How do you callback the name of a display object inserted in a display group?

Getting Started Newbie Questions
#1

Generated using a loop, there are tile display objects laid next to each other. Each tile is assigned a name using tile.name = i, the i starting with 1 and ending with tile number. The tiles are stored in a display group, and a touch handler is added to display group.

When I touch the tile group, I’d like to get a return on the name value of the individual tile touched. But, print(event.target.name) doesn’t work since event.target refers to the display group.

What can I do to refer to the individual tile when touched?

Thanks in advance.

#2

You’ll have to parse all the objects and see which one the <x,y> position is ‘within’ or  add touch listeners to the tiles instead.

#3

Well, if you know the size of the tiles and all tiles are layed out next to each other, you can estimate the tiles index as well.

local tileSize = 50 --width and height of each tile local gridWidth = 10 --number of tiles in one row local function estimateTileIndex(x, y) return math.floor(x/tileSize) + math.floor(y/tileSize)\*gridWidth + 1 end --assume the most upper left tiles upper left corner is at position 0,0 print(estimateTileIndex(130, 270) --returns 53

The above example works, if you lay out your tiles from left to right and from top to bottom.

#4

Try this:

local tileGroup = display.newGroup( ) local tileLis = function ( e ) local currentTile = e.target if (e.phase == "began") then print( currentTile.name ) end end for i = 1, 5 do local currentTile = display.newRect( tileGroup,25, 25+(50\*(i-1)), 50, 50 ) currentTile.name = i currentTile:addEventListener( "touch", tileLis ) end
#5

Thank you all for your responses. They were really helpful. I managed to get it to work.

Below is a demonstration of what I was really trying to do. I am creating a level selection scene that would allow me to swipe from one theme to the next. Please let me know if there’s anything I could do to improve the code given that my purpose is to create a level selection scene.

local count = 0 local pageTotal = 3 local tileTouchHandler local scroller local w, h = display.contentWidth, display.contentHeight local cX, cY = display.contentCenterX, display.contentCenterY local abs = math.abs local pageScroll = display.newGroup() pageScroll.anchorX = 0; pageScroll.anchorY = 0 local scrollMinX, scrollMaxX = 0, -(pageTotal - 1) \* w local startX = 0 local slideX = 0 local function scroller(event) local pageNum = event.target.name if event.phase == 'began' then slideX = pageScroll.x - event.x elseif event.phase == 'moved' then if scrollMinX \>= pageScroll.x and pageScroll.x \> scrollMaxX then pageScroll.x = event.x + slideX end elseif event.phase == 'ended' then -- Scroller touch released if abs(event.x - event.xStart) \>= 150 then if (event.x - event.xStart) \< 0 then -- Move Right if pageNum ~= pageTotal then transition.to( pageScroll, {time = 300, x = startX - 640}) startX = startX - 640 end else -- Move Left if pageNum ~= 1 then transition.to( pageScroll, {time = 300, x = startX + 640}) startX = startX + 640 end end else transition.to( pageScroll, {time = 300, x = startX}) end end end local pageNum = 0 for i = 1, pageTotal do local page = display.newRect(pageScroll, pageNum \* w, 0, w,h ) page.anchorX = 0; page.anchorY = 0 page.name = i page:addEventListener('touch', scroller) if i == 2 then page:setFillColor(1,0,0,0.5) elseif i == 3 then page:setFillColor(0,0,1,0.5) end pageNum = pageNum + 1 end
#6

You’ll have to parse all the objects and see which one the <x,y> position is ‘within’ or  add touch listeners to the tiles instead.

#7

Well, if you know the size of the tiles and all tiles are layed out next to each other, you can estimate the tiles index as well.

local tileSize = 50 --width and height of each tile local gridWidth = 10 --number of tiles in one row local function estimateTileIndex(x, y) return math.floor(x/tileSize) + math.floor(y/tileSize)\*gridWidth + 1 end --assume the most upper left tiles upper left corner is at position 0,0 print(estimateTileIndex(130, 270) --returns 53

The above example works, if you lay out your tiles from left to right and from top to bottom.

#8

Try this:

local tileGroup = display.newGroup( ) local tileLis = function ( e ) local currentTile = e.target if (e.phase == "began") then print( currentTile.name ) end end for i = 1, 5 do local currentTile = display.newRect( tileGroup,25, 25+(50\*(i-1)), 50, 50 ) currentTile.name = i currentTile:addEventListener( "touch", tileLis ) end
#9

Thank you all for your responses. They were really helpful. I managed to get it to work.

Below is a demonstration of what I was really trying to do. I am creating a level selection scene that would allow me to swipe from one theme to the next. Please let me know if there’s anything I could do to improve the code given that my purpose is to create a level selection scene.

local count = 0 local pageTotal = 3 local tileTouchHandler local scroller local w, h = display.contentWidth, display.contentHeight local cX, cY = display.contentCenterX, display.contentCenterY local abs = math.abs local pageScroll = display.newGroup() pageScroll.anchorX = 0; pageScroll.anchorY = 0 local scrollMinX, scrollMaxX = 0, -(pageTotal - 1) \* w local startX = 0 local slideX = 0 local function scroller(event) local pageNum = event.target.name if event.phase == 'began' then slideX = pageScroll.x - event.x elseif event.phase == 'moved' then if scrollMinX \>= pageScroll.x and pageScroll.x \> scrollMaxX then pageScroll.x = event.x + slideX end elseif event.phase == 'ended' then -- Scroller touch released if abs(event.x - event.xStart) \>= 150 then if (event.x - event.xStart) \< 0 then -- Move Right if pageNum ~= pageTotal then transition.to( pageScroll, {time = 300, x = startX - 640}) startX = startX - 640 end else -- Move Left if pageNum ~= 1 then transition.to( pageScroll, {time = 300, x = startX + 640}) startX = startX + 640 end end else transition.to( pageScroll, {time = 300, x = startX}) end end end local pageNum = 0 for i = 1, pageTotal do local page = display.newRect(pageScroll, pageNum \* w, 0, w,h ) page.anchorX = 0; page.anchorY = 0 page.name = i page:addEventListener('touch', scroller) if i == 2 then page:setFillColor(1,0,0,0.5) elseif i == 3 then page:setFillColor(0,0,1,0.5) end pageNum = pageNum + 1 end