Attempt to index local 'button' (a nil value)

Getting Started Newbie Questions
#1

I’m walking through the following tutorial 

http://www.youtube.com/watch?v=Y5Oz72MO4JI

but for some reason i’m getting the error Attempt to index local 'button' (a nil value)

I’ve rechecked everything in my code, and it seams correct like in the video

the full error:

    ui.lua:130 Attempt to index local ‘button’ (a nil value)

    stack traceback:

    [C]:?

    

    ui.lua:130 in function ‘newButton’

code:

    -----------------------------------------------------------------------------------------

    –

    – main.lua

    –

    -----------------------------------------------------------------------------------------

    local ui = require(“ui”)

    local background = display.newImage(“background.jpg”)

    local gear = display.newImage(“gear.png”)

    local gear2 = display.newImage(“gear.png”)

    

    gear.x = display.stageWidth / 2 + 26

    gear.y = display.stageHeight / 2 - 50

    gear2.x = display.stageWidth * .63

    gear2.y = display.stageHeight * .60

    

    local rotateAmount = 1

    

    local function animate( event )

        gear.rotation = gear.rotation + rotateAmount

        gear2.rotation = gear2.rotation - rotateAmount

    end

    

    Runtime:addEventListener( “enterFrame”, animate )

    

    local buttonHandler = function( event )

        if event.phase == “release” then

            if event.id == “stop” then

                rotateAmount = 0

            elseif event.id == “+1” then

                rotateAmount = rotateAmount + 1

            elseif event.id == “-1” then

                rotateAmount = rotateAmount - 1

            elseif event.id == “reverse” then

                rotateAmount = rotateAmount * -1

            end

        end

    end

    

    local button1 = ui.newButton{

        default = “button.png”,

        over = “buttonOver.png”,

        onEvent = buttonHandler,

        text = “Stop”,

        id = “stop”,

        size = 12,

        emboss = true

    }

#2

I think that’s an old tutorial.  The “ui” library has been replaced by the “widget” library.  Check it out here: http://docs.coronalabs.com/api/library/widget/index.html.  In many cases you can probably just replace “ui” with “widget” and you’ll be fine, but you should consult the widget API documentation carefully, as some of the parameter names have changed (for example, default is now defaultFile, and text is now label).

  • Andrew
#3

You’re missing the ui.lua module in your project most likely. Don’t use that library, use widget instead for the button.

#4

worked thanks.

i had the ui.lua file.

#5

[lua]

local ui = require(“ui”)

local background = display.newImage(“book.jpg”)

local gear = display.newImage( “gear.png” )

local gear2 = display.newImage( “gear.png” )

gear.xScale = .5

gear.yScale = .5

gear2.xScale = .5

gear2.yScale = .5

gear.x = display.stageWidth / 4 + 25

gear.y = display.stageHeight / 2 - 50

gear2.x = gear.x + gear.stageWidth * .67

gear2.y = gear.y + gear.stageHeight * .67

gear2.rotation = 7

local rotateAmount = 1

local function animate( event )

    gear.rotation = gear.rotation + rotateAmount

    gear2.rotation = gear2.rotation - rotateAmount

end

Runtime:addEventListener( “enterFrame”, animate );

local buttonHandler = function( event )

    if event.phase == “release” then

        if event.id == “stop” then

            rotateAmount = 0

        elseif event.id == “+1” then

            rotateAmount = rotateAmount + 1

        elseif event.id == “-1” then

            rotateAmount = rotateAmount - 1

        elseif event.id == “reverse” then

            rotateAmount = rotateAmount * -1

        end

    end

end

local button1 = ui.newButton{

    default = “buttonGray.png”,

    over = “buttonGrayOver.png”,

    onEvent = buttonHandler,

    text = “Stop”,

    id = “stop”,

    size = 12,

    emboss = true

}

local button2 = ui.newButton{

    default = “buttonGray.png”,

    over = “buttonGrayOver.png”,

    onEvent = buttonHandler,

    text = “+1”,

    id = “+1”,

    size = 12,

    emboss = true

}

local button3 = ui.newButton{

    default = “buttonGray.png”,

    over = “buttonGrayOver.png”,

    onEvent = buttonHandler,

    text = “-1”,

    id = “-1”,

    size = 12,

    emboss = true

}

local button4 = ui.newButton{

    default = “buttonGray.png”,

    over = “buttonGrayOver.png”,

    onEvent = buttonHandler,

    text = “Reverse”,

    id = “reverse”,

    size = 12,

    emboss = true

}

button1.x = (display.stageWidth / 4 * 1) - display.stageWidth / 8; button1.y = 460

button2.x = (display.stageWidth / 4 * 2) - display.stageWidth / 8; button2.y = 460

button3.x = (display.stageWidth / 4 * 3) - display.stageWidth / 8; button3.y = 460

button4.x = (display.stageWidth / 4 * 4) - display.stageWidth / 8; button4.y = 460

[/lua]

#6

I think that’s an old tutorial.  The “ui” library has been replaced by the “widget” library.  Check it out here: http://docs.coronalabs.com/api/library/widget/index.html.  In many cases you can probably just replace “ui” with “widget” and you’ll be fine, but you should consult the widget API documentation carefully, as some of the parameter names have changed (for example, default is now defaultFile, and text is now label).

  • Andrew
#7

You’re missing the ui.lua module in your project most likely. Don’t use that library, use widget instead for the button.

#8

worked thanks.

i had the ui.lua file.

#9

[lua]

local ui = require(“ui”)

local background = display.newImage(“book.jpg”)

local gear = display.newImage( “gear.png” )

local gear2 = display.newImage( “gear.png” )

gear.xScale = .5

gear.yScale = .5

gear2.xScale = .5

gear2.yScale = .5

gear.x = display.stageWidth / 4 + 25

gear.y = display.stageHeight / 2 - 50

gear2.x = gear.x + gear.stageWidth * .67

gear2.y = gear.y + gear.stageHeight * .67

gear2.rotation = 7

local rotateAmount = 1

local function animate( event )

    gear.rotation = gear.rotation + rotateAmount

    gear2.rotation = gear2.rotation - rotateAmount

end

Runtime:addEventListener( “enterFrame”, animate );

local buttonHandler = function( event )

    if event.phase == “release” then

        if event.id == “stop” then

            rotateAmount = 0

        elseif event.id == “+1” then

            rotateAmount = rotateAmount + 1

        elseif event.id == “-1” then

            rotateAmount = rotateAmount - 1

        elseif event.id == “reverse” then

            rotateAmount = rotateAmount * -1

        end

    end

end

local button1 = ui.newButton{

    default = “buttonGray.png”,

    over = “buttonGrayOver.png”,

    onEvent = buttonHandler,

    text = “Stop”,

    id = “stop”,

    size = 12,

    emboss = true

}

local button2 = ui.newButton{

    default = “buttonGray.png”,

    over = “buttonGrayOver.png”,

    onEvent = buttonHandler,

    text = “+1”,

    id = “+1”,

    size = 12,

    emboss = true

}

local button3 = ui.newButton{

    default = “buttonGray.png”,

    over = “buttonGrayOver.png”,

    onEvent = buttonHandler,

    text = “-1”,

    id = “-1”,

    size = 12,

    emboss = true

}

local button4 = ui.newButton{

    default = “buttonGray.png”,

    over = “buttonGrayOver.png”,

    onEvent = buttonHandler,

    text = “Reverse”,

    id = “reverse”,

    size = 12,

    emboss = true

}

button1.x = (display.stageWidth / 4 * 1) - display.stageWidth / 8; button1.y = 460

button2.x = (display.stageWidth / 4 * 2) - display.stageWidth / 8; button2.y = 460

button3.x = (display.stageWidth / 4 * 3) - display.stageWidth / 8; button3.y = 460

button4.x = (display.stageWidth / 4 * 4) - display.stageWidth / 8; button4.y = 460

[/lua]