sampleAct.lua

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--
-- sampleAct.lua
--
-- A sample activity (map, etc.) the Mars App
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-- Get local reference to the game globals
local game = globalGame

-- Create the act object
local act = game.newAct()


------------------------- Start of Activity --------------------------------

-- File local variables
local xyText		-- text display object for touch location 
local xyCenterText	-- text display object for touch location relative to center
local ufos = {}		-- array of UFO objects


-- Make a blue circle centered at the given position
local function makeBlueCircle( x, y )
	local c = display.newCircle( act.group, x, y, 20 )
	c:setFillColor( 0, 0, 1 )  -- blue
	return c
end

-- Handle touches on the background by updating the text displays
local function touched( event )
	-- Get touch location but pin to the act bounds
	local x = game.pinValue( event.x, act.xMin, act.xMax )
	local y = game.pinValue( event.y, act.yMin, act.yMax )

	-- Update the absolute and center-relative coordinate displays
	xyText.text = string.format( "(%d, %d)", x, y )
	xyCenterText.text = string.format( "Center + (%d, %d)", x - act.xCenter, y - act.yCenter )
end

-- Init the act
function act:init()
	-- Background image with touch listener
	local bg = act:newImage( "Canyon480x800.jpg", { width = act.width } )
	bg:addEventListener( "touch", touched )

	-- Crosshair in the center
	local dxy = 20
	display.newLine( act.group, act.xCenter - dxy, act.yCenter, act.xCenter + dxy, act.yCenter )
	display.newLine( act.group, act.xCenter, act.yCenter - dxy, act.xCenter, act.yCenter + dxy )
	
	-- Small green circles at the corners
	makeBlueCircle( act.xMin, act.yMin )
	makeBlueCircle( act.xMin, act.yMax )
	makeBlueCircle( act.xMax, act.yMin )
	makeBlueCircle( act.xMax, act.yMax )

	-- Touch location text display objects
	local yText = act.yMin + 100   -- relative to actual top of screen
	xyText = act:newText( "", act.xMin + act.width / 3, yText )
	xyCenterText = act:newText( "", act.xMin + act.width * 2/3, yText )

	-- Flying UFO
	local xStart = act.xMin - 100       -- start off screen to the left
	local yStart = act.yCenter - 142    -- height from center is consistent relative to background image
	for i=1, 2 do
		ufo = act:newImage( "ufo.png", { x = xStart, y = yStart + math.random(-12,12), height = 25 } )
		if i>1 then 					-- if this isn't the first ufo, take the last ufo's x and subtract 48 from it
			ufo.x = ufos[i-1].x-48
		end
		ufos[i] = ufo
	end
end

-- Handle enterFrame events
function act:enterFrame( event )
	for i=1, #ufos do
		-- Move UFO to the right and wrap around exactly at screen edges
		ufos[i].x = ufos[i].x + 7
		if ufos[i].x > act.xMax + ufos[i].width / 2 then
			ufos[i].x = act.xMin - ufos[i].width / 2
			ufos[i].y = ufos[i].y
		end
	end
end

------------------------- End of Activity --------------------------------


-- Corona needs the scene object returned from the act file
return act.scene