Simple remote on demand image caching.

app.js

var iconStore = Ti.Filesystem.applicationDataDirectory + '/CachedRemoteImages';
var dir = Ti.Filesystem.getFile(iconStore);
if (!dir.exists()) {
    dir.createDirectory();
}
function cacheRemoteURL(image, imageURL) {
    if (imageURL) {
        var hashedSource = Ti.Utils.md5HexDigest(imageURL + '') + '.' + imageURL.split('.').pop();
        var localIcon = Ti.Filesystem.getFile(iconStore, hashedSource);
        if (localIcon.exists()) {
            image.image = localIcon.nativePath;
        }
        else {
            image.image = imageURL;
            image.addEventListener('load', function() {
                localIcon.write(image.toImage());
            });
        }
    }
}


var win = Ti.UI.createWindow();
var image = Ti.UI.createImageView();
cacheRemoteURL(image, 'http://www.appcelerator.com/wp-content/themes/appcelerator/img/APPC_logo.png');
win.add(image);
win.open();