How can I access a lua file with a tab bar? - lua

Question

I am having an error when trying to access a file with a tab bar constructed within it. Does anyone know what I am doing wrong. Corona SDK tells me my error is in the section of code where I actually create the tab bar, not the buttons. Thanks
Below is my code for the MainPage.lua scene in which the tab bar is created.
local tabBar = nil
function scene: create (event)
local group = scene.view
local tabButtons =
{
{
width = 20,
height = 32,
defaultFile = "assets/home.png",
overFile = "assets/PressHome.png",
label = "Home",
font = tabLabelFont,
size = tabLabelFontSize,
onPress = function() composer.gotoScene( "Home" ); end,
},
{
width = 20,
height = 32,
defaultFile = "assets/Explore.png",
overFile = "assets/Explore.png",
label = "Explore",
font = tabLabelFont,
size = tabLabelFontSize,
onPress = function() composer.gotoScene( "Explore" ); end,
},
{
width = 20,
height = 32,
defaultFile = "assets/Post.png",
overFile = "assets/Post.png",
label = "Post",
font = tabLabelFont,
size = tabLabelFontSize,
onPress = function() composer.gotoScene( "Post" ); end,
},
{
width = 20,
height = 32,
defaultFile = "assets/Notification.png",
overFile = "assets/Notification.png",
label = "Notification",
font = tabLabelFont,
size = tabLabelFontSize,
onPress = function() composer.gotoScene( "Notification" ); end,
},
{
width = 20,
height = 32,
defaultFile = "assets/Profile.png",
overFile = "assets/Profile.png",
label = "Profile",
font = tabLabelFont,
size = tabLabelFontSize,
onPress = function() composer.gotoScene( "Profile" ); end,
}
}
-- Create a tab-bar and place it at the bottom of the screen
tabBar = widget.newTabBar
{
top = display.contentHeight - 50,
width = display.contentWidth,
backgroundFile = "assets/tabbar.png",
tabSelectedLeftFile = "assets/tabBar_tabSelectedLeft.png",
tabSelectedMiddleFile = "assets/tabBar_tabSelectedMiddle.png",
tabSelectedRightFile = "assets/tabBar_tabSelectedRight.png",
tabSelectedFrameWidth = 20,
tabSelectedFrameHeight = 52,
buttons = tabButtons
}
group: insert(tabBar)
composer.gotoScene("Home")
end
scene:addEventListener( "create", scene )
return scene
here is the method from the log in page that is supposed to access the tab bar page.
local function EnterPage( event )
composer.gotoScene("MainPage")
end
this is what the error is saying
stack traceback:
?: in function '?'
?: in function <?:703>
(tail call): ?
?: in function <?:122>
(tail call): ?
MainPage.lua:127: in main chunk
[C]: in function 'require'
?: in function <?:797>
(tail call): ?
LogIn.lua:78: in function <LogIn.lua:70>
?: in function <?:218>
line 127 of Main Page is the line that states "tabBar = widget.newTabBar"
The errors in the log in page just go to the gotoScene(MainPage) method

Answer 1

"File: ? Attempt to index a nil value" is very helpful: it says that you are doing an operation of the form a.b like a.b = something or a.b() where a is nil. Given the line it happens on, this is surely because you forgot
widget = require 'widget'
near the top of your file.
If that line is already there (in MainPage.lua), then check that widget hasn't been overwritten:
print('widget is', widget)
tabBar = widget.newTabBar
...
If it is not nil then you have made an error in the information you posted (wrong line number, etc) or maybe you tried many things and info got mixed up. You could try, just to be sure,
widget = require 'widget'
tabBar = widget.newTabBar
If that works, then you know you are overwriting widget somewhere in your MainPage.lua, in code not shown. You should also try
test = widget.newButton
{
left = 100, top = 200,
label = "Default",
onEvent = function() print('hi') end
}
If that works, but the newTabBar still doesn't work, try replacing your options with those of the example on corona newTabBar site.