Preload all sound and images before starting animation

Question

I'm building a simple animation web app that involves sound and images. I want it so that when a user enters the site they see a "now loading" page, and when all the images and audio files are done loading it calls a function that starts the animation. So far the code I have is roughly this:

var img1, img2;
var sound1, sound2;

function loadImages() {
    img1=new Image();
    img1.src="...";
    img2=new Image();
    img2.src="...";
    img1.onload=img2.onload=handleImageLoad;
}

function loadSound() {
    createjs.Sound.registerSound({id:"sound1", src:"sound1.wav"});
    createjs.Sound.registerSound({id:"sound2", src:"sound2.wav"}); 
    createjs.Sound.addEventListener("fileload", handleSoundLoad);
}

function handleImageLoad(e) {
    //Do something when an image loads
}

function handleSoundLoad(e) {
    //Do something when a sound loads
    if(e.id=="sound1") sound1 = createjs.Sound.createInstance("sound1");
    else if(e.id=="sound2") sound2 = createjs.Sound.createInstance("sound2");
}

$(document).ready(function() {
    //overlay a "now loading" .gif on my canvas
    ...
    ...

    loadSound(); 
    loadImages();
}

// call this when everything loads
function start() {
    //remove "now loading..." overlay .gif
    ...
    ...

    //start animating
}

handleImageLoad() and handleSoundLoad() are invoked independently of each other so I can't rely on them on calling start() . How can I figure out when everything is loaded? What callback function(s) can I use to achieve this?

Answer 1

Using the built-in SoundJS registerSound method is not bad, but PreloadJS will handle both Sounds and images (and other types) in a single queue. Check out the examples in the PreloadJS GitHub.

http://preloadjs.com and http://github.com/CreateJS/PreloadJS/

Answer 2

This is probably not the best solution, but I did something similar this way:

var lSnd = false;
var lImg = false;

$(document).ready(function(){
 setInterval(checkLoadComplete,1000);
});

function loadSound(){
  //loadingSound
  //on load complete call= soundLoadingComplite();
}

function soundLoadingComplite(){
  //do some stuff
  lSnd = true;
}
function loadImages(){
  //loadingImages
  //on load complete call= imageLoadingComplite();
}

function imageLoadingComplite(){
  //do some stuff
  lSnd = true;
}

function checkLoadComplete(){
  if(lSnd&&lImg){
    startAnimation();
    //clear interval
 }
}

Hope this helps.

Answer 3

I'd be doing it this way:

function loadSound(){
    songOK = false;

    song = new Audio()
    song.src = uri;
    song.addEventListener('canplaythrough', function(){ songOK = true; }, false)

    return songOK;
}

function loadImage(){
    pictOK = false;
    pict = new Image();
    pict.src = uri;

    pict.onload = function (){
        pictOK = true;
    }
    return pictOK;
}

function loadMedia(){
    startNowLoading();

    if( loadSound() && loadImage())
        stopNowLoading();
    else
        kaboom();   //something went wrong!        
}

$(document).ready(function(){
    loadMedia();
}

This should allow you to execute the functions in sequence.