Java example source code file (DropTargetListener.java)

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Java - Java tags/keywords

awt, dnd, drag, drop, droptargetlistener, eventlistener, util

The DropTargetListener.java Java example source code

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package java.awt.dnd;

import java.util.EventListener;

import java.awt.dnd.DropTargetDragEvent;
import java.awt.dnd.DropTargetDropEvent;

/**
 * The <code>DropTargetListener interface
 * is the callback interface used by the
 * <code>DropTarget class to provide
 * notification of DnD operations that involve
 * the subject <code>DropTarget. Methods of
 * this interface may be implemented to provide
 * "drag under" visual feedback to the user throughout
 * the Drag and Drop operation.
 * <p>
 * Create a listener object by implementing the interface and then register it
 * with a <code>DropTarget. When the drag enters, moves over, or exits
 * the operable part of the drop site for that <code>DropTarget, when
 * the drop action changes, and when the drop occurs, the relevant method in
 * the listener object is invoked, and the <code>DropTargetEvent is
 * passed to it.
 * <p>
 * The operable part of the drop site for the <code>DropTarget is
 * the part of the associated <code>Component's geometry that is not
 * obscured by an overlapping top-level window or by another
 * <code>Component higher in the Z-order that has an associated active
 * <code>DropTarget.
 * <p>
 * During the drag, the data associated with the current drag operation can be
 * retrieved by calling <code>getTransferable() on
 * <code>DropTargetDragEvent instances passed to the listener's
 * methods.
 * <p>
 * Note that <code>getTransferable() on the
 * <code>DropTargetDragEvent instance should only be called within the
 * respective listener's method and all the necessary data should be retrieved
 * from the returned <code>Transferable before that method returns.
 *
 * @since 1.2
 */

public interface DropTargetListener extends EventListener {

    /**
     * Called while a drag operation is ongoing, when the mouse pointer enters
     * the operable part of the drop site for the <code>DropTarget
     * registered with this listener.
     *
     * @param dtde the <code>DropTargetDragEvent
     */

    void dragEnter(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 <code>DropTarget
     * registered with this listener.
     *
     * @param dtde the <code>DropTargetDragEvent
     */

    void dragOver(DropTargetDragEvent dtde);

    /**
     * Called if the user has modified
     * the current drop gesture.
     * <P>
     * @param dtde the <code>DropTargetDragEvent
     */

    void dropActionChanged(DropTargetDragEvent dtde);

    /**
     * Called while a drag operation is ongoing, when the mouse pointer has
     * exited the operable part of the drop site for the
     * <code>DropTarget registered with this listener.
     *
     * @param dte the <code>DropTargetEvent
     */

    void dragExit(DropTargetEvent dte);

    /**
     * Called when the drag operation has terminated with a drop on
     * the operable part of the drop site for the <code>DropTarget
     * registered with this listener.
     * <p>
     * This method is responsible for undertaking
     * the transfer of the data associated with the
     * gesture. The <code>DropTargetDropEvent
     * provides a means to obtain a <code>Transferable
     * object that represents the data object(s) to
     * be transfered.<P>
     * From this method, the <code>DropTargetListener
     * shall accept or reject the drop via the
     * acceptDrop(int dropAction) or rejectDrop() methods of the
     * <code>DropTargetDropEvent parameter.
     * <P>
     * Subsequent to acceptDrop(), but not before,
     * <code>DropTargetDropEvent's getTransferable()
     * method may be invoked, and data transfer may be
     * performed via the returned <code>Transferable's
     * getTransferData() method.
     * <P>
     * 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
     * <code>boolean to the DropTargetDropEvent's
     * dropComplete(boolean success) method.
     * <P>
     * Note: The data transfer should be completed before the call  to the
     * <code>DropTargetDropEvent's dropComplete(boolean success) method.
     * After that, a call to the getTransferData() method of the
     * <code>Transferable returned by
     * <code>DropTargetDropEvent.getTransferable() is guaranteed to
     * succeed only if the data transfer is local; that is, only if
     * <code>DropTargetDropEvent.isLocalTransfer() returns
     * <code>true. Otherwise, the behavior of the call is
     * implementation-dependent.
     * <P>
     * @param dtde the <code>DropTargetDropEvent
     */

    void drop(DropTargetDropEvent dtde);
}