如何在Flex列表控件中实现自定义拖动功能？

Flex has built in drag-n-drop for list controls, and allows you to override this. But they don't cover this in examples. The built-in functionality automatically drags the list-item, if you want to override this you find the handlers are being set up on the list itself. What I specifically want to do, is my TileList shows small thumbnails of items I can drag onto a large Canvas. As I drag an item from the list, the drag proxy should be a different image.Flex has built in drag-n-drop for list controls