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JList class provides the
setDropMode method which supports the following drop modes.
JList is
DropMode.USE_SELECTION.
When dragging in this mode, the selected item in the list
moves to echo the potential drop point. On a drop the
selected item shifts to the drop location.
This mode is provided for backwards compatibility
but is otherwise not recommended.
DropMode.ON, the selected item
in the list moves to echo the potential drop point, but the
selected item is not affected on the drop. This mode
can be used to drop on top of existing list items.
DropMode.INSERT, the user is restricted to
selecting the space between existing list items,
or before the first item
or after the last item in the list. Selecting existing
list items is not allowed.
DropMode.ON_OR_INSERT is a combination
of the ON and INSERT modes.
The JTree class provides the same set of
drop modes and the JTable class has
several more specific to adding rows or columns.
To obtain the location of the drop, the
TransferSupport class provides the
getDropLocation method that returns the precise point
where the drop has occurred. But for a list component, the index of
the drop is more useful than a pixel location, so
JList provides a special subclass, called
JList.DropLocation. This class provides the
getIndex and
isInsert methods, which handle the math for you.
The table, tree, and text components each provide an implementation
of DropLocation with methods that make the most sense for
each component.
The
JTable.setDropMode method has the most choices.
The following table shows the methods for all four classes:
JList.DropLocation |
JTree.DropLocation |
JTable.DropLocation |
JTextComponent.DropLocation |
|---|---|---|---|
isInsert |
getChildIndex |
isInsertRow |
getIndex |
getIndex |
getPath |
isInsertColumn |
getBias |
getRow | |||
getColumn |
Next is a demo that implements a custom transfer handler for a list component so that it fully participates in drag and drop.
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