Scene Management

The Ultimate Guide to Gideros Studio

Creating game flow and logic

Most applications and games have different scenes (e.g., menu, scoreboard, game levels, inventory, end-of-game, etc). A transition from one scene to another is usually started by user input or some other event. These transitions typically consist of the following steps:

   • Construct the new scene (e.g., load bitmaps, sprites, sounds)
   • Hide the original scene and show the new scene, often with some kind of special effect (e.g., crossfading)
   • Destroy the old scene

Luckily, a "Scene Manager" library is provided directly in Gideros. :-)

Scene Manager Usage Overview

Create a class for each of your scenes (and preferably put them into separate .lua files):

Menu = Core.class(Sprite)
Game = Core.class(Sprite)
EndScene = Core.class(Sprite)

Create a SceneManager instance passing a table with scene names as keys and your classes as values:

local sceneManager = SceneManager.new{
   ["menu"] = Menu,
   ["game"] = Game,
   ["endScene"] = EndScene,
}
stage:addChild(sceneManager)

Change between scenes with function SceneManager:changeScene(sceneName, duration, transition, ease) like so:

sceneManager:changeScene("game", 1, SceneManager.moveFromTop, easing.linear)

SceneManager dispatches events as it makes the transition from one scene to another (enterBegin, enterEnd, exitBegin, exitEnd). You can register to listen for these events to begin/end your animations, clear your timers, save the scores, etc.

Built-in Transition Effects

The scene manager library defines the following transition effects: Move functions

   • SceneManager.moveFromLeft
   • SceneManager.moveFromRight
   • SceneManager.moveFromBottom
   • SceneManager.moveFromTop
   • SceneManager.moveFromLeftWithFade
   • SceneManager.moveFromRightWithFade
   • SceneManager.moveFromBottomWithFade
   • SceneManager.moveFromTopWithFade

Overlay functions

   • SceneManager.overFromLeft
   • SceneManager.overFromRight
   • SceneManager.overFromBottom
   • SceneManager.overFromTop
   • SceneManager.overFromLeftWithFade
   • SceneManager.overFromRightWithFade
   • SceneManager.overFromBottomWithFade
   • SceneManager.overFromTopWithFade

Fade & flip functions

   • SceneManager.fade
   • SceneManager.crossFade
   • SceneManager.flip
   • SceneManager.flipWithFade
   • SceneManager.flipWithShade

Transition Events

The scene manager dispatches the following four events:

   • enterBegin: Dispatched when your new scene is about to enter the stage. You can initialize your variables here.
   • enterEnd: Dispatched after the transition of new scene has ended. Mostly, you add listeners and start your logic here.
   • exitBegin: Dispatched when your current scene is about to leave the stage. You can remove listeners and stop timers here.
   • exitEnd: Dispatched after your current scene has left the stage.

The following code shows an example scene (“MyScene”) and how you might use the “enterEnd” and “exitBegin” events:

MyScene = Core.class(Sprite)
function MyScene:init()
	self:addEventListener("enterEnd", self.onEnterEnd, self)
	self:addEventListener("exitBegin", self.onExitBegin, self)
end
function MyScene:onEnterEnd()
	self:addEventListener(Event.ENTER_FRAME, self.onEnterFrame, self)
	-- create your timers
	-- also you can add your player sprite
	-- and so on...
end
function MyScene:onExitBegin()
	self:removeEventListener(Event.ENTER_FRAME, self.onEnterFrame, self)
	-- stop your timers
	-- save score
	-- and so on...
end

PREV.: Classes in Gideros
NEXT: Introduction to Graphics