we are doing a game with moving objects around frame-by-frame and also using accelerometer.
We have hooked on two events - about drawing the frame and for the acc.
The problem is, after we receive the acc event, we immediately put the x value in a variable.
Then we use this variable to move an object on the screen, but there is CONSIDERABLE slow down. ( I turn the phone, and after a second the object is moving properly, but a second is just way too much for a game, I expect immediate response).
What am I doing wrong? Is there another workaround to do this, or can I give some params to the accelerometer?
Unfortunately this is a serious problem - a real blocker. If this does not work, I have to find another solution (not Corona) for implementing the game.
Thanks in advance!!!
Danail
PS: here's some source:
local lastXGravity = 0
local function move(event)
eventTime=event.time
elapsedTime = eventTime - lastDrawTime
lastDrawTime = eventTime
xSpeed = lastXGravity
local xMoved = xSpeed * elapsedTime
object.x= object.x + xMoved
end
function acc(event)
lastXGravity = event.xGravity
end
Runtime:addEventListener("accelerometer", acc)
Runtime:addEventListener( "enterFrame", move )
I don't know anything about Corona development, but there are some general issues. First what is gravity containing? Just the gravity vector or total acceleration = gravity + userAcceleration? You will need to get userAcceleration = totalAcceleration - gravity or some member from event providing it directly, otherwise there is no chance.
If you have user acceleration, you need to integrate twice to get the position. See Equations of motion. In your case the code will be like:
velocity = userAcceleration * elapsedTime
position = 0.5*userAcceleration * elapsedTime^2
In general precise position detection by accelerometer and gyroscope is still an unresolved problem, so don't expect precise results. But if you are interested in just evaluating that there is an impulse in one direction, it might work. See for example Getting displacement from accelerometer data with Core Motion
The guys at Ansca's forum just got this out:
system.setAccelerometerInterval( 50 )
This didn't quite actually did the trick, but
system.setAccelerometerInterval( 100 ) -- warning - battery drainer!!
did it :)
I open-sourced my first Corona SDK-made game (which actually did really well) which uses Tilting in the same manner you describe (the more the tilt, the faster the movement and vice-versa).
It's called 'Tilt Monster' and you can download it here:
http://developer.anscamobile.com/code/tilt-monster
local isSimulator = "simulator" == system.getInfo("environment")
-- Accelerator is not supported on Simulator
if isSimulator then
-- Please display an Alert Box
end
-- Text parameters
local labelx = 50
local x = 220
local y = 95
local fontSize = 24
local frameUpdate = false
local xglabel = display.newText( "gravity x = ", labelx, y, native.systemFont, fontSize )
xglabel:setTextColor(255,255,255)
local xg = display.newText( "0.0", x, y, native.systemFont, fontSize )
xg:setTextColor(255,255,255)
y = y + 25
local yglabel = display.newText( "gravity y = ", labelx, y, native.systemFont, fontSize )
local yg = display.newText( "0.0", x, y, native.systemFont, fontSize )
yglabel:setTextColor(255,255,255)
yg:setTextColor(255,255,255)
y = y + 25
local zglabel = display.newText( "gravity z = ", labelx, y, native.systemFont, fontSize )
local zg = display.newText( "0.0", x, y, native.systemFont, fontSize )
zglabel:setTextColor(255,255,255)
zg:setTextColor(255,255,255)
y = y + 50
local xilabel = display.newText( "instant x = ", labelx, y, native.systemFont, fontSize )
local xi = display.newText( "0.0", x, y, native.systemFont, fontSize )
xilabel:setTextColor(255,255,255)
xi:setTextColor(255,255,255)
y = y + 25
local yilabel = display.newText( "instant y = ", labelx, y, native.systemFont, fontSize )
local yi = display.newText( "0.0", x, y, native.systemFont, fontSize )
yilabel:setTextColor(255,255,255)
yi:setTextColor(255,255,255)
y = y + 25
local zilabel = display.newText( "instant z = ", labelx, y, native.systemFont, fontSize )
local zi = display.newText( "0.0", x, y, native.systemFont, fontSize )
zilabel:setTextColor(255,255,255)
zi:setTextColor(255,255,255)
-- Create a circle that moves with Accelerator events
local centerX = display.contentWidth / 2
local centerY = display.contentHeight / 2
Circle = display.newCircle(0, 0, 20)
Circle.x = centerX
Circle.y = centerY
Circle:setFillColor( 0, 0, 255 ) -- blue
local textMessage = function( str, location, scrTime, size, color, font )
local x, t
size = tonumber(size) or 24
color = color or {255, 255, 255}
font = font or "Helvetica"
if "string" == type(location) then
if "Top" == location then
x = display.contentHeight/4
elseif "Bottom" == location then
x = (display.contentHeight/4)*3
else
-- Assume middle location
x = display.contentHeight/2
end
else
-- Assume it's a number -- default to Middle if not
x = tonumber(location) or display.contentHeight/2
end
scrTime = (tonumber(scrTime) or 3) * 1000 -- default to 3 seconds (3000) if no time given
t = display.newText(str, 0, 0, font, size )
t.x = display.contentWidth/2
t.y = x
t:setTextColor( color[1], color[2], color[3] )
-- Time of 0 = keeps on screen forever (unless removed by calling routine)
if scrTime ~= 0 then
-- Function called after screen delay to fade out and remove text message object
local textMsgTimerEnd = function()
transition.to( t, {time = 500, alpha = 0},
function() t.removeSelf() end )
end
-- Keep the message on the screen for the specified time delay
timer.performWithDelay( scrTime, textMsgTimerEnd )
end
return t -- return our text object in case it's needed
end -- textMessage()
local function xyzFormat( obj, value)
obj.text = string.format( "%1.3f", value )
-- Exit if not time to update text color
if not frameUpdate then return end
if value < 0.0 then
-- Only update the text color if the value has changed
if obj.positive ~= false then
obj:setTextColor( 255, 0, 0 ) -- red if negative
obj.positive = false
print("[---]")
end
else
if obj.positive ~= true then
obj:setTextColor( 255, 255, 255) -- white if postive
obj.positive = true
print("+++")
end
end
end
local function onAccelerate( event )
xyzFormat( xg, event.xGravity)
xyzFormat( yg, event.yGravity)
xyzFormat( zg, event.zGravity)
xyzFormat( xi, event.xInstant)
xyzFormat( yi, event.yInstant)
xyzFormat( zi, event.zInstant)
frameUpdate = false -- update done
-- Move our object based on the accelerator values
Circle.x = centerX + (centerX * event.xGravity)
Circle.y = centerY + (centerY * event.yGravity * -1)
-- Display message and sound beep if Shake'n
if event.isShake == true then
-- str, location, scrTime, size, color, font
textMessage( "Shake!", 400, 3, 52, {255, 255, 0} )
end
end
local function onFrame()
frameUpdate = true
end
-- Add runtime listeners
Runtime:addEventListener ("accelerometer", onAccelerate);
Runtime:addEventListener ("enterFrame", onFrame);
I hope, this code will help you.
Related
I've been using some extremely bulky code to detect collision between simple objects, and I've heard about bounding boxes. I can't find any tutorials on how to use it, so I'm asking about how to use it. Here is how I detect collision:
function platform.collision()
if player.x + player.width / 2 <= platform.x + platform.width and
player.x + player.width / 2 >= platform.x and
player.y + player.height <= platform.y + platform.height and
player.y + player.height >= platform.y then
The MDN has a rather concise article on 2D collision detection. Being the MDN, the examples are in javascript, but are easily translated to, and applicable in, any language - including Lua.
Let's take a look:
Axis-Aligned Bounding Box
One of the simpler forms of collision detection is between two rectangles that are axis aligned — meaning no rotation. The algorithm works by ensuring there is no gap between any of the 4 sides of the rectangles. Any gap means a collision does not exist.
Their example, translated to Lua:
local rect1 = { x = 5, y = 5, width = 50, height = 50 }
local rect2 = { x = 20, y = 10, width = 10, height = 10 }
if
rect1.x < rect2.x + rect2.width and
rect1.x + rect1.width > rect2.x and
rect1.y < rect2.y + rect2.height and
rect1.height + rect1.y > rect2.y
then
-- collision detected!
end
-- filling in the values =>
if
5 < 30 and
55 > 20 and
5 < 20 and
55 > 10
then
-- collision detected!
end
A live example, again in JavaScript, demonstrates this well.
Here's a quick (and imperfect) Love2D example you can throw into a main.lua and play around with.
local function rect (x, y, w, h, color)
return { x = x, y = y, width = w, height = h, color = color }
end
local function draw_rect (rect)
love.graphics.setColor(unpack(rect.color))
love.graphics.rectangle('fill', rect.x, rect.y,
rect.width, rect.height)
end
local function collides (one, two)
return (
one.x < two.x + two.width and
one.x + one.width > two.x and
one.y < two.y + two.height and
one.y + one.height > two.y
)
end
local kp = love.keyboard.isDown
local red = { 255, 0, 0, 255 }
local green = { 0, 255, 0, 255 }
local blue = { 0, 0, 255, 255 }
local dim1 = rect(5, 5, 50, 50, red)
local dim2 = rect(20, 10, 60, 40, green)
function love.update ()
if kp('up') then
dim2.y = dim2.y - 1
end
if kp('down') then
dim2.y = dim2.y + 1
end
if kp('left') then
dim2.x = dim2.x - 1
end
if kp('right') then
dim2.x = dim2.x + 1
end
dim2.color = collides(dim1, dim2) and green or blue
end
function love.draw ()
draw_rect(dim1)
draw_rect(dim2)
end
Oka explained it very well. This works for everything rectangular, not rotated and axis aligned. And you even already did it that way. This is great for buttons and the like!
But what I like doing is using (invisible) circles around objects and see if these collide. This works for everything where height is about the same as the width (which is the case for many sidescrolling platformers or top-down RPGs).
It's quite handy if you want to have the object centered at the current position. And it's especially helpful to simulate a finger on a touchscreen device, because a finger is quite a bit bigger than a mouse cursor. ;)
Here's an example on how to use this method. You can copy it as an actual game, it'll work.
--[[ Some initial default settings. ]]
function love.load()
settings = {
mouseHitbox = 5, -- A diameter around the mouse cursor.
-- For a finger (thouchscreen) this could be bigger!
}
objects = {
[1] = {
x = 250, -- Initial X position of object.
y = 200, -- Initial Y position of object.
hitbox = 100, -- A diameter around the CENTER of the object.
isHit = false -- A flag for when the object has been hit.
},
[2] = {
x = 400,
y = 250,
hitbox = 250,
isHit = false
}
}
end
--[[ This is the actual function to detect collision between two objects. ]]
function collisionDetected(x1,y1,x2,y2,d1,d2)
-- Uses the x and y coordinates of two different points along with a diameter around them.
-- As long as these two diameters collide/overlap, this function returns true!
-- If d1 and/or d2 is missing, use the a default diameter of 1 instead.
local d1 = d1 or 1
local d2 = d2 or 1
local delta_x = x2 - x1
local delta_y = y2 - y1
local delta_d = (d1 / 2) + (d2 / 2)
if ( delta_x^2 + delta_y^2 < delta_d^2 ) then
return true
end
end
--[[ Now, some LÖVE functions to give the collisionDetection() some context. ]]
function love.draw()
for i=1,#objects do -- Loop through all objects and draw them.
if ( objects[i].isHit ) then
love.graphics.setColor(255, 0, 0) -- If an object is hit, it will flash red for a frame.
objects[i].isHit = false
else
love.graphics.setColor(255, 255, 255)
end
love.graphics.circle("line", objects[i].x, objects[i].y, objects[i].hitbox/2)
end
end
-- You can use the following to check, if any object has been clicked on (or tapped on a touch screen device).
function love.mousepressed(x,y,button)
if ( button == 1 ) then
local i = objectIsHit(x,y) -- Check, if an object has been hit.
if ( i ) then
-- The object number 'i' has been hit. Do something with this information!
objects[i].isHit = true
end
end
end
function objectIsHit(x,y)
for i=1,#objects do -- Loop through all objects and see, if one of them has been hit.
if ( collisionDetected(x, y, objects[i].x, objects[i].y, settings.mouseHitbox, objects[i].hitbox) ) then
return i -- This object has been hit!
end
end
end
-- For the sake of completeness: You can use something like the following to check, if the objects themselves collide.
-- This would come in handy, if the objects would move around the screen and then bounce from each other, for example.
function love.update(dt)
if ( collisionDetected(objects[1].x, objects[1].y, objects[2].x, objects[2].y, objects[1].hitbox, objects[2].hitbox) ) then
-- The objects collided. Do something with this information!
end
end
As you can see, the collisionDetection() function is quite easy and intuitive to use.
Hopefully I could give you some more insight. And have fun with LÖVE 2D! :)
I am creating a game in which liquid will come out. I am using the particle systems of the physics engine of Corona. For the parameter of particle group, i get it from a method. When i run the program i get an error message saying that the parameter is a nil value.
Code:
-- Will randomly drop water stream at random locations and with random colors
--Delcare class variables
local physics = (require"physics")
physics.start()
local w = display.contentWidth
local h = display.contentHeight
local particleSystem = physics.newParticleSystem({
filename = "particle.png",
colorMixingStrength = 0.1,
radius = 3,
imageRadius = 6
})
--function to start the water stream
local function start()
end
--fucntion to end the water stream
local function stop()
end
--a function to create particle paramerters
-- flag to determine if the particle parameter should have random colors
-- WILL have RANDOM location
local function createParticleParameter(flag, x, y, color)
local param = {
flags = flags,
x = x,
y = y,
color = color,
radius = 10,
linearVelocityX = 0,
linearVelocityY = 10,
lifetime = 10
}
return param
end
local function onTimer()
local parmas = createParticleParameter("water", math.random(0, display.contentWidth), 0, {0, 1, 0})
particleSystem:createGroup(params)
end
timer.performWithDelay( 1000, onTimer, 0 )
The error message:
---------------------------
Corona Runtime Error
---------------------------
attempt to index a nil value
stack traceback:
[C]: in function 'createGroup'
main.lua:47: in function '_listener'
?: in function <?:167>
?: in function <?:221>
I checked if the parameter was right, and it was because when i ran this program it worked for some reason:
-- Will randomly drop water stream at random locations and with random colors
--Delcare class variables
local physics = (require"physics")
physics.start()
local w = display.contentWidth
local h = display.contentHeight
local particleSystem = physics.newParticleSystem({
filename = "particle.png",
colorMixingStrength = 0.1,
radius = 3,
imageRadius = 6
})
--function to start the water stream
local function start()
end
--fucntion to end the water stream
local function stop()
end
--a function to create particle paramerters
-- flag to determine if the particle parameter should have random colors
-- WILL have RANDOM location
local function createParticleParameter(flag, x, y, color)
local param = {
flags = flags,
x = x,
y = y,
color = color,
radius = 10,
linearVelocityX = 0,
linearVelocityY = 10,
lifetime = 10
}
return param
end
local function onTimer()
local parmas = createParticleParameter("water", math.random(0, display.contentWidth), 0, { 0,1,0})
particleSystem:createGroup({
flags = "water",
x = math.random(0, display.contentWidth),
y = 0,
color = {0, 1,0 },
radius = 10,
linearVelocityX = 0,
linearVelocityY = 10,
lifetime = 10
})
end
timer.performWithDelay( 1000, onTimer, 0 )
With the only major difference is that I manually placed the parameters.
Why is this happening?
You spelled params wrong
local parmas = createParticleParameter("water", math.random(0, display.contentWidth), 0, {0, 1, 0})
Im attempting to make a simple game app and keep running into this problem. I stopped programming in Lua for a few years so I don't exactly remember how to fix this. Anyway, my code is as follows:
EDIT: Here is the entire file. Still trying to figure out the formatting of Stack Overflow. Error occurs at line 76.
module(..., package.seeall)
-- Main function - MUST return a display.newGroup()
function new()
local localGroup = display.newGroup()
---------
local Rad = math.rad
local Sin = math.sin
local Cos = math.cos
local Pi = math.pi
local Atan2 = math.atan2
local radD = 180 / Pi
local DegR = Pi / 180
local touchPoint = display.newCircle(localGroup, -50, -50, 20)
touchPoint.isFocus = false
touchPoint.alpha = 0
function GetDistanceFromObjects(obj1, obj2)
local xDist = obj1.x - obj2.x
local yDist = obj1.y - obj2.y
local dist = Sqrt((xDist * xDist) + (yDist * yDist))
return dist
end
function getAngleDeg(inX1, inY1, inX2, inY2)
local xDist = inX2 - inX1
local yDist = inY2 - inY1
local angRad = Atan2(yDist, xDist)
return angRad * radD + 90
end
require "sprite"
function VectorFromAngle(inAngle, inVelocity)
local vx = Cos(Rad(inAngle-90))
local vy = Sin(Rad(inAngle-90))
if(inVelocity ~= nil)then
vx = vx * inVelocity
vy = vy * inVelocity
end
return vx,vy
end
require ( "physics" )
physics.start()
physics.setGravity( 1, 1 )
--( x, y )
--physics.setDrawMode ( "hybrid" )
math.randomseed(os.time())
local background = display.newImage("yazd.jpeg")
localGroup:insert(background)
--width of image divided by # of pics lined up from left to right (in the sprite) = the first #
--height of image divided by # of pics lined up from top to bottom (in the sprite) = the second #
local birdSheet = sprite.newSpriteSheet( "enemy.jpg", 59, 50 )
local birdSet = sprite.newSpriteSet(birdSheet, 1, 1)
-- images 1-14
sprite.add( birdSet, "bird", 1, 1, 200, 0 )
-- play 1-14, each image every 200 ms, 0 = loop count, which is infinite
local bird1 = sprite.newSprite( birdSet )
bird1.x = 40 -- starting point
bird1.y = 40 -- starting point
bird1.xScale = 0.5 --scale down x
bird1.yScale = 0.5 --scale down y
bird1:prepare("bird") --prepare sprite sequence
bird1:play() --play sprite
localGroup:insert(bird1)
--only local to this group
local killSheet = sprite.newSpriteSheet("explosion.png", 100, 100)
local killSet = sprite.newSpriteSet(killSheet, 1, 9)
sprite.add(killSet, "kill", 1, 9, 200, 1)
local birdCount = 1
local transDirection12
local function transDirection1()
bird1.xScale = 0.5
transition.to(bird1, {time=math.random(200,500), x = math.random(200,490), y = math.random(10,310), alpha = (math.random(9,100))/100, onComplete = transDirection12})
end
transDirection12 = function()
bird1.xScale = 0.5
transition.to(bird1, {time= math.random(200,500), x = math.random(200,490), y = math.random(10,310), alpha = (math.random(9,100))/100, onComplete = transDirection1})
end
transDirection1()
-- local transDirection1 declares what will be used (local function)
-- transDirection1 = function
-- following it are the function qualities
-- declares it will use object/image called bird1 and scales it to .5
-- time = ____ means it will take a certain time, between ____ and ____ to complete the transition
-- x=____ means that is where it will move to on the x axis
-- y=____ means that is where it will move to on the y axis
-- alpha = ___ means the is how transparent it will be
-- onComplete = ________ means that when the action is complete, it will call another function
-- The next function has the same qualities as transDirection1, but the onComplete part calls transDirection1 and they continue to loop
-- transDirection1() declares transDirection1 so the app knows about it and can use it
-- the other trans do not need to be declared because they are part of transDirection1, which is already declared
--(x, y, size.x, size.y)
local player = display.newImage( "mk11.png" )
player.x = 240
player.y = 260
player.xScale = .5
player.yScale = .5
localGroup:insert( player )
-- add physics to all the objects wanted: (object wanted, "static" or "dynamic")
physics.addBody(player, "static", {radius=30, isSensor = true})
physics.addBody(bird1, "static", {radius=23})
local function shoot(inPointX, inPointY)
-- (start at the x of the player + 10, also start at the y of the player, the radius of the circle is 5)
local bullet = display.newImage( "bullet2.png" )
bullet.x = player.x
bullet.y = player.y
-- add physics to the object, which is the bullet.
-- Make the bullet "dynamic" or moving
physics.addBody(bullet, "dynamic")
bullet.isFixedRotation = true
localGroup:insert( bullet )
local velocity = 300
local vx, vy = VectorFromAngle(player.rotation, velocity)
bullet.rotation = player.rotation
bullet:setLinearVelocity(vx, vy)
end
function RotateToTouchPoint(inPointX, inPointY)
local ang = getAngleDeg(player.x, player.y, inPointX, inPointY)
player.rotation = ang
end
local function ScreenTouchListener(event)
local phase = event.phase
if(phase == "began")then
if(touchPoint.isFocus == false)then
touchPoint.alpha = 1
touchPoint.x = event.x
touchPoint.y = event.y
display.getCurrentStage():setFocus(touchPoint, event.id)
touchPoint.isFocus = true
RotateToTouchPoint(event.x, event.y)
shoot(event.x, event.y)
end
elseif(touchPoint.isFocus)then
if(phase == "moved")then
touchPoint.x = event.x
touchPoint.y = event.y
RotateToTouchPoint(event.x, event.y)
elseif(phase == "ended" or phase == "cancelled")then
display.getCurrentStage():setFocus(touchPoint, nil)
touchPoint.isFocus = false
touchPoint.alpha = 0
end
end
return true
end
local function gotShot (event)
event.target:removeSelf()
event.other:removeSelf()
local explosion = sprite.newSprite(killSet)
explosion.x, explosion.y = event.target.x, event.target.y
explosion:prepare("kill")
explosion:play()
localGroup:insert( explosion )
birdCount = birdCount - 1
-- when there are no more birds, remove the runtime event listener and perform the
-- function with a delay of 500 m.s. The function changes the scene to test.lua
if "ended" then
if birdCount == 0 then
Runtime:removeEventListener("touch", ScreenTouchListener)
timer.performWithDelay(500, function()
director:changeScene("mainPage") end, 1)
end
end
end
bird1:addEventListener("collision", gotShot)
Runtime:addEventListener("touch", ScreenTouchListener)
---------
-- MUST return a display.newGroup()
return localGroup
end
Any help is appreciated!
The error message is perfectly clear -- the variable sprite used at this line:
local bird1 = sprite.birdSheet( birdSet )
has a nil value, meaning it has not been initialized or was set to nil. You need to show the earlier code where you should have set it up.
(After OP updates)
I think this line
require "sprite"
should actually be
sprite = require "sprite"
You can read more in modules tutorial here:
http://lua-users.org/wiki/ModulesTutorial
I have just started to learn LUA in school, but i cannot find many helpful tutorials o the internet to aid in my learning. I have made a simple game (which doesn't work yet, i realize that) and a main menu. However, when i try to start the app, it gives me this error:
/Users/jordanmcbride/Desktop/Lua Projects/Tapinator/main.lua:47: attempt to index global 'showCredits' (a nil value)
stack traceback:
/Users/jordanmcbride/Desktop/Lua Projects/Tapinator/main.lua:47: in main chunk
[Finished in 9.4s]
I have looked the error, and I cannot seem to understand how to fix it. The other questions have said something about returning the function returning a nil value, and that I should add a return statement to the end, but that doesn't work either.
Here is the code # line 47.
function showCredits.touch(e)
playButton.isVisible = false
creditsButton.isVisible = false
creditsView = display.newImage('credits.png', 0, display.contentHeight)
lastY = name.y
transition.to(name, {time = 300, y = display.contentHeight * 0.5 - title.height - 25})
transition.to(creditsView, {time = 300, y = display.contentHeight * 0.5 + creditsView.height, onComplete = function() creditsView:addEventListener('tap', hideCredits) end})
end
Here is my full code, in case the problem lies elsewhere:
display.setStatusBar(display.HiddenStatusBar)
radius = 40
smallTime = 200
bigTime = 800
score = 0
scoreInc = 2000
--HomePage
local name
local playButton
local creditsButton
local homePage
--Credits
local creditsPage
--Sounds
local circleSpawn = audio.loadSound( "circle_spawn.wav" )
local circleTap = audio.loadSound( "circle_tap.wav" )
function Main()
name = display.newImage('title.png', display.contentWidth / 2, 53)
name:scale( .5, .5 )
playButton = display.newImage('playButton.png', display.contentWidth / 2, 245)
playButton:scale( .5, .5 )
creditsButton = display.newImage('creditsButton.png', display.contentWidth / 2, 305)
creditsButton:scale( .5, .5 )
homePage = display.newGroup(name, playButton, creditsButton)
startButtonListeners('add')
end
function showCredits.touch(e)
playButton.isVisible = false
creditsButton.isVisible = false
creditsView = display.newImage('credits.png', 0, display.contentHeight)
lastY = name.y
transition.to(name, {time = 300, y = display.contentHeight * 0.5 - title.height - 25})
transition.to(creditsView, {time = 300, y = display.contentHeight * 0.5 + creditsView.height, onComplete = function() creditsView:addEventListener('tap', hideCredits) end})
end
function hideCredits.touch(e)
transition.to(creditsView, {time = 300, y = display.contentHeight, onComplete = function() creditsButton.isVisible = true playButton.isVisible = true creditsView:removeEventListener('tap', hideCredits) display.remove(creditsView) creditsView = nil end})
transition.to(name, {time = 300, y = lastY});
end
function startButtonListeners(action)
if(action == 'add') then
playButton:addEventListener('touch', playGame)
creditsButton:addEventListener('touch', showCredits)
else
playButton:removeEventListener('touch', playGame)
creditsButton:removeEventListener('touch', showCredits)
end
end
Main()
printScore = display.newText("Score: " .. tostring(score), display.contentWidth-80, 40, native.systemFontBold, 20)
-- A function that creates random circles
function generateCircle ()
-- Creates a new circle between 0 (the left most bounds) and the width of the display (being the content width), and also
-- 0 (the upper most bounds) and the height of the display (being the content height). The radius of the circle is 'radius'
x = math.random(radius, display.contentWidth-radius)
y = math.random(80, display.contentHeight)
score = score + scoreInc
myCircle = display.newCircle( x, y, radius )
myCircle:setFillColor( math.random(), math.random(), math.random() )
delayTime = math.random(smallTime, bigTime)
score = score + scoreInc
printScore.text = "Score:"..tostring(scores)
local spawnChannel = audio.play( circleSpawn )
timer.performWithDelay( delayTime, generateCircle )
end
generateCircle()
function myCircle:touch( event )
local tapChannel = audio.play( circleTap )
myCircle:removeSelf()
end
myCircle:addEventListener( "touch", myCircle )
The answer by greatwolf will work. But just a tip from my experience. One way I like to create functions is to try to define the name of the function first near the top of the lua file. Then I will define the function later on in the file. Something like this:
--function preallocation
local onPlayTap
local onSoundOnTap
local onSoundOffTap
local onCreditsTap
local onHelpTap
---------------------------------------------------------------------------------
-- Custom Function Definitions
---------------------------------------------------------------------------------
--Called when Sound On Button is tapped, turn off sound
onSoundOnTap = function(event)
end
--Called when Sound Off Button is tapped, turn on sound
onSoundOffTap = function(event)
end
--Called when Credits button is tapped, shows credits
onCreditsTap = function(event)
end
--Called when Help button is tapped, shows help
onHelpTap = function(event)
end
--Callback to Play button. Moves scene to Level Picker Scene
onPlayTap = function(event)
end
What this does is allow each function to be called by any other function in the file. If you do it the way you are doing it by adding the function name before the function like so:
local showCredits = {}
function showCredits.touch(e)
end
local hideCredits = {}
function hideCredits.touch(e)
end
your showCredit function will not be able to call the hideCredits function below it because the hideCredits variable has not been defined yet when the showCredit function was defined. Although this may not effect your current game, in future apps or games, you may need to call functions inside of other functions. To make this work properly, predefine all your function variables first, then define all your function afterwards. Hope this helps.
I need some help understanding how would I reset the score of numMiss, numHit, and numPercent back to 0 as soon as I tap the "reset.png" button and while doing so will also start the game from the beginning again.
Also, let me know if there are any corrections to be made within my code.
Heres what I have of the code so far
--width and height
WIDTH = display.contentWidth --320
HEIGHT = display.contentHeight --480
--display background
local p = display.newImageRect("park.png" ,500, 570)
p.x = WIDTH/2
p.y = HEIGHT/2
--display bouncing dog
local RADIUS = 5
local d = display.newImageRect("dogeball.png", 70, 70)
d.x = 50
d.y = 100
--display treat
local t = display.newImageRect("treat.png", 50, 50)
t.x = 245
t.y = math.random(HEIGHT)
--displays the reset button
local r = display.newImageRect("reset.png", 100,100)
r.x = 280
r.y = 480
--starting value of gravity and bounce(will change)
local GRAVITY = 0.3
local BOUNCE = 0.75
--downward force
local velocity = 0
--Tells the score to reset when true
local reset = false
--shows number of hits
local numHit = 0
--shows number of misses
local numMiss = 0
--Gets Percentage score
local numPercent = 0
--make hits and misses display
scoreHits = display.newText("Hits = " .. numHit, WIDTH/7, 1, native.systemFont, 18)
scoreMisses = display.newText("Misses = " .. numMiss, WIDTH/2.1, 1, native.systemFont, 18)
scorePercent = display.newText("Hit % = " .. numPercent, WIDTH/1.2, 1, native.systemFont, 18)
function enterFrame()
d.y = d.y + velocity
velocity = velocity + GRAVITY
local HIT_SLOP = RADIUS * 8 -- Adjust this to adjust game difficulty
if math.abs(t.x - d.x) <= HIT_SLOP
and math.abs(t.y - d.y) <= HIT_SLOP then
numHit = numHit + 1
scoreHits.text = "Hits = " .. numHit
--count 1 hit once dog and treat hit eachother
if (t.x - d.x) <= HIT_SLOP and (t.y - d.y) <= HIT_SLOP then
t.x = 400 --resets treat postioning
t.y = math.random(HEIGHT) --gives treat a random y coordinate
end
end
--puts the barrier at the bottom of the screen and tells dog to bounce from there
if (d.y > HEIGHT) then
d.y = HEIGHT
velocity = -velocity * BOUNCE
end
t.x = t.x - 5 --speed treat goes
if t.x < -350 then--position of the treat
t.x = 400
scoreMisses.text = "Misses = " .. numMiss
else if t.x < -100 then
t.y = math.random(HEIGHT) --random height after treat goes past dog
else if t.x < -99 then
numMiss = numMiss + 1 --calculates misses when goes past screen
scoreMisses.text = "Misses = " .. numMiss
end
end
end
--calculate percentage hits
numPercent = 100 * numHit / (numHit + numMiss)
scorePercent.text = "Hit % = " .. math.round(numPercent) --prints and rounds percentage
function tapped(event) --when tapped on reset, score gets reset
--reset function goes here
end
end
r:addEventListener( "tap", tapped )
end
function touched(event)
-- print(event.phase)
if event.phase == "began" then
velocity = velocity - 6 -- thrusts dog
end
return true
end
Runtime:addEventListener( "enterFrame" , enterFrame )
Runtime:addEventListener( "touch", touched )
To make your image a button you need to add an event listener that responds to touch or tap events.
see http://docs.coronalabs.com/api/event/touch/index.html
Or you use the widget library which gives you the possibility to use a blank button background and set only the label for each button what will be very handy when you include translations for other languages.
see http://docs.coronalabs.com/api/library/widget/newButton.html
In my game I have a function gameInit() that sets the hole game and all variables. This function is called when the game starts and also when the player wants to do a reset as it over writes the old variables. (there are other technics, depending on the complexity of your game and if you for example want to store the game settings for the next time the player starts the game)