public class DropTarget extends Widget
DropTarget
defines the target object for a drag and drop transfer.
IMPORTANT: This class is not intended to be subclassed.
This class identifies the Control
over which the user must position the cursor
in order to drop the data being transferred. It also specifies what data types can be dropped on
this control and what operations can be performed. You may have several DropTragets in an
application but there can only be a one to one mapping between a Control
and a DropTarget
.
The DropTarget can receive data from within the same application or from other applications
(such as text dragged from a text editor like Word).
int operations = DND.DROP_MOVE | DND.DROP_COPY | DND.DROP_LINK;
Transfer[] types = new Transfer[] {TextTransfer.getInstance()};
DropTarget target = new DropTarget(label, operations);
target.setTransfer(types);
The application is notified of data being dragged over this control and of when a drop occurs by
implementing the interface DropTargetListener
which uses the class
DropTargetEvent
. The application can modify the type of drag being performed
on this Control at any stage of the drag by modifying the event.detail
field or the
event.currentDataType
field. When the data is dropped, it is the responsibility of
the application to copy this data for its own purposes.
target.addDropListener (new DropTargetListener() {
public void dragEnter(DropTargetEvent event) {};
public void dragOver(DropTargetEvent event) {};
public void dragLeave(DropTargetEvent event) {};
public void dragOperationChanged(DropTargetEvent event) {};
public void dropAccept(DropTargetEvent event) {}
public void drop(DropTargetEvent event) {
// A drop has occurred, copy over the data
if (event.data == null) { // no data to copy, indicate failure in event.detail
event.detail = DND.DROP_NONE;
return;
}
label.setText ((String) event.data); // data copied to label text
}
});
Constructor and Description |
---|
DropTarget(Control control,
int style)
Creates a new
DropTarget to allow data to be dropped on the specified
Control . |
Modifier and Type | Method and Description |
---|---|
void |
addDropListener(DropTargetListener listener)
Adds the listener to the collection of listeners who will
be notified when a drag and drop operation is in progress, by sending
it one of the messages defined in the
DropTargetListener
interface. |
protected void |
checkSubclass()
Checks that this class can be subclassed.
|
<T> T |
getAdapter(java.lang.Class<T> adapter)
Implementation of the
Adaptable interface. |
Control |
getControl()
Returns the Control which is registered for this DropTarget.
|
DropTargetListener[] |
getDropListeners()
Returns an array of listeners who will be notified when a drag and drop
operation is in progress, by sending it one of the messages defined in
the
DropTargetListener interface. |
DropTargetEffect |
getDropTargetEffect()
Returns the drop effect for this DropTarget.
|
Transfer[] |
getTransfer()
Returns a list of the data types that can be transferred to this DropTarget.
|
void |
removeDropListener(DropTargetListener listener)
Removes the listener from the collection of listeners who will
be notified when a drag and drop operation is in progress.
|
void |
setDropTargetEffect(DropTargetEffect effect)
Specifies the drop effect for this DropTarget.
|
void |
setTransfer(Transfer[] transferAgents)
Specifies the data types that can be transferred to this DropTarget.
|
addDisposeListener, addListener, checkWidget, dispose, getData, getData, getDisplay, getListeners, getStyle, isDisposed, isListening, notifyListeners, removeDisposeListener, removeListener, removeListener, reskin, setData, setData, toString
public DropTarget(Control control, int style)
DropTarget
to allow data to be dropped on the specified
Control
.
Creating an instance of a DropTarget may cause system resources to be allocated
depending on the platform. It is therefore mandatory that the DropTarget instance
be disposed when no longer required.control
- the Control
over which the user positions the cursor to drop the datastyle
- the bitwise OR'ing of allowed operations; this may be a combination of any of
DND.DROP_NONE, DND.DROP_COPY, DND.DROP_MOVE, DND.DROP_LINKSWTException
- SWTError
- NOTE: ERROR_CANNOT_INIT_DROP should be an SWTException, since it is a recoverable error, but can not be changed due to backward compatibility.
Widget.dispose()
,
checkSubclass()
,
DND.DROP_NONE
,
DND.DROP_COPY
,
DND.DROP_MOVE
,
DND.DROP_LINK
public void addDropListener(DropTargetListener listener)
DropTargetListener
interface.
dragEnter
is called when the cursor has entered the drop target boundaries
dragLeave
is called when the cursor has left the drop target boundaries and just before
the drop occurs or is cancelled.
dragOperationChanged
is called when the operation being performed has changed
(usually due to the user changing the selected modifier key(s) while dragging)
dragOver
is called when the cursor is moving over the drop target
dropAccept
is called just before the drop is performed. The drop target is given
the chance to change the nature of the drop or veto the drop by setting the event.detail
field
drop
is called when the data is being dropped
listener
- the listener which should be notifiedjava.lang.IllegalArgumentException
- SWTException
- DropTargetListener
,
getDropListeners()
,
removeDropListener(org.eclipse.swt.dnd.DropTargetListener)
,
DropTargetEvent
protected void checkSubclass()
Widget
The SWT class library is intended to be subclassed
only at specific, controlled points (most notably,
Composite
and Canvas
when
implementing new widgets). This method enforces this
rule unless it is overridden.
IMPORTANT: By providing an implementation of this method that allows a subclass of a class which does not normally allow subclassing to be created, the implementer agrees to be fully responsible for the fact that any such subclass will likely fail between SWT releases and will be strongly platform specific. No support is provided for user-written classes which are implemented in this fashion.
The ability to subclass outside of the allowed SWT classes is intended purely to enable those not on the SWT development team to implement patches in order to get around specific limitations in advance of when those limitations can be addressed by the team. Subclassing should not be attempted without an intimate and detailed understanding of the hierarchy.
checkSubclass
in class Widget
public Control getControl()
public DropTargetListener[] getDropListeners()
DropTargetListener
interface.SWTException
- DropTargetListener
,
addDropListener(org.eclipse.swt.dnd.DropTargetListener)
,
removeDropListener(org.eclipse.swt.dnd.DropTargetListener)
,
DropTargetEvent
public DropTargetEffect getDropTargetEffect()
public Transfer[] getTransfer()
public void removeDropListener(DropTargetListener listener)
listener
- the listener which should no longer be notifiedjava.lang.IllegalArgumentException
- SWTException
- DropTargetListener
,
addDropListener(org.eclipse.swt.dnd.DropTargetListener)
,
getDropListeners()
public void setDropTargetEffect(DropTargetEffect effect)
effect
- the drop effect that is registered for this DropTargetpublic void setTransfer(Transfer[] transferAgents)
transferAgents
- a list of Transfer objects which define the types of data that can be
dropped on this targetjava.lang.IllegalArgumentException
- public <T> T getAdapter(java.lang.Class<T> adapter)
Widget
Adaptable
interface.
IMPORTANT: This method is not part of the RWT public API. It is marked public only so that it can be shared within the packages provided by RWT. It should never be accessed from application code.
getAdapter
in interface Adaptable
getAdapter
in class Widget
adapter
- the lookup classnull
if
there is no adapter associated with the given class.
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All rights reserved. This program and the accompanying materials
are made available under the terms of the
Eclipse Public License v1.0