Detecting whether content successfully loaded in a UILoader component in Flash using ActionScript 3.0

// ActionScript 3.0
/* Requires:
 * - UILoader component in Flash library
 */
import fl.containers.UILoader;
 
var uiLoader:UILoader = new UILoader();
uiLoader.addEventListener(IOErrorEvent.IO_ERROR, uiLoader_ioError);
uiLoader.source = "http://www.helpexamples.com/flash/images/404.jpg";
addChild(uiLoader);
 
function uiLoader_ioError(evt:IOErrorEvent):void {
    var tf:TextField = new TextField();
    tf.text = evt.text;
    tf.autoSize = TextFieldAutoSize.LEFT;
    tf.width = 300;
    tf.wordWrap = true;
    tf.x = 10;
    tf.y = 10;
    addChild(tf);
}