NU-CCS-99-04.ps [ Readme | Copyright | Tutorial | Download | Feedback ]

Implementing Drag and Drop

The original BeanBox supports moving beans around the development window (inside the BeanBox container), but once we introduce multilevel nesting, things get more complex. The moving process is the same, done by propagating MouseEvents from the bean's wrapper to the BeanBox, and the BeanBox draws the red rectangle. What has changed is what happens when the operation is finished. The original BeanBox finishes the moving operation by setting a new position to the bean which was moved, but the ContextBox has to do a bit more. The ContextBox gets the innermost Container that is positioned at the coordinates where the move finished, and then checks two things:

• Is the target container either inside the bean being moved or inside its parent? If so, the bean is just being repositioned, as in the original BeanBox, and the operation is finished successfully.
• Otherwise, it checks whether the bean being moved can be placed inside the new BeanContext associated with the target container at the target position? If it cannot, the operation fails, but if it is possible to do so, the bean (besides putting it into the BeanContext) is also placed inside the target container and the operation finishes successfully.

NU-CCS-99-04.ps [ Readme | Copyright | Tutorial | Download | Feedback ]