Class DelegatingDropAdapter
- All Implemented Interfaces:
EventListener
,DropTargetListener
,SWTEventListener
DelegatingDropAdapter
is a DropTargetListener
that maintains and delegates to a set of TransferDropTargetListener
s.
Each TransferDropTargetListener
can then be implemented as if it
were the DropTarget's only DropTargetListener
.
On dragEnter
, dragOperationChanged
,
dragOver
and drop
, a current listener is
obtained from the set of all TransferDropTargetListeners
. The
current listener is the first listener to return true
for
TransferDropTargetListener.isEnabled(DropTargetEvent)
. The current
listener is forwarded all DropTargetEvents
until some other
listener becomes the current listener, or the drop terminates.
After adding all TransferDropTargetListeners
to the
DelegatingDropAdapter
the combined set of Transfers
should be set in the SWT DropTarget
.
#getTransfers()
provides the set of Transfer
types
of all TransferDropTargetListeners
.
The following example snippet shows a DelegatingDropAdapter
with
two TransferDropTargetListeners
. One supports dropping resources
and demonstrates how a listener can be disabled in the isEnabled method. The
other listener supports text transfer.
final TreeViewer viewer = new TreeViewer(shell, SWT.NONE);
DelegatingDropAdapter dropAdapter = new DelegatingDropAdapter();
dropAdapter.addDropTargetListener(new TransferDropTargetListener() {
public Transfer getTransfer() {
return ResourceTransfer.getInstance();
}
public boolean isEnabled(DropTargetEvent event) {
// disable drop listener if there is no viewer selection
if (viewer.getSelection().isEmpty())
return false;
return true;
}
public void dragEnter(DropTargetEvent event) {}
public void dragLeave(DropTargetEvent event) {}
public void dragOperationChanged(DropTargetEvent event) {}
public void dragOver(DropTargetEvent event) {}
public void drop(DropTargetEvent event) {
if (event.data == null)
return;
IResource[] resources = (IResource[]) event.data;
if (event.detail == DND.DROP_COPY) {
// copy resources
} else {
// move resources
}
}
public void dropAccept(DropTargetEvent event) {}
});
dropAdapter.addDropTargetListener(new TransferDropTargetListener() {
public Transfer getTransfer() {
return TextTransfer.getInstance();
}
public boolean isEnabled(DropTargetEvent event) {
return true;
}
public void dragEnter(DropTargetEvent event) {}
public void dragLeave(DropTargetEvent event) {}
public void dragOperationChanged(DropTargetEvent event) {}
public void dragOver(DropTargetEvent event) {}
public void drop(DropTargetEvent event) {
if (event.data == null)
return;
System.out.println(event.data);
}
public void dropAccept(DropTargetEvent event) {}
});
viewer.addDropSupport(DND.DROP_COPY | DND.DROP_MOVE, dropAdapter.getTransfers(), dropAdapter);
- Since:
- 3.0
-
Constructor Summary
-
Method Summary
Modifier and TypeMethodDescriptionvoid
Adds the givenTransferDropTargetListener
.void
dragEnter
(DropTargetEvent event) The cursor has entered the drop target boundaries.void
dragLeave
(DropTargetEvent event) The cursor has left the drop target boundaries.void
The operation being performed has changed (usually due to the user changing a drag modifier key while dragging).void
dragOver
(DropTargetEvent event) The cursor is moving over the drop target.void
drop
(DropTargetEvent event) Forwards this event to the current listener, if there is one.void
dropAccept
(DropTargetEvent event) Forwards this event to the current listener if there is one.Transfer[]
Returns the combined set ofTransfer
types of allTransferDropTargetListeners
.boolean
isEmpty()
Returnstrue
if there are no listeners to delegate events to.void
Removes the givenTransferDropTargetListener
.
-
Constructor Details
-
DelegatingDropAdapter
public DelegatingDropAdapter()
-
-
Method Details
-
addDropTargetListener
Adds the givenTransferDropTargetListener
.- Parameters:
listener
- the new listener
-
dragEnter
The cursor has entered the drop target boundaries. The current listener is updated, and#dragEnter()
is forwarded to the current listener.- Specified by:
dragEnter
in interfaceDropTargetListener
- Parameters:
event
- the drop target event- See Also:
-
dragLeave
The cursor has left the drop target boundaries. The event is forwarded to the current listener.- Specified by:
dragLeave
in interfaceDropTargetListener
- Parameters:
event
- the drop target event- See Also:
-
dragOperationChanged
The operation being performed has changed (usually due to the user changing a drag modifier key while dragging). Updates the current listener and forwards this event to that listener.- Specified by:
dragOperationChanged
in interfaceDropTargetListener
- Parameters:
event
- the drop target event- See Also:
-
dragOver
The cursor is moving over the drop target. Updates the current listener and forwards this event to that listener. If no listener can handle the drag operation theevent.detail
field is set toDND.DROP_NONE
to indicate an invalid drop.- Specified by:
dragOver
in interfaceDropTargetListener
- Parameters:
event
- the drop target event- See Also:
-
drop
Forwards this event to the current listener, if there is one. Sets the current listener tonull
afterwards.- Specified by:
drop
in interfaceDropTargetListener
- Parameters:
event
- the drop target event- See Also:
-
dropAccept
Forwards this event to the current listener if there is one.- Specified by:
dropAccept
in interfaceDropTargetListener
- Parameters:
event
- the drop target event- See Also:
-
getTransfers
Returns the combined set ofTransfer
types of allTransferDropTargetListeners
.- Returns:
- the combined set of
Transfer
types
-
isEmpty
public boolean isEmpty()Returnstrue
if there are no listeners to delegate events to.- Returns:
true
if there are noTransferDropTargetListeners
false
otherwise
-
removeDropTargetListener
Removes the givenTransferDropTargetListener
. Listeners should not be removed while a drag and drop operation is in progress.- Parameters:
listener
- the listener to remove
-