This is untested, but it should work. This just uses a ternary to choose between the two classes using the Capabilities class.
<s:List itemRenderer="{ ( Capabilitiles.os.toLowerCase().indexOf( 'ios' ) != -1 || Capabilities.os.toLowerCase().indexOf( 'android' ) != -1 ) ? MOBILECLASS : DESKTOPCLASS }" />
Alternatively, you could set it in AS3.
private function creationCompleteHandler( e:Event ):void {
if ( Capabilitiles.os.toLowerCase().indexOf( 'ios' ) != -1 || Capabilities.os.toLowerCase().indexOf( 'android' ) != -1 ) {
list.itemRenderer = MobileClass;
}
else {
list.itemRenderer = DesktopClass;
}
}
Again, that is untested. I know I have experienced some odd issues when trying to set the itemRenderer property, so it may not like this. Worth a shot, though.