNumber --Your code will fail, because you can't add 1 to nil. txtNumber = btnCounter + 1
An easy debug test would be:
if (not txtNumber) then --If the program counter gets here, txtNumber is set to nil (ie. hasn't been set yet) print("txtNumber hasn't been set yet!") else --If the program counter gets here, txtNumber has something in it. btnCounter = txtNumber txtNumber = btnCounter + 1 print( btnCounter ) endYes, it works, but the trail doen’t show
Hi again,
That means either myCircle or trailprops doesn’t exist when the redraw function is called. You probably need to call Runtime:addEventListener( “enterFrame”, redraw ) later in your program.
Hi happy
I try call runtime later and the error continue appearing.
If you wanna see my code, it’s here:
local composer = require( “composer” )
local scene = composer.newScene()
local widget = require (“widget”)
local function buttonHit(event)
composer.gotoScene( event.target.destination )
return true
end
– “scene:create()”
function scene:create( event )
local sceneGroup = self.view
local background = display.newImage( “campo-futebol.jpg”)
sceneGroup:insert(background)
–backButton
local backBtn = display.newText(“Back”, 0, 0, “Helvetica”, 38)
backBtn.x= 640
backBtn.y= 970
backBtn.destination = “menu”
backBtn:addEventListener(“tap”, buttonHit)
composer.removeScene(true)
sceneGroup:insert(backBtn)
– Limites do ecrã
local borderTop = display.newRect( 0, 0, 707, 1 )
borderTop:setFillColor( 0, 0, 0, 0) – make invisible
physics.addBody( borderTop, “static”, borderBodyElement )
sceneGroup:insert(borderTop)
local borderBottom = display.newRect( 0, 1000, 707, 1 )
borderBottom:setFillColor( 0, 0, 0, 0) – make invisible
physics.addBody( borderBottom, “static”, borderBodyElement )
sceneGroup:insert(borderBottom)
local borderLeft = display.newRect( 0, 1, 1, 1000 )
borderLeft:setFillColor( 0, 0, 0, 0) – make invisible
physics.addBody( borderLeft, “static”, borderBodyElement )
sceneGroup:insert(borderLeft)
local borderRight = display.newRect( 707, 1, 1, 1000 )
borderRight:setFillColor( 0, 0, 0, 0) – make invisible
physics.addBody( borderRight, “static”, borderBodyElement )
sceneGroup:insert(borderRight)
– Initialize the scene here.
– Example: add display objects to “sceneGroup”, add touch listeners, etc.
end
– “scene:show()”
function scene:show( event )
local sceneGroup = self.view
local phase = event.phase
if ( phase == “will” ) then
– Called when the scene is still off screen (but is about to come on screen).
local myCircle = display.newCircle(40, 40, 30)
physics.addBody (myCircle, “dynamic”, {density=1.0, friction=0.5, bounce=0.0 } )
myCircle:setFillColor ( 255, 0, 0)
myCircle.x = 580
myCircle.y = 435
sceneGroup:insert(myCircle)
local function circleTouch(event)
local touchedObject = event.target
–Mover circuloVermelho
if event.phase == “began” then
touchedObject.previousX = touchedObject.x
touchedObject.previousY = touchedObject.y
elseif event.phase == “moved” then
touchedObject.x = (event.x - event.xStart) + touchedObject.previousX
touchedObject.y = (event.y - event.yStart) + touchedObject.previousY
end
return true
end
myCircle:addEventListener( “touch”, circleTouch)
local trailprops = {x= 0, y = 0,r = 5} – r= tamanho do circulo do rasto
function redraw () – Desenha o rasto
Trail = display.newCircle( myCircle.x + trailprops.x, myCircle.y + trailprops.y, trailprops.r)
Trail:setFillColor (255, 0, 0)
myCircle:toFront( )
sceneGroup:insert(Trail)
end
Runtime:addEventListener( “enterFrame”, redraw )
elseif ( phase == “did” ) then
– Called when the scene is now on screen.
– Insert code here to make the scene come alive.
– Example: start timers, begin animation, play audio, etc.
end
end
– “scene:hide()”
function scene:hide( event )
local sceneGroup = self.view
local phase = event.phase
if ( phase == “will” ) then
– Called when the scene is on screen (but is about to go off screen).
– Insert code here to “pause” the scene.
– Example: stop timers, stop animation, stop audio, etc.
elseif ( phase == “did” ) then
– Called immediately after scene goes off screen.
end
end
– “scene:destroy()”
function scene:destroy( event )
local sceneGroup = self.view
– Called prior to the removal of scene’s view (“sceneGroup”).
– Insert code here to clean up the scene.
– Example: remove display objects, save state, etc.
end
– Listener setup
scene:addEventListener( “create”, scene )
scene:addEventListener( “show”, scene )
scene:addEventListener( “hide”, scene )
scene:addEventListener( “destroy”, scene )
return scene
Hi again,
Your code runs fine when I tried it on my machine using the latest daily build
Maybe this is scoping problem in an earlier build of Corona?
I have this one “Build 2015.2632” and what do you have?
The error starts when I start on the menu scene and go to that one, when I want to come back to the menu scene again, it give me that error