Those who went to my Lotusphere session already know this but doing drag’n’drop in SWT is actually quite easy. All you need to do is define a drag source and/or a drop target. The former is only required if a control in users should be able to drag data from a control in your code. The latter is required if you would like users to be able to drop stuff onto your component.
When setting up a drag source or a drop target you specify the control the source/target controls and the types of data you can provide/accept. These types are called Transfer types and are subclasses of the org.eclipse.ui.dnd.Transfer class.
Transfer types that might come handy – the class names should be pretty self-explanatory:
- org.eclipse.swt.dnd.URLTransfer.getInstance()
- org.eclipse.swt.dnd.FileTransfer.getInstance()
- org.eclipse.swt.dnd.TextTransfer.getInstance()
Making a JFace viewer a drop target is simple passing in the underlying control:
DropTarget dropTarget = new DropTarget(viewer.getControl(), DND.DROP_DEFAULT | DND.DROP_MOVE);
Once the drop target has been created you set the transfer types:
final Transfer[] dropTransferTypes = new Transfer[] {
type1,
type2
};
dropTarget.setTransfer(dropTransferTypes);
The last thing you need is to add an instance of DropTargetListener or use a subclass of DropTargetAdapter as I do here:
dropTarget.addDropListener(new DropTargetAdapter() {
...
...
});
Creating a drag source is analogous.
