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Position objects on a grid
local GRID_WIDTH = 8
local GRID_HEIGHT = 8
local CELL_WIDTH = 40
local CELL_HEIGHT = 40
--
-- Create a 2D array to hold our objects.
local grid = {}
for i = 1, GRID_HEIGHT do
grid[i] = {}
end
--
-- load the background image:
local checkerBoard = display.newImageRect("table.png", 320, 320)
checkerBoard.x = display.contentCenterX
checkerBoard.y = display.contentCenterY
--
-- Calculate some values
--
local gbOffsetX = checkerBoard.x - ( checkerBoard.width * checkerBoard.anchorX )
local gbOffsetY = checkerBoard.y - ( checkerBoard.height * checkerBoard.anchorY )
--
-- Using positions 1, 8 for X and Y, draw the object at the right place in the grid
--
local function spawnPiece( xPos, yPos, pieceType )
if pieceType ~= "red" and pieceType ~= "white" then
print( "Invalid piece type", pieceType )
return nil
end
if xPos < 1 or xPos > GRID_WIDTH or yPos < 1 or yPos > GRID_HEIGHT then
print( "Position out of range:", xPos, yPos )
return nil
end
local piece = display.newImageRect( "token_" .. pieceType .. ".png", CELL_WIDTH, CELL_HEIGHT )
--
-- record the pieces logical position on the board
--
piece.xPos = xPos
piece.yPos = yPos
--
-- Position the piece
--
piece.x = (xPos - 1) * CELL_WIDTH + (CELL_WIDTH * 0.5) + gbOffsetX
piece.y = (yPos - 1) * CELL_HEIGHT + (CELL_HEIGHT * 0.5) + gbOffsetY
return piece
end
local function movePiece(piece, xPos, yPos )
-- check to see if the position is occupied. You can do either:
-- 1. "Capture the piece". This would involve removeing the piece
-- that is there before moving to the spot or
-- 2. "Reject the move" because the spot is occupied. For the purpose
-- of this tutorial we will reject the move.
--
if xPos < 1 or xPos > GRID_WIDTH or yPos < 1 or yPos > GRID_HEIGHT then
return false
end
if grid[yPos][xPos] == nil then -- got an empty spot
--
-- get the screen x, y for where we are moving to
--
local x = (xPos - 1) * CELL_WIDTH + (CELL_WIDTH * 0.5) + gbOffsetX
local y = (yPos - 1) * CELL_HEIGHT + (CELL_HEIGHT * 0.5) + gbOffsetY
--
-- save the old grid x, y
--
local oldXPos = piece.xPos
local oldYPos = piece.yPos
--
-- Move the object in the table
--
grid[yPos][xPos] = piece
grid[yPos][xPos].xPos = xPos
grid[yPos][xPos].yPos = yPos
grid[oldYPos][oldXPos] = nil
--
-- Now move the physical graphic
--
transition.to(grid[yPos][xPos], { time = 500, x = x, y = y})
return true
end
end
--
-- Generate a few objects
--
--
-- a holding piece for moving the object
--
local lastObject
for i = 1, 10 do
local xPos = math.random( 1, GRID_WIDTH )
local yPos = math.random( 1, GRID_HEIGHT )
local color = "red"
if math.random(2) == 2 then
color = "white"
end
grid[yPos][xPos] = spawnPiece(xPos, yPos, color, checkerBoard)
lastObject = grid[yPos][xPos]
end
timer.performWithDelay(2000, function() movePiece( lastObject, 4, 5); end, 1)
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