How to do this?

[ricardo.repp]

hi, i have a little problem im working on my first project is a game with a rocket in the space, the rocket has to evade the enemies, the rocket only moves up and down, and i have a code from a user here on this page but im only understand it from parts, is a code of a line following the rocket like a fire leaving behind. my problem is when i reload the scene with my reload button all of my objects works perfectly but the line starts to paint for all the screen.

i think my problem is when i reload all the scene im not reloading the line and its paints again, but i don’t know how to reload the line like my other objects

this is an example of my image group in the scene.

local storyboard = require ("storyboard") local scene = storyboard.newScene() function scene:createScene(event) local screenGroup = self.view object = display.newImage("rocket.png") object:scale(0.023,0.023) object.x = 113 object.y = 160 physics.addBody( object, "dynamic", physicsData:get("rocket") ) screenGroup:insert(object) end

and this is the code of the line following the rocket

xpos = { x = 0 } -- A proxy object for the exhaust local my\_line, prevx, prevy local X = 90 local TimePerScreen = 2000 local NumberOfScreens = 2 local FinalX = -NumberOfScreens \* display.contentWidth transition.to(xpos, { time = TimePerScreen \* NumberOfScreens, x = FinalX, iterations = -1, -- Repeat forever onRepeat = function() transition.to(my\_line, { -- Move the old line the rest of the way off screen... time = TimePerScreen, x = my\_line.x - display.contentWidth, onComplete = my\_line:removeSelf() }) my\_line = nil -- ...and start a new one. prevx = prevx - FinalX -- Correct the previous x to account for the split end }) timer.performWithDelay(5, function() local x, y = xpos.x, object.y if x == FinalX then -- x might still be a big negative value for a few frames x = 0 end if x ~= prevx or y ~= prevy then if my\_line then -- line already exists? my\_line.x = X + x my\_line:append(X, y) elseif prevx then -- previous point exists? my\_line = display.newLine(X + prevx, prevy, X, y) my\_line:setStrokeColor( 0,0.6,0.9 ) my\_line.strokeWidth = 20 my\_line.alpha= 0.3 end prevx, prevy = x, y end end, 0) function scene:enterScene(event) end function scene:exitScene(event) end function scene:destroyScene(event) end scene:addEventListener("createScene", scene) scene:addEventListener("enterScene", scene) scene:addEventListener("exitScene", scene) scene:addEventListener("destroyScene", scene) return scene

My question is how to put the object my_line in the image group to reload it with my other objects together

sorry if i not express my self correctly im learning english.

[daniel.strmecki]

You should insert all scene objects (including your line) to scene group, like you did here:

[lua]

screenGroup:insert(object)

[/lua]

Daniel

[ricardo.repp]

Hello Daniel, thank you for your answer but if i do that screenGroup:insert(my_line) i have this error

attempt to call method ‘append’ (a nil value) stack traceback

pdd. the code of my_line only throw me the error when i reload the scene.

[StarCrunch]

Hi!

Sorry, I gave you something for demonstration purposes, so it does need a little work. 

In addition to what Daniel says, you should get the handles to those control objects. So these lines change:

local xpos\_transition = transition.to(xpos, { -- ... local exhaust\_timer = timer.performWithDelay(5, function()

You don’t want some of that stuff sticking around between scenes. These objects go on forever, if not stopped, so they’re a problem. Also, some of that “prev” stuff assumes the line is still intact. So in your exitScene (or hide , in Composer), you then want to do:

timer.cancel(exhaust\_timer) transition.cancel(xpos\_transition) display.remove(my\_line) -- probably exists, but account for first two frames or so xpos.x = 0 exhaust\_timer, xpos\_transition, my\_line, prevx, prevy = nil

Also, then you would make the transition and timer each time, in enterScene (or show , in Composer), instead of once when you require the file. In that case, it might be easier to stuff these values into your scene (say, scene.my_line instead of my_line ).

[ricardo.repp]

Hi starCrunch thank you for helping me again i follow your instructions and this is my code now

local storyboard = require ("storyboard") local scene = storyboard.newScene() function scene:createScene(event) local screenGroup = self.view object = display.newImage("rocket.png") object:scale(0.023,0.023) object.x = 113 object.y = 160 physics.addBody( object, "dynamic", physicsData:get("rocket") ) screenGroup:insert(object) xpos = { x = 0 } -- A proxy object for the exhaust local my\_line, prevx, prevy local X = 90 local TimePerScreen = 2000 local NumberOfScreens = 2 local FinalX = -NumberOfScreens \* display.contentWidth local xpos\_transition = transition.to(xpos, { time = TimePerScreen \* NumberOfScreens, x = FinalX, iterations = -1, -- Repeat forever onRepeat = function() transition.to(my\_line, { -- Move the old line the rest of the way off screen... time = TimePerScreen, x = my\_line.x - display.contentWidth, onComplete = my\_line:removeSelf() }) my\_line = nil -- ...and start a new one. prevx = prevx - FinalX -- Correct the previous x to account for the split end }) local exhaust\_timer = timer.performWithDelay(5, function() local x, y = xpos.x, object.y if x == FinalX then -- x might still be a big negative value for a few frames x = 0 end if x ~= prevx or y ~= prevy then if my\_line then -- line already exists? my\_line.x = X + x my\_line:append(X, y) elseif prevx then -- previous point exists? my\_line = display.newLine(X + prevx, prevy, X, y) my\_line:setStrokeColor( 0,0.6,0.9 ) my\_line.strokeWidth = 20 my\_line.alpha= 0.3 screenGroup:insert(my\_line) end prevx, prevy = x, y end end, 0) end function scene:enterScene(event) end function scene:exitScene(event) timer.cancel(exhaust\_timer)transition.cancel(xpos\_transition) display.remove(my\_line) -- probably exists, but account for first two frames or so xpos.x = 0 exhaust\_timer, xpos\_transition, my\_line, prevx, prevy = nil endend function scene:destroyScene(event) end scene:addEventListener("createScene", scene) scene:addEventListener("enterScene", scene) scene:addEventListener("exitScene", scene) scene:addEventListener("destroyScene", scene) return scene

when the games retry i got this error

attempt to index a nil value

stack traceback:

in function ‘cancel’

what im doing wrong?

thank u again

[StarCrunch]

Hi.

I’m about to go to sleep, but I’ll try to quickly give you some hints.

First, you probably want that stuff in enterScene , not createScene.

As for the error, that’s why I mentioned that you might want to put those in the scene instead (the note about scene.my_line , for example). In your code right now, the local variables are stuck inside the scope of createScene , and exitScene can’t see them.

[ricardo.repp]

sorry for the time, and thank you again for your help im now understand  what are you saying, and sorry for my ignorance im learning and i want to learn have a great night!

[daniel.strmecki]

You should insert all scene objects (including your line) to scene group, like you did here:

[lua]

screenGroup:insert(object)

[/lua]

Daniel

[ricardo.repp]

Hello Daniel, thank you for your answer but if i do that screenGroup:insert(my_line) i have this error

attempt to call method ‘append’ (a nil value) stack traceback

pdd. the code of my_line only throw me the error when i reload the scene.

[StarCrunch]

Hi!

Sorry, I gave you something for demonstration purposes, so it does need a little work. 

In addition to what Daniel says, you should get the handles to those control objects. So these lines change:

local xpos\_transition = transition.to(xpos, { -- ... local exhaust\_timer = timer.performWithDelay(5, function()

You don’t want some of that stuff sticking around between scenes. These objects go on forever, if not stopped, so they’re a problem. Also, some of that “prev” stuff assumes the line is still intact. So in your exitScene (or hide , in Composer), you then want to do:

timer.cancel(exhaust\_timer) transition.cancel(xpos\_transition) display.remove(my\_line) -- probably exists, but account for first two frames or so xpos.x = 0 exhaust\_timer, xpos\_transition, my\_line, prevx, prevy = nil

Also, then you would make the transition and timer each time, in enterScene (or show , in Composer), instead of once when you require the file. In that case, it might be easier to stuff these values into your scene (say, scene.my_line instead of my_line ).

[ricardo.repp]

Hi starCrunch thank you for helping me again i follow your instructions and this is my code now

local storyboard = require ("storyboard") local scene = storyboard.newScene() function scene:createScene(event) local screenGroup = self.view object = display.newImage("rocket.png") object:scale(0.023,0.023) object.x = 113 object.y = 160 physics.addBody( object, "dynamic", physicsData:get("rocket") ) screenGroup:insert(object) xpos = { x = 0 } -- A proxy object for the exhaust local my\_line, prevx, prevy local X = 90 local TimePerScreen = 2000 local NumberOfScreens = 2 local FinalX = -NumberOfScreens \* display.contentWidth local xpos\_transition = transition.to(xpos, { time = TimePerScreen \* NumberOfScreens, x = FinalX, iterations = -1, -- Repeat forever onRepeat = function() transition.to(my\_line, { -- Move the old line the rest of the way off screen... time = TimePerScreen, x = my\_line.x - display.contentWidth, onComplete = my\_line:removeSelf() }) my\_line = nil -- ...and start a new one. prevx = prevx - FinalX -- Correct the previous x to account for the split end }) local exhaust\_timer = timer.performWithDelay(5, function() local x, y = xpos.x, object.y if x == FinalX then -- x might still be a big negative value for a few frames x = 0 end if x ~= prevx or y ~= prevy then if my\_line then -- line already exists? my\_line.x = X + x my\_line:append(X, y) elseif prevx then -- previous point exists? my\_line = display.newLine(X + prevx, prevy, X, y) my\_line:setStrokeColor( 0,0.6,0.9 ) my\_line.strokeWidth = 20 my\_line.alpha= 0.3 screenGroup:insert(my\_line) end prevx, prevy = x, y end end, 0) end function scene:enterScene(event) end function scene:exitScene(event) timer.cancel(exhaust\_timer)transition.cancel(xpos\_transition) display.remove(my\_line) -- probably exists, but account for first two frames or so xpos.x = 0 exhaust\_timer, xpos\_transition, my\_line, prevx, prevy = nil endend function scene:destroyScene(event) end scene:addEventListener("createScene", scene) scene:addEventListener("enterScene", scene) scene:addEventListener("exitScene", scene) scene:addEventListener("destroyScene", scene) return scene

when the games retry i got this error

attempt to index a nil value

stack traceback:

in function ‘cancel’

what im doing wrong?

thank u again

[StarCrunch]

Hi.

I’m about to go to sleep, but I’ll try to quickly give you some hints.

First, you probably want that stuff in enterScene , not createScene.

As for the error, that’s why I mentioned that you might want to put those in the scene instead (the note about scene.my_line , for example). In your code right now, the local variables are stuck inside the scope of createScene , and exitScene can’t see them.

[ricardo.repp]

sorry for the time, and thank you again for your help im now understand  what are you saying, and sorry for my ignorance im learning and i want to learn have a great night!