A few days ago I posted about how setting the useRollOver style to false on a List control also prevents the itemRollOver event from firing on that same control:
Flex: Changing useRollOver style affects itemRollOver event
In other words, what I thought would only affect the visual appearance of a component turned out to also have an impact on the components logic. I realized that some time ago I ran in to that same scenario in the context of drag & drop. I thought I'd share that here as well.
So, basically, I was implementing some drag and drop functionality for our application. When the user started a drag action I changed some parameters in the application to reflect that a dragging was currently under way. When the user stopped his dragging I was relying on the dragDropEvent to restore the application to its original state or update it depending on the drop location.
The above was implemented and was working fine. Next step was to show different cursor icons depending on which areas of the screen the user was currently dragging over, the green plus for allowed drop locations and the red cross for prohibited locations. This was easily accomplished by using the DragManager.showFeedback function passing it DragManager.COPY or DragManager.NONE respectively. Unfortunately it showed that this change also caused the implemented logic to fail. The dragDropEvent handler was just not invoked if the feedback was set to none.
Looking back at it now, I suppose it kind of makes sense and my implementation became a bit more clear after reorganizing it to account for the encountered issue. Still, it took me a while to figure it out and I also couldn't find any mentioning of this 'feature' in the documentation. It just doesn't feel right when changing the visual feedback of your application also affects the functionality. MVC, anyone?
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