Class DelegatingDropAdapter
- java.lang.Object
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- org.eclipse.jface.util.DelegatingDropAdapter
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- All Implemented Interfaces:
EventListener,DropTargetListener,SWTEventListener
public class DelegatingDropAdapter extends Object implements DropTargetListener
ADelegatingDropAdapteris aDropTargetListenerthat maintains and delegates to a set ofTransferDropTargetListeners. EachTransferDropTargetListenercan then be implemented as if it were the DropTarget's onlyDropTargetListener.On
dragEnter,dragOperationChanged,dragOveranddrop, a current listener is obtained from the set of allTransferDropTargetListeners. The current listener is the first listener to returntrueforTransferDropTargetListener.isEnabled(DropTargetEvent). The current listener is forwarded allDropTargetEventsuntil some other listener becomes the current listener, or the drop terminates.After adding all
TransferDropTargetListenersto theDelegatingDropAdapterthe combined set ofTransfersshould be set in the SWTDropTarget.#getTransfers()provides the set ofTransfertypes of allTransferDropTargetListeners.The following example snippet shows a
DelegatingDropAdapterwith twoTransferDropTargetListeners. 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
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Constructor Summary
Constructors Constructor Description DelegatingDropAdapter()
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description voidaddDropTargetListener(TransferDropTargetListener listener)Adds the givenTransferDropTargetListener.voiddragEnter(DropTargetEvent event)The cursor has entered the drop target boundaries.voiddragLeave(DropTargetEvent event)The cursor has left the drop target boundaries.voiddragOperationChanged(DropTargetEvent event)The operation being performed has changed (usually due to the user changing a drag modifier key while dragging).voiddragOver(DropTargetEvent event)The cursor is moving over the drop target.voiddrop(DropTargetEvent event)Forwards this event to the current listener, if there is one.voiddropAccept(DropTargetEvent event)Forwards this event to the current listener if there is one.Transfer[]getTransfers()Returns the combined set ofTransfertypes of allTransferDropTargetListeners.booleanisEmpty()Returnstrueif there are no listeners to delegate events to.voidremoveDropTargetListener(TransferDropTargetListener listener)Removes the givenTransferDropTargetListener.
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Method Detail
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addDropTargetListener
public void addDropTargetListener(TransferDropTargetListener listener)
Adds the givenTransferDropTargetListener.- Parameters:
listener- the new listener
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dragEnter
public void dragEnter(DropTargetEvent event)
The cursor has entered the drop target boundaries. The current listener is updated, and#dragEnter()is forwarded to the current listener.- Specified by:
dragEnterin interfaceDropTargetListener- Parameters:
event- the drop target event- See Also:
DropTargetListener.dragEnter(DropTargetEvent)
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dragLeave
public void dragLeave(DropTargetEvent event)
The cursor has left the drop target boundaries. The event is forwarded to the current listener.- Specified by:
dragLeavein interfaceDropTargetListener- Parameters:
event- the drop target event- See Also:
DropTargetListener.dragLeave(DropTargetEvent)
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dragOperationChanged
public void dragOperationChanged(DropTargetEvent event)
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:
dragOperationChangedin interfaceDropTargetListener- Parameters:
event- the drop target event- See Also:
DropTargetListener.dragOperationChanged(DropTargetEvent)
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dragOver
public void dragOver(DropTargetEvent event)
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.detailfield is set toDND.DROP_NONEto indicate an invalid drop.- Specified by:
dragOverin interfaceDropTargetListener- Parameters:
event- the drop target event- See Also:
DropTargetListener.dragOver(DropTargetEvent)
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drop
public void drop(DropTargetEvent event)
Forwards this event to the current listener, if there is one. Sets the current listener tonullafterwards.- Specified by:
dropin interfaceDropTargetListener- Parameters:
event- the drop target event- See Also:
DropTargetListener.drop(DropTargetEvent)
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dropAccept
public void dropAccept(DropTargetEvent event)
Forwards this event to the current listener if there is one.- Specified by:
dropAcceptin interfaceDropTargetListener- Parameters:
event- the drop target event- See Also:
DropTargetListener.dropAccept(DropTargetEvent)
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getTransfers
public Transfer[] getTransfers()
Returns the combined set ofTransfertypes of allTransferDropTargetListeners.- Returns:
- the combined set of
Transfertypes
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isEmpty
public boolean isEmpty()
Returnstrueif there are no listeners to delegate events to.- Returns:
trueif there are noTransferDropTargetListenersfalseotherwise
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removeDropTargetListener
public void removeDropTargetListener(TransferDropTargetListener listener)
Removes the givenTransferDropTargetListener. Listeners should not be removed while a drag and drop operation is in progress.- Parameters:
listener- the listener to remove
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