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675 lines
24 KiB
Java
675 lines
24 KiB
Java
/*
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* Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.awt.dnd;
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import java.awt.AWTError;
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import java.awt.Component;
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import java.awt.Cursor;
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import java.awt.Image;
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import java.awt.Point;
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import java.awt.Toolkit;
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import java.awt.datatransfer.DataFlavor;
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import java.awt.datatransfer.Transferable;
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import java.awt.datatransfer.UnsupportedFlavorException;
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import java.awt.dnd.peer.DragSourceContextPeer;
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import java.io.IOException;
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import java.io.InvalidObjectException;
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import java.io.ObjectInputStream;
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import java.io.ObjectOutputStream;
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import java.io.Serializable;
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import java.util.TooManyListenersException;
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import sun.awt.AWTAccessor;
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import sun.awt.ComponentFactory;
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/**
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* The {@code DragSourceContext} class is responsible for managing the
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* initiator side of the Drag and Drop protocol. In particular, it is responsible
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* for managing drag event notifications to the
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* {@linkplain DragSourceListener DragSourceListeners}
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* and {@linkplain DragSourceMotionListener DragSourceMotionListeners}, and providing the
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* {@link Transferable} representing the source data for the drag operation.
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* <p>
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* Note that the {@code DragSourceContext} itself
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* implements the {@code DragSourceListener} and
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* {@code DragSourceMotionListener} interfaces.
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* This is to allow the platform peer
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* (the {@link DragSourceContextPeer} instance)
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* created by the {@link DragSource} to notify
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* the {@code DragSourceContext} of
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* state changes in the ongoing operation. This allows the
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* {@code DragSourceContext} object to interpose
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* itself between the platform and the
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* listeners provided by the initiator of the drag operation.
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* <p>
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* <a id="defaultCursor"></a>
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* By default, {@code DragSourceContext} sets the cursor as appropriate
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* for the current state of the drag and drop operation. For example, if
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* the user has chosen {@linkplain DnDConstants#ACTION_MOVE the move action},
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* and the pointer is over a target that accepts
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* the move action, the default move cursor is shown. When
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* the pointer is over an area that does not accept the transfer,
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* the default "no drop" cursor is shown.
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* <p>
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* This default handling mechanism is disabled when a custom cursor is set
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* by the {@link #setCursor} method. When the default handling is disabled,
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* it becomes the responsibility
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* of the developer to keep the cursor up to date, by listening
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* to the {@code DragSource} events and calling the {@code setCursor()} method.
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* Alternatively, you can provide custom cursor behavior by providing
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* custom implementations of the {@code DragSource}
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* and the {@code DragSourceContext} classes.
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*
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* @see DragSourceListener
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* @see DragSourceMotionListener
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* @see DnDConstants
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* @since 1.2
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*/
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public class DragSourceContext
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implements DragSourceListener, DragSourceMotionListener, Serializable {
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private static final long serialVersionUID = -115407898692194719L;
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// used by updateCurrentCursor
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/**
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* An {@code int} used by updateCurrentCursor()
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* indicating that the {@code Cursor} should change
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* to the default (no drop) {@code Cursor}.
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*/
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protected static final int DEFAULT = 0;
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/**
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* An {@code int} used by updateCurrentCursor()
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* indicating that the {@code Cursor}
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* has entered a {@code DropTarget}.
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*/
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protected static final int ENTER = 1;
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/**
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* An {@code int} used by updateCurrentCursor()
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* indicating that the {@code Cursor} is
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* over a {@code DropTarget}.
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*/
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protected static final int OVER = 2;
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/**
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* An {@code int} used by updateCurrentCursor()
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* indicating that the user operation has changed.
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*/
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protected static final int CHANGED = 3;
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static {
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AWTAccessor.setDragSourceContextAccessor(dsc -> dsc.peer);
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}
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/**
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* Called from {@code DragSource}, this constructor creates a new
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* {@code DragSourceContext} given the
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* {@code DragSourceContextPeer} for this Drag, the
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* {@code DragGestureEvent} that triggered the Drag, the initial
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* {@code Cursor} to use for the Drag, an (optional)
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* {@code Image} to display while the Drag is taking place, the offset
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* of the {@code Image} origin from the hotspot at the instant of the
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* triggering event, the {@code Transferable} subject data, and the
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* {@code DragSourceListener} to use during the Drag and Drop
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* operation.
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* <br>
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* If {@code DragSourceContextPeer} is {@code null}
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* {@code NullPointerException} is thrown.
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* <br>
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* If {@code DragGestureEvent} is {@code null}
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* {@code NullPointerException} is thrown.
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* <br>
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* If {@code Cursor} is {@code null} no exception is thrown and
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* the default drag cursor behavior is activated for this drag operation.
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* <br>
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* If {@code Image} is {@code null} no exception is thrown.
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* <br>
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* If {@code Image} is not {@code null} and the offset is
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* {@code null NullPointerException} is thrown.
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* <br>
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* If {@code Transferable} is {@code null}
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* {@code NullPointerException} is thrown.
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* <br>
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* If {@code DragSourceListener} is {@code null} no exception
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* is thrown.
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*
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* @param trigger the triggering event
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* @param dragCursor the initial {@code Cursor} for this drag operation
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* or {@code null} for the default cursor handling;
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* see <a href="DragSourceContext.html#defaultCursor">class level documentation</a>
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* for more details on the cursor handling mechanism during drag and drop
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* @param dragImage the {@code Image} to drag (or {@code null})
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* @param offset the offset of the image origin from the hotspot at the
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* instant of the triggering event
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* @param t the {@code Transferable}
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* @param dsl the {@code DragSourceListener}
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*
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* @throws IllegalArgumentException if the {@code Component} associated
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* with the trigger event is {@code null}.
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* @throws IllegalArgumentException if the {@code DragSource} for the
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* trigger event is {@code null}.
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* @throws IllegalArgumentException if the drag action for the
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* trigger event is {@code DnDConstants.ACTION_NONE}.
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* @throws IllegalArgumentException if the source actions for the
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* {@code DragGestureRecognizer} associated with the trigger
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* event are equal to {@code DnDConstants.ACTION_NONE}.
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* @throws NullPointerException if dscp, trigger, or t are null, or
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* if dragImage is non-null and offset is null
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*/
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public DragSourceContext(DragGestureEvent trigger, Cursor dragCursor,
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Image dragImage, Point offset, Transferable t,
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DragSourceListener dsl) {
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Toolkit toolkit = Toolkit.getDefaultToolkit();
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if (!(toolkit instanceof ComponentFactory)) {
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throw new AWTError("Unsupported toolkit: " + toolkit);
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}
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DragSourceContextPeer dscp = ((ComponentFactory) toolkit).
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createDragSourceContextPeer(trigger);
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if (dscp == null) {
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throw new NullPointerException("DragSourceContextPeer");
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}
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if (trigger == null) {
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throw new NullPointerException("Trigger");
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}
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if (trigger.getDragSource() == null) {
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throw new IllegalArgumentException("DragSource");
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}
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if (trigger.getComponent() == null) {
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throw new IllegalArgumentException("Component");
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}
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if (trigger.getSourceAsDragGestureRecognizer().getSourceActions() ==
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DnDConstants.ACTION_NONE) {
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throw new IllegalArgumentException("source actions");
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}
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if (trigger.getDragAction() == DnDConstants.ACTION_NONE) {
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throw new IllegalArgumentException("no drag action");
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}
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if (t == null) {
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throw new NullPointerException("Transferable");
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}
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if (dragImage != null && offset == null) {
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throw new NullPointerException("offset");
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}
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peer = dscp;
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this.trigger = trigger;
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cursor = dragCursor;
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transferable = t;
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listener = dsl;
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sourceActions =
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trigger.getSourceAsDragGestureRecognizer().getSourceActions();
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useCustomCursor = (dragCursor != null);
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updateCurrentCursor(trigger.getDragAction(), getSourceActions(), DEFAULT);
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}
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/**
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* Returns the {@code DragSource}
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* that instantiated this {@code DragSourceContext}.
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*
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* @return the {@code DragSource} that
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* instantiated this {@code DragSourceContext}
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*/
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public DragSource getDragSource() { return trigger.getDragSource(); }
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/**
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* Returns the {@code Component} associated with this
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* {@code DragSourceContext}.
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*
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* @return the {@code Component} that started the drag
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*/
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public Component getComponent() { return trigger.getComponent(); }
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/**
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* Returns the {@code DragGestureEvent}
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* that initially triggered the drag.
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*
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* @return the Event that triggered the drag
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*/
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public DragGestureEvent getTrigger() { return trigger; }
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/**
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* Returns a bitwise mask of {@code DnDConstants} that
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* represent the set of drop actions supported by the drag source for the
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* drag operation associated with this {@code DragSourceContext}.
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*
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* @return the drop actions supported by the drag source
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*/
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public int getSourceActions() {
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return sourceActions;
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}
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/**
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* Sets the custom cursor for this drag operation to the specified
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* {@code Cursor}. If the specified {@code Cursor}
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* is {@code null}, the default drag cursor behavior is
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* activated for this drag operation, otherwise it is deactivated.
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*
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* @param c the initial {@code Cursor} for this drag operation,
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* or {@code null} for the default cursor handling;
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* see {@linkplain Cursor class
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* level documentation} for more details
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* on the cursor handling during drag and drop
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*
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*/
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public synchronized void setCursor(Cursor c) {
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useCustomCursor = (c != null);
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setCursorImpl(c);
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}
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/**
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* Returns the current custom drag {@code Cursor}.
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*
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* @return the current custom drag {@code Cursor}, if it was set
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* otherwise returns {@code null}.
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* @see #setCursor
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*/
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public Cursor getCursor() { return cursor; }
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/**
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* Add a {@code DragSourceListener} to this
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* {@code DragSourceContext} if one has not already been added.
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* If a {@code DragSourceListener} already exists,
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* this method throws a {@code TooManyListenersException}.
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*
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* @param dsl the {@code DragSourceListener} to add.
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* Note that while {@code null} is not prohibited,
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* it is not acceptable as a parameter.
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*
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* @throws TooManyListenersException if
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* a {@code DragSourceListener} has already been added
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*/
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public synchronized void addDragSourceListener(DragSourceListener dsl) throws TooManyListenersException {
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if (dsl == null) return;
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if (equals(dsl)) throw new IllegalArgumentException("DragSourceContext may not be its own listener");
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if (listener != null)
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throw new TooManyListenersException();
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else
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listener = dsl;
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}
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/**
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* Removes the specified {@code DragSourceListener}
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* from this {@code DragSourceContext}.
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*
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* @param dsl the {@code DragSourceListener} to remove;
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* note that while {@code null} is not prohibited,
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* it is not acceptable as a parameter
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*/
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public synchronized void removeDragSourceListener(DragSourceListener dsl) {
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if (listener != null && listener.equals(dsl)) {
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listener = null;
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} else
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throw new IllegalArgumentException();
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}
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/**
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* Notifies the peer that the {@code Transferable}'s
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* {@code DataFlavor}s have changed.
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*/
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public void transferablesFlavorsChanged() {
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if (peer != null) peer.transferablesFlavorsChanged();
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}
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/**
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* Calls {@code dragEnter} on the
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* {@code DragSourceListener}s registered with this
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* {@code DragSourceContext} and with the associated
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* {@code DragSource}, and passes them the specified
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* {@code DragSourceDragEvent}.
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*
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* @param dsde the {@code DragSourceDragEvent}
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*/
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public void dragEnter(DragSourceDragEvent dsde) {
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DragSourceListener dsl = listener;
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if (dsl != null) {
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dsl.dragEnter(dsde);
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}
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getDragSource().processDragEnter(dsde);
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updateCurrentCursor(getSourceActions(), dsde.getTargetActions(), ENTER);
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}
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/**
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* Calls {@code dragOver} on the
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* {@code DragSourceListener}s registered with this
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* {@code DragSourceContext} and with the associated
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* {@code DragSource}, and passes them the specified
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* {@code DragSourceDragEvent}.
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*
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* @param dsde the {@code DragSourceDragEvent}
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*/
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public void dragOver(DragSourceDragEvent dsde) {
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DragSourceListener dsl = listener;
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if (dsl != null) {
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dsl.dragOver(dsde);
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}
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getDragSource().processDragOver(dsde);
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updateCurrentCursor(getSourceActions(), dsde.getTargetActions(), OVER);
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}
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/**
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* Calls {@code dragExit} on the
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* {@code DragSourceListener}s registered with this
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* {@code DragSourceContext} and with the associated
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* {@code DragSource}, and passes them the specified
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* {@code DragSourceEvent}.
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*
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* @param dse the {@code DragSourceEvent}
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*/
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public void dragExit(DragSourceEvent dse) {
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DragSourceListener dsl = listener;
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if (dsl != null) {
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dsl.dragExit(dse);
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}
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getDragSource().processDragExit(dse);
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updateCurrentCursor(DnDConstants.ACTION_NONE, DnDConstants.ACTION_NONE, DEFAULT);
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}
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/**
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* Calls {@code dropActionChanged} on the
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* {@code DragSourceListener}s registered with this
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* {@code DragSourceContext} and with the associated
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* {@code DragSource}, and passes them the specified
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* {@code DragSourceDragEvent}.
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*
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* @param dsde the {@code DragSourceDragEvent}
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*/
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public void dropActionChanged(DragSourceDragEvent dsde) {
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DragSourceListener dsl = listener;
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if (dsl != null) {
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dsl.dropActionChanged(dsde);
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}
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getDragSource().processDropActionChanged(dsde);
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updateCurrentCursor(getSourceActions(), dsde.getTargetActions(), CHANGED);
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}
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/**
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* Calls {@code dragDropEnd} on the
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* {@code DragSourceListener}s registered with this
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* {@code DragSourceContext} and with the associated
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* {@code DragSource}, and passes them the specified
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* {@code DragSourceDropEvent}.
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*
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* @param dsde the {@code DragSourceDropEvent}
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*/
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public void dragDropEnd(DragSourceDropEvent dsde) {
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DragSourceListener dsl = listener;
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if (dsl != null) {
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dsl.dragDropEnd(dsde);
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}
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getDragSource().processDragDropEnd(dsde);
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}
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/**
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* Calls {@code dragMouseMoved} on the
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* {@code DragSourceMotionListener}s registered with the
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* {@code DragSource} associated with this
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* {@code DragSourceContext}, and them passes the specified
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* {@code DragSourceDragEvent}.
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*
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* @param dsde the {@code DragSourceDragEvent}
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* @since 1.4
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*/
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public void dragMouseMoved(DragSourceDragEvent dsde) {
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getDragSource().processDragMouseMoved(dsde);
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}
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/**
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* Returns the {@code Transferable} associated with
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* this {@code DragSourceContext}.
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*
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* @return the {@code Transferable}
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*/
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public Transferable getTransferable() { return transferable; }
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/**
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* If the default drag cursor behavior is active, this method
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* sets the default drag cursor for the specified actions
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* supported by the drag source, the drop target action,
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* and status, otherwise this method does nothing.
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*
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* @param sourceAct the actions supported by the drag source
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* @param targetAct the drop target action
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* @param status one of the fields {@code DEFAULT},
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* {@code ENTER}, {@code OVER},
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* {@code CHANGED}
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*/
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@SuppressWarnings("fallthrough")
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protected synchronized void updateCurrentCursor(int sourceAct, int targetAct, int status) {
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// if the cursor has been previously set then don't do any defaults
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// processing.
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if (useCustomCursor) {
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return;
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}
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// do defaults processing
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Cursor c = null;
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switch (status) {
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default:
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targetAct = DnDConstants.ACTION_NONE;
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case ENTER:
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case OVER:
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case CHANGED:
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int ra = sourceAct & targetAct;
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if (ra == DnDConstants.ACTION_NONE) { // no drop possible
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if ((sourceAct & DnDConstants.ACTION_LINK) == DnDConstants.ACTION_LINK)
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c = DragSource.DefaultLinkNoDrop;
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else if ((sourceAct & DnDConstants.ACTION_MOVE) == DnDConstants.ACTION_MOVE)
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c = DragSource.DefaultMoveNoDrop;
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else
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c = DragSource.DefaultCopyNoDrop;
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} else { // drop possible
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if ((ra & DnDConstants.ACTION_LINK) == DnDConstants.ACTION_LINK)
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c = DragSource.DefaultLinkDrop;
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else if ((ra & DnDConstants.ACTION_MOVE) == DnDConstants.ACTION_MOVE)
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c = DragSource.DefaultMoveDrop;
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else
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c = DragSource.DefaultCopyDrop;
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}
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}
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setCursorImpl(c);
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}
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private void setCursorImpl(Cursor c) {
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|
if (cursor == null || !cursor.equals(c)) {
|
|
cursor = c;
|
|
if (peer != null) peer.setCursor(cursor);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Serializes this {@code DragSourceContext}. This method first
|
|
* performs default serialization. Next, this object's
|
|
* {@code Transferable} is written out if and only if it can be
|
|
* serialized. If not, {@code null} is written instead. In this case,
|
|
* a {@code DragSourceContext} created from the resulting deserialized
|
|
* stream will contain a dummy {@code Transferable} which supports no
|
|
* {@code DataFlavor}s. Finally, this object's
|
|
* {@code DragSourceListener} is written out if and only if it can be
|
|
* serialized. If not, {@code null} is written instead.
|
|
*
|
|
* @serialData The default serializable fields, in alphabetical order,
|
|
* followed by either a {@code Transferable} instance, or
|
|
* {@code null}, followed by either a
|
|
* {@code DragSourceListener} instance, or
|
|
* {@code null}.
|
|
* @since 1.4
|
|
*/
|
|
private void writeObject(ObjectOutputStream s) throws IOException {
|
|
s.defaultWriteObject();
|
|
|
|
s.writeObject(SerializationTester.test(transferable)
|
|
? transferable : null);
|
|
s.writeObject(SerializationTester.test(listener)
|
|
? listener : null);
|
|
}
|
|
|
|
/**
|
|
* Deserializes this {@code DragSourceContext}. This method first
|
|
* performs default deserialization for all non-{@code transient}
|
|
* fields. This object's {@code Transferable} and
|
|
* {@code DragSourceListener} are then deserialized as well by using
|
|
* the next two objects in the stream. If the resulting
|
|
* {@code Transferable} is {@code null}, this object's
|
|
* {@code Transferable} is set to a dummy {@code Transferable}
|
|
* which supports no {@code DataFlavor}s.
|
|
*
|
|
* @since 1.4
|
|
*/
|
|
private void readObject(ObjectInputStream s)
|
|
throws ClassNotFoundException, IOException
|
|
{
|
|
ObjectInputStream.GetField f = s.readFields();
|
|
|
|
DragGestureEvent newTrigger = (DragGestureEvent)f.get("trigger", null);
|
|
if (newTrigger == null) {
|
|
throw new InvalidObjectException("Null trigger");
|
|
}
|
|
if (newTrigger.getDragSource() == null) {
|
|
throw new InvalidObjectException("Null DragSource");
|
|
}
|
|
if (newTrigger.getComponent() == null) {
|
|
throw new InvalidObjectException("Null trigger component");
|
|
}
|
|
|
|
int newSourceActions = f.get("sourceActions", 0)
|
|
& (DnDConstants.ACTION_COPY_OR_MOVE | DnDConstants.ACTION_LINK);
|
|
if (newSourceActions == DnDConstants.ACTION_NONE) {
|
|
throw new InvalidObjectException("Invalid source actions");
|
|
}
|
|
int triggerActions = newTrigger.getDragAction();
|
|
if (triggerActions != DnDConstants.ACTION_COPY &&
|
|
triggerActions != DnDConstants.ACTION_MOVE &&
|
|
triggerActions != DnDConstants.ACTION_LINK) {
|
|
throw new InvalidObjectException("No drag action");
|
|
}
|
|
trigger = newTrigger;
|
|
|
|
cursor = (Cursor)f.get("cursor", null);
|
|
useCustomCursor = f.get("useCustomCursor", false);
|
|
sourceActions = newSourceActions;
|
|
|
|
transferable = (Transferable)s.readObject();
|
|
listener = (DragSourceListener)s.readObject();
|
|
|
|
// Implementation assumes 'transferable' is never null.
|
|
if (transferable == null) {
|
|
if (emptyTransferable == null) {
|
|
emptyTransferable = new Transferable() {
|
|
public DataFlavor[] getTransferDataFlavors() {
|
|
return new DataFlavor[0];
|
|
}
|
|
public boolean isDataFlavorSupported(DataFlavor flavor)
|
|
{
|
|
return false;
|
|
}
|
|
public Object getTransferData(DataFlavor flavor)
|
|
throws UnsupportedFlavorException
|
|
{
|
|
throw new UnsupportedFlavorException(flavor);
|
|
}
|
|
};
|
|
}
|
|
transferable = emptyTransferable;
|
|
}
|
|
}
|
|
|
|
private static Transferable emptyTransferable;
|
|
|
|
/*
|
|
* fields
|
|
*/
|
|
private final transient DragSourceContextPeer peer;
|
|
|
|
/**
|
|
* The event which triggered the start of the drag.
|
|
*
|
|
* @serial
|
|
*/
|
|
private DragGestureEvent trigger;
|
|
|
|
/**
|
|
* The current drag cursor.
|
|
*
|
|
* @serial
|
|
*/
|
|
private Cursor cursor;
|
|
|
|
private transient Transferable transferable;
|
|
|
|
private transient DragSourceListener listener;
|
|
|
|
/**
|
|
* {@code true} if the custom drag cursor is used instead of the
|
|
* default one.
|
|
*
|
|
* @serial
|
|
*/
|
|
private boolean useCustomCursor;
|
|
|
|
/**
|
|
* A bitwise mask of {@code DnDConstants} that represents the set of
|
|
* drop actions supported by the drag source for the drag operation associated
|
|
* with this {@code DragSourceContext.}
|
|
*
|
|
* @serial
|
|
*/
|
|
private int sourceActions;
|
|
}
|