DropTargetListener (Java 2 Platform SE v1.4.1) - JDK 5 Documentation v1.4.1, Java 2 SDK 英文文档

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Java^TM 2 Platform
Std. Ed. v1.4.1

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java.awt.dnd
Interface DropTargetListener

All Superinterfaces:: EventListener

All Known Implementing Classes:: DropTarget, DropTargetAdapter

public interface DropTargetListener
extends EventListener

The DropTargetListener interface is the callback interface used by the DropTarget class to provide notification of DnD operations that involve the subject DropTarget. Methods of this interface may be implemented to provide "drag under" visual feedback to the user throughout the Drag and Drop operation.

Create a listener object by implementing the interface and then register it with a DropTarget. When the drag enters, moves over, or exits the operable part of the drop site for that DropTarget, when the drop action changes, and when the drop occurs, the relevant method in the listener object is invoked, and the DropTargetEvent is passed to it.

The operable part of the drop site for the DropTarget is the part of the associated Component's geometry that is not obscured by an overlapping top-level window or by another Component higher in the Z-order that has an associated active DropTarget.

Since:: 1.2

Method Summary

void dragEnter(DropTargetDragEvent dtde)
          Called while a drag operation is ongoing, when the mouse pointer enters the operable part of the drop site for the DropTarget registered with this listener.

void dragExit(DropTargetEvent dte)
          Called while a drag operation is ongoing, when the mouse pointer has exited the operable part of the drop site for the DropTarget registered with this listener.

void dragOver(DropTargetDragEvent dtde)
          Called when a drag operation is ongoing, while the mouse pointer is still over the operable part of the drop site for the DropTarget registered with this listener.

void drop(DropTargetDropEvent dtde)
          Called when the drag operation has terminated with a drop on the operable part of the drop site for the DropTarget registered with this listener.

void dropActionChanged(DropTargetDragEvent dtde)
          Called if the user has modified the current drop gesture.

Method Detail

dragEnter

public void dragEnter(DropTargetDragEvent dtde)

Called while a drag operation is ongoing, when the mouse pointer enters the operable part of the drop site for the DropTarget registered with this listener.

Parameters:: dtde - the DropTargetDragEvent

dragOver

public void dragOver(DropTargetDragEvent dtde)

Called when a drag operation is ongoing, while the mouse pointer is still over the operable part of the drop site for the DropTarget registered with this listener.

Parameters:: dtde - the DropTargetDragEvent

dropActionChanged

public void dropActionChanged(DropTargetDragEvent dtde)

Called if the user has modified the current drop gesture.

Parameters:: dtde - the DropTargetDragEvent

dragExit

public void dragExit(DropTargetEvent dte)

Called while a drag operation is ongoing, when the mouse pointer has exited the operable part of the drop site for the DropTarget registered with this listener.

Parameters:: dte - the DropTargetEvent

drop

public void drop(DropTargetDropEvent dtde)

Called when the drag operation has terminated with a drop on the operable part of the drop site for the DropTarget registered with this listener.

This method is responsible for undertaking the transfer of the data associated with the gesture. The DropTargetDropEvent provides a means to obtain a Transferable object that represents the data object(s) to be transfered.

From this method, the DropTargetListener shall accept or reject the drop via the acceptDrop(int dropAction) or rejectDrop() methods of the DropTargetDropEvent parameter.

Subsequent to acceptDrop(), but not before, DropTargetDropEvent's getTransferable() method may be invoked, and data transfer may be performed via the returned Transferable's getTransferData() method.

At the completion of a drop, an implementation of this method is required to signal the success/failure of the drop by passing an appropriate boolean to the DropTargetDropEvent's dropComplete(boolean success) method.

Note: The data transfer should be completed before the call to the DropTargetDropEvent's dropComplete(boolean success) method. After that, a call to the getTransferData() method of the Transferable returned by DropTargetDropEvent.getTransferable() is guaranteed to succeed only if the data transfer is local; that is, only if DropTargetDropEvent.isLocalTransfer() returns true. Otherwise, the behavior of the call is implementation-dependent.

Parameters:: dtde - the DropTargetDropEvent