Help with collision needed

Getting Started Newbie Questions
#1

I am creating a game with a ball and a player and when the ball touches the player , the restart.lua scene shows up . But when the ball touches the player nothing happens . Can someone help me with this ?

game.lua :

 ball = display.newImage("ball1.png") ball.x = 400 ball.y = 160 ball.myName = "ball" player = display.newImage("player.png") player.x = 100 player.y = 300 player.myName = "player" local function loopObject() local objectDown= function() transition.to(player, { time=600, y=20, onComplete=loopObject }) end transition.to(player, { time=600, y=300, onComplete=objectDown }) end loopObject() local options = { effect = "fade", time = 400 } local function onGlobalCollision( event ) if ( event.phase == "began" ) then print( "began: " .. event.object1.myName .. " and " .. event.object2.myName ) elseif ( event.phase == "ended" ) then print( "ended: " .. event.object1.myName .. " and " .. event.object2.myName ) end end
#2

It’s because there is nothing going on in your collision function. It just prints values, you have to put the code inside the onGlobalCollision function. Actually, a local collision function would probably be better to use on the player.

#3

Like this ?

local function onPlayerCollision( event ) if event.phase =="began" then composer.gotoScene("restart", options) end end
#4

Yes, and make sure to add the eventListener:

player:addEventListener("collision")
#5

This is what I have :

local function onPlayerCollision( event ) if event.phase =="began" then composer.gotoScene("restart", options) end end function scene:show(event) local sceneGroup = self.view local phase = event.phase if ( phase == "will" ) then print("show started") player:addEventListener("onPlayerCollision") elseif ( phase == "did" ) then print("show showing objects") Runtime:addEventListener("touch", onTouch) end end function scene:hide(event) local sceneGroup = self.view local phase = event.phase if ( phase == "will" ) then print("hide started") composer.removeScene( "start" ) player:removeEventListener("onPlayerCollision") elseif ( phase == "did" ) then print("hide removing objects") Runtime:removeEventListener("touch", onTouch) end end

And I’m constantly getting this error :

ERROR: Runtime error 11:49:33.912 addEventListener: listener cannot be nil: nil 11:49:33.912 stack traceback: 11:49:33.912 [C]: in function 'error' 11:49:33.912 ?: in function 'getOrCreateTable' 11:49:33.912 ?: in function 'addEventListener' 11:49:33.912 ?: in function 'addEventListener' 11:49:33.912 ?: in function 'addEventListener' 11:49:33.912 C:\Users\user\Documents\Corona Projects\app\game.lua:96: in function '?' 11:49:33.912 ?: in function 'dispatchEvent' 11:49:33.912 ?: in function '\_nextTransition' 11:49:33.912 ?: in function \<?:1492\> 11:49:33.912 (tail call): ? 11:49:33.912 ?: in function '?' 11:49:33.912 ?: in function \<?:182\> 11:49:35.521

This is line 96 :

player:addEventListener("onPlayerCollision")

I also tried :

 player:addEventListener("onCollision")
#6

Sorry my bad:

player.collision = onPlayerCollision player:addEventListener("collision")
#7

Nearly there.  You’ve told it to look for a collision, but not where to go when it detects one.  Look in the API refs for event listeners and read the bit about how to call them properly…

#8

You can also do:

player:addEventListener("collision", onPlayerCollision)
#9

I have this :

local function onPlayerCollision( event ) if event.phase =="began" then print("Touched") end end function scene:show(event) local sceneGroup = self.view local phase = event.phase if ( phase == "will" ) then print("show started") elseif ( phase == "did" ) then print("show showing objects") player:addEventListener("collision", onPlayerCollision) Runtime:addEventListener("touch", onTouch) end end function scene:hide(event) local sceneGroup = self.view local phase = event.phase if ( phase == "will" ) then print("hide started") composer.removeScene( "start" ) elseif ( phase == "did" ) then print("hide removing objects") player:addEventListener("collision", onPlayerCollision) Runtime:removeEventListener("touch", onTouch) end end

And now nothing is happening no errors or anything

#10

First of all on if phase == “did”, you have to remove the collision listener, not add it again.

Also, when you say nothing is happening, did the player ever collide with anything?

#11

Try replacing this:

player:addEventListener("collision", onPLayerCollision)

with this:

player.collision = onPlayerCollision player:addEventListener("collision")
#12

Yes the player collided with the ball . 

I have this now :

local function onPlayerCollision( event ) if event.phase =="began" then print("Touched") end end function scene:show(event) local sceneGroup = self.view local phase = event.phase if ( phase == "will" ) then print("show started") elseif ( phase == "did" ) then print("show showing objects") player.collision = onPlayerCollision player:addEventListener("collision") Runtime:addEventListener("touch", onTouch) end end function scene:hide(event) local sceneGroup = self.view local phase = event.phase if ( phase == "will" ) then print("hide started") composer.removeScene( "start" ) elseif ( phase == "did" ) then print("hide removing objects") player.collision = onPlayerCollision player:removeEventListener("collision") Runtime:removeEventListener("touch", onTouch) end end

And still nothing happened . The console didn’t print anything .

#13

The line that says: 

local function onPLayerCollision(event)

Add self as a parameter too:

local function onPlayerCollision(self, event)
#14

Still nothing in the console :

local function onPlayerCollision( self, event ) if event.phase =="began" then print("Touched") end end
#15

Let me know if you need more code .

#16

Really? Can you send me your project zipped up?

#17

I don’t have zip . I hate it .

#18

But I can give you the code in my game.lua

#19

Oh. I have started doing this:

function anim:collision(event) if event.phase == "began" then print("Touched") end end anim:addEventListener("collision")
#20

Ok.