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Corona SDK Example – Load Progress Bar – The Rambling Programmer
Oct 132011
 

This example demonstrates a progress bar that updates while assets are being loaded.  The typical use is when your assets are large enough that the user might think your app has frozen if there isn’t some sort of feedback.

A few notes about the code below:

  • Because of the way that the Corona SDK scopes modules, I chose to have a global “World State” variable declared in main.lua so I can share values between modules. The name I chose for that variable is: gWS.  So if you see values prefaced with “gWS.” they are global values declared in main.lua
  • The gWS.nScaleX and gWS.nScaleY values are used to let me switch devices and have everything scale properly.
  • This example uses the “ui” and “director” modules from Ansca (included in the complete code on GitHug
  • The code is under the MIT license so feel free to use, modify, etc the code to your hearts content.

You can get the full source code along with assets from GitHub here

---------------------------------------------------------------------------------------
-- Date: October 12, 2011
--
-- Version: 1.0
--
-- File name: cSceneLoad.lua
--
-- Code type: Example Code
--
-- Author: Ken Rogoway
--
-- Update History:
--
-- Comments: The space images used are from NASA and are in the public domain.
--           The horse image sheets are from the horse demo provided by Ansca.
--
-- Sample code is MIT licensed:
-- Permission is hereby granted, free of charge, to any person obtaining a copy
-- of this software and associated documentation files (the "Software"), to deal
-- in the Software without restriction, including without limitation the rights
-- to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-- copies of the Software, and to permit persons to whom the Software is
-- furnished to do so, subject to the following conditions:

-- The above copyright notice and this permission notice shall be included in
-- all copies or substantial portions of the Software.

-- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-- IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-- FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-- AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-- LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-- OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
-- THE SOFTWARE.
--
-- Copyright (C) 2011 Ken Rogoway. All Rights Reserved.
---------------------------------------------------------------------------------------

module(..., package.seeall)

local bUseListener = false
local nMeterX = 272     -- final X position of the meter bar when at 100 percent
local nMeterY = 562     -- Y position of the meter bar
local nMeterW = 480     -- Width of my meter bar image
local nMeterH = 30      -- Height of my meter bar image

-- This is set to 1/2 second (500 ms) so let it go slow enough to
-- see the bar advance since we are using a very small set of data
-- You would want to set this to a much smaller value, so there is
-- minimal delay between chunks, but probably at least 1/30 of a
-- second (33 ms) so there is time to update the display.
local nDelayBetweenChunks = 500

-- Main function - MUST return a display.newGroup()
function new()
    local splashGroup = display.newGroup()
    local loadingImage, loadingBar, loadingMask

    loadingImage = display.newImageRect( gWS.pImageDir.."load_bkgd.png", display.contentWidth, display.contentHeight )
    splashGroup:insert( loadingImage )
    loadingImage.x = display.contentCenterX
    loadingImage.y = display.contentCenterY

    loadingBar = display.newImageRect( gWS.pImageDir.."load_bar.png", math.floor( nMeterW * gWS.nScaleX ), math.floor( nMeterH * gWS.nScaleY ) )
    splashGroup:insert( loadingBar )

    loadingBar:setReferencePoint( display.TopLeftReferencePoint )
    loadingBar.x = math.floor( (nMeterX-nMeterW) * gWS.nScaleX )
    loadingBar.y = math.floor( nMeterY * gWS.nScaleY )

    loadingMask = display.newImageRect(	gWS.pImageDir.."load_mask.png", display.contentWidth, display.contentHeight )
    splashGroup:insert( loadingMask )

    loadingMask.x = display.contentCenterX
    loadingMask.y = display.contentCenterY

    -- Update the percent complete bar
    function updateBar()
        local nPercent = math.floor( 100 * (gWS.nLoadIndex-1) / gWS.nLoadCount )
        --print( "Percent = ", nPercent )
        loadingBar.x = math.floor( (nMeterX-nMeterW + (nMeterW*nPercent/100)) * gWS.nScaleX )
        if ( nPercent >= 100 ) then
            -- final resting place at 100 percent
            loadingBar.x = math.floor( nMeterX * gWS.nScaleX )
        end
    end

    function myLoadChunk()
        -- Load a chunk of data
        gWS.pAssetLoader.LoadChunk()

        if ( bUseListener == false ) then
            -- update the loading bar.  See the comments above
            -- regarding using a event to trigger this
            updateBar()
        end

        -- Are there any chunks remaining?  If so, set a timer to
        -- load the next one.
        if ( gWS.nLoadIndex <= gWS.nLoadCount ) then
            timer.performWithDelay( nDelayBetweenChunks, myLoadChunk )
        else
            -- Done, so finish any data stuff
            gWS.pAssetLoader.Shutdown()

            if ( bUseListener == true ) then
                Runtime:removeEventListener( "enterFrame", updateBar )
            end

            -- Onward and outward
            director:changeScene( "cSceneGame" )
        end
    end

    -- Set everything up so we can start going
    gWS.pAssetLoader.Initialize()

    updateBar()	-- update it once for 0 percent

    -- Start it going
    timer.performWithDelay( nDelayBetweenChunks, myLoadChunk )

    if ( bUseListener == true ) then
        Runtime:addEventListener( "enterFrame", updateBar )
    end

    clean = function()

        if loadingImage then
            display.remove( loadingImage )
            loadingImage = nil
        end

        if loadingBar then
            display.remove( loadingBar )
            loadingBar = nil
        end

        if loadingMask then
            display.remove( loadingMask )
            loadingMask = nil
        end
    end

    -- MUST return a display.newGroup()
    return splashGroup
end

 

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 Posted by at 5:50 am

  2 Responses to “Corona SDK Example – Load Progress Bar”

  1. BTW, I did some reading on auto-scaling on the Ansca website, and it looks like they handle a lot of this for you as long as you set things up properly in your xxx file and use newImageRect() instead of newImage().

    I haven’t switched my project over yet from using my scale factors to using the content scaling feature, but when I do I will write about that subject.

    Here are some great links:

    http://developer.anscamobile.com/content/configuring-projects#Dynamic_Content_Scaling
    http://blog.anscamobile.com/2010/11/content-scaling-made-easy/

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