Event listner wont remove

Getting Started Newbie Questions
#1

In my createScene I have the following code
 

 local function onKeyEvent(event) local keyName = event.keyName local phase = event.phase local returnValue = false if(keyName == "back" and phase == "up") then local options = { effect = "slideRight", time = 500, } storyboard.gotoScene("start\_menu", options) returnValue = true end return returnValue end Runtime:addEventListener("key", onKeyEvent)

and in my exitScene I have the following code

function scene:exitScene(event) local group = self.view Runtime:removeEventListener("key", onKeyEvent) end

for some reason the exit scene gets called buy the listener never gets removed.

#2

Dumb question but do you have the same event listener in the scene you are transitioning to?

#3

Yes I do, is that a problem?

#4

Are you sure the old listener isn’t removed?  Perhaps it is, and in your new scene you are re-creating the same listener

#5

I’m not positive that it’s not removed I’m removing it the same exact way as above just in a different scene. In my code though I have a print statement after the back button is pressed and I print out what scene is calling it and it’s the current scene not the other one so I’m pretty sure the old scene listener is being removed. I hope that makes sense.

#6

To be safe, try removing the whole event listener in the second scene and seeing if it still fires post-transition.

#7

Okay remove it from which one? This is how my scnes go

main > start_menu > lobby

The issue I’m having is when I do the following

main > start_menu > lobby > start_menu > lobby > start_menu

Everytime I go back into the lobby it creates a new listener that wont get removed. So which one should I remove the listener from to test?

#8

Actually I lied the main and start_menu don’t have the listener on it only the lobby does.

#9

Is there a reason you’re not putting that in main.lua and leaving it?

#10

Umm I suppose I could…never really thought about that. Is there an easy way to get what scene is loaded in corona other then setting it insde a var myself?

#11

storyboard.getCurrentSceneName() see:

http://docs.coronalabs.com/api/library/storyboard/getCurrentSceneName.html

Unless you need the keyboard handler to do something different each scene (beyond specifying a different scene name to go back to), then it make sense to put it in each scene.  In programming there is a principle called the DRY principle.  Don’t repeat yourself.  if you have 30 scenes and you have to write that back handler 30 times, that’s a lot of work. 

What I would more likely do is put it all in main.lua and then in each scene, during the enterScene() function, set a variable that can be seen from main.lua (yea, it begs for a global, but wait!)   like adding a variable to the storyboard table called .goBackTo

So if your in level1.lua and the back button should take you back to menu.lua then do:

storyboard.goBackTo = “menu”

Then in your one function in main.lua you can say if the back button was hit, storyboard.gotoScene(storyboard.goBackTo)

Easy as pie.

#12

Yeah that makes a lot of sense…I have a hard time with lua/corona with scope issues and trying to find code sometimes. I’ve developed a place all the code in 1 file per scene approach and if I need it more then once make it a class. It may not be the best approach but it’s helped me keep everything in place. I should rethink that approach though as I can see what you’re talking about.

P.S. moving it to the main.lua worked just fine

#13

Dumb question but do you have the same event listener in the scene you are transitioning to?

#14

Yes I do, is that a problem?

#15

Are you sure the old listener isn’t removed?  Perhaps it is, and in your new scene you are re-creating the same listener

#16

I’m not positive that it’s not removed I’m removing it the same exact way as above just in a different scene. In my code though I have a print statement after the back button is pressed and I print out what scene is calling it and it’s the current scene not the other one so I’m pretty sure the old scene listener is being removed. I hope that makes sense.

#17

To be safe, try removing the whole event listener in the second scene and seeing if it still fires post-transition.

#18

Okay remove it from which one? This is how my scnes go

main > start_menu > lobby

The issue I’m having is when I do the following

main > start_menu > lobby > start_menu > lobby > start_menu

Everytime I go back into the lobby it creates a new listener that wont get removed. So which one should I remove the listener from to test?

#19

Actually I lied the main and start_menu don’t have the listener on it only the lobby does.

#20

Is there a reason you’re not putting that in main.lua and leaving it?