@Override
    public void write(JmeExporter ex) throws IOException {
        super.write(ex);
        OutputCapsule oc = ex.getCapsule(this);
        oc.write(screen, "screen", "");
    }
Serialize this event, for example when saving to a J3O file.

@param ex exporter (not null)
@throws IOException from exporter
jme3-niftygui/src/main/java/com/jme3/cinematic/events/GuiEvent.java