CODEWITHSUNDEEP
luacoronasdk
ZedBee
ZedBee

Reputation: 2378

self.view Objects Cleanup

I am trying to understand how to efficiently remove scene objects once a scene is destroyed. According to corona docs objects can be inserted to self.view in order to clean them up once a scene is destroyed.

Here is my code that I am trying

local composer = require( "composer")
local scene = composer.newScene()

local rects={}
local rectsNum = 0
local rectsCount = 0

local rectsTimer

local sceneGroup

local function rectTransComplete( obj )
    print("rectTransComplete .. called")

    rectsCount = rectsCount + 1

    if rectsCount == 3 then
        composer.removeScene("scene2")
    end
end

local function spawnRect( )
    print("inside spawnrects")
    rectsNum = rectsNum + 1
        rects[rectsNum] = display.newRect( display.contentWidth/2, 100, 100, 100)
        rects[rectsNum]:setFillColor( 1,1,1 )
        rects[rectsNum].id = numRect

        rects[rectsNum].transition = transition.to( rects[rectsNum], {time = 9000, y = display.contentHeight + 100,
                onComplete = rectTransComplete

        } )

    sceneGroup:insert( rects[rectsNum] )
end

function  scene:create( event )
    sceneGroup = self.view
end

function scene:show(event)
    print("inside create")
    if event.phase == "did" then
            rectsTimer = timer.performWithDelay( 1000, spawnRect, -1 )
        end
end

function scene:hide( event )
    -- body
end

function scene:destroy( event )
    timer.cancel( rectsTimer )
    print("scene Destroyed")
end

scene:addEventListener( "create", scene )
scene:addEventListener( "show", scene )
scene:addEventListener( "hide", scene )
scene:addEventListener( "destroy", scene )

return scene

I seems to work fine since all the rectangles are removed from the screen once the scene is destroyed but I see the app printing messages "rectTransComplete .. called" even after the scene is destroyed. Why is it so and why are the transitions not automatically cancelled once the objects are removed. Do I need to cancel all transitions manually by iterating through all the rectangles and cancel each transition. What about the rects table as it also contains references to the rects. Should I manually clean it up. If I need to manually clean everything (or most of the things), what exactly is the benefit of using self.view

Upvotes: 0

Views: 559

Answers (2)

Teddy Engel
Teddy Engel

Reputation: 1006

Just a note, you will also have the same problem if you ever use Runtime events to propagate events to your display objects.

I had the same issue a few days ago, there are 2 ways to approach this:

Method 1: You keep a reference to the opened transitions, iterate through all your references and call transition.cancel(transitionReference) on them.

Method 2: You create a listener in your rectangles objects, send a runtime event to the rectangles object when the scene is destroyed that triggers the listener, and inside the listener you "cancel" the transition linked to current rectangle (transition.cancel(rectangle)) You can have a look at this article if you need a howto to work with runtime events: http://www.engelteddy.com/softwaredevelopment/mobiledevelopment/observer-pattern-corona-sdk/

Upvotes: 1

iBad
iBad

Reputation: 286

You need to call transition.cancel() in scene:destroy function.

Upvotes: 0

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