MouseWheel Event not working

That is the nature of the plugin. Flash (and many OS's in general) only "activate" once the mouse has clicked on the application.

If you put your wheel listener on the stage you don't ever need to set stage.focus = stage;, the listener will work no matter what object you have selected, unless you explicitly stop propagation. 

This "you must click" nature is present for other events in flash such as the keyboard event. You've probably noticed on many flash games that using keyboard controls won't work until you "click" (activate) the Flash plugin. This is the same thing. Even when testing in the Flash IDE (CTRL+ENTER/CTRL+SHIFT+ENTER). You must click the window to start the events.

Open a new AS3 document to see this example show you that focus of any MovieClip you have on stage doesn't have anything to do with the wheel responding. Just paste this code into frame 1 and test. Until you click the window you shouldn't receive feedback from the wheel. There is a red box. On mouse roll over or click I set focus to the red square, yet the mouse wheel still fires off perfectly fine.

Example:

import flash.display.MovieClip; import flash.events.MouseEvent; // global wheel listener stage.addEventListener(MouseEvent.MOUSE_WHEEL, onWheel); // function to trace when wheel is spin function onWheel(e:MouseEvent):void {           trace("MouseWheel: " + e.delta); } // generate MovieClip (red box) var box:MovieClip = new MovieClip(); box.graphics.beginFill(0xFF0000,1); box.graphics.drawRect(50,50,200,200); box.graphics.endFill(); addChild(box); // add a listener to the box just to allow focus changes box.addEventListener(MouseEvent.MOUSE_OVER, focusMe); box.addEventListener(MouseEvent.CLICK, focusMe); function focusMe(e:MouseEvent):void {           stage.focus = MovieClip(e.target); }

call

stage.focus = stage;

after any MouseEvents are processed