Java example source code file (DragSourceDragEvent.java)

This example Java source code file (DragSourceDragEvent.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

awt, dragsourcedragevent, dragsourceevent, event, jdk_1_3_modifiers, jdk_1_4_modifiers

The DragSourceDragEvent.java Java example source code

/*
 * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
 * 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
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package java.awt.dnd;

import java.awt.event.InputEvent;

/**
 * The <code>DragSourceDragEvent is
 * delivered from the <code>DragSourceContextPeer,
 * via the <code>DragSourceContext, to the DragSourceListener
 * registered with that <code>DragSourceContext and with its associated
 * <code>DragSource.
 * <p>
 * The <code>DragSourceDragEvent reports the target drop action
 * and the <i>user drop action that reflect the current state of
 * the drag operation.
 * <p>
 * <i>Target drop action is one of DnDConstants that represents
 * the drop action selected by the current drop target if this drop action is
 * supported by the drag source or <code>DnDConstants.ACTION_NONE if this
 * drop action is not supported by the drag source.
 * <p>
 * <i>User drop action depends on the drop actions supported by the drag
 * source and the drop action selected by the user. The user can select a drop
 * action by pressing modifier keys during the drag operation:
 * <pre>
 *   Ctrl + Shift -> ACTION_LINK
 *   Ctrl         -> ACTION_COPY
 *   Shift        -> ACTION_MOVE
 * </pre>
 * If the user selects a drop action, the <i>user drop action is one of
 * <code>DnDConstants that represents the selected drop action if this
 * drop action is supported by the drag source or
 * <code>DnDConstants.ACTION_NONE if this drop action is not supported
 * by the drag source.
 * <p>
 * If the user doesn't select a drop action, the set of
 * <code>DnDConstants that represents the set of drop actions supported
 * by the drag source is searched for <code>DnDConstants.ACTION_MOVE,
 * then for <code>DnDConstants.ACTION_COPY, then for
 * <code>DnDConstants.ACTION_LINK and the user drop action is the
 * first constant found. If no constant is found the <i>user drop action
 * is <code>DnDConstants.ACTION_NONE.
 *
 * @since 1.2
 *
 */

public class DragSourceDragEvent extends DragSourceEvent {

    private static final long serialVersionUID = 481346297933902471L;

    /**
     * Constructs a <code>DragSourceDragEvent.
     * This class is typically
     * instantiated by the <code>DragSourceContextPeer
     * rather than directly
     * by client code.
     * The coordinates for this <code>DragSourceDragEvent
     * are not specified, so <code>getLocation will return
     * <code>null for this event.
     * <p>
     * The arguments <code>dropAction and action should
     * be one of <code>DnDConstants that represents a single action.
     * The argument <code>modifiers should be either a bitwise mask
     * of old <code>java.awt.event.InputEvent.*_MASK constants or a
     * bitwise mask of extended <code>java.awt.event.InputEvent.*_DOWN_MASK
     * constants.
     * This constructor does not throw any exception for invalid <code>dropAction,
     * <code>action and modifiers.
     *
     * @param dsc the <code>DragSourceContext that is to manage
     *            notifications for this event.
     * @param dropAction the user drop action.
     * @param action the target drop action.
     * @param modifiers the modifier keys down during event (shift, ctrl,
     *        alt, meta)
     *        Either extended _DOWN_MASK or old _MASK modifiers
     *        should be used, but both models should not be mixed
     *        in one event. Use of the extended modifiers is
     *        preferred.
     *
     * @throws IllegalArgumentException if <code>dsc is null.
     *
     * @see java.awt.event.InputEvent
     * @see DragSourceEvent#getLocation
     */

    public DragSourceDragEvent(DragSourceContext dsc, int dropAction,
                               int action, int modifiers) {
        super(dsc);

        targetActions    = action;
        gestureModifiers = modifiers;
        this.dropAction  = dropAction;
        if ((modifiers & ~(JDK_1_3_MODIFIERS | JDK_1_4_MODIFIERS)) != 0) {
            invalidModifiers = true;
        } else if ((getGestureModifiers() != 0) && (getGestureModifiersEx() == 0)) {
            setNewModifiers();
        } else if ((getGestureModifiers() == 0) && (getGestureModifiersEx() != 0)) {
            setOldModifiers();
        } else {
            invalidModifiers = true;
        }
    }

    /**
     * Constructs a <code>DragSourceDragEvent given the specified
     * <code>DragSourceContext, user drop action, target drop action,
     * modifiers and coordinates.
     * <p>
     * The arguments <code>dropAction and action should
     * be one of <code>DnDConstants that represents a single action.
     * The argument <code>modifiers should be either a bitwise mask
     * of old <code>java.awt.event.InputEvent.*_MASK constants or a
     * bitwise mask of extended <code>java.awt.event.InputEvent.*_DOWN_MASK
     * constants.
     * This constructor does not throw any exception for invalid <code>dropAction,
     * <code>action and modifiers.
     *
     * @param dsc the <code>DragSourceContext associated with this
     *        event.
     * @param dropAction the user drop action.
     * @param action the target drop action.
     * @param modifiers the modifier keys down during event (shift, ctrl,
     *        alt, meta)
     *        Either extended _DOWN_MASK or old _MASK modifiers
     *        should be used, but both models should not be mixed
     *        in one event. Use of the extended modifiers is
     *        preferred.
     * @param x   the horizontal coordinate for the cursor location
     * @param y   the vertical coordinate for the cursor location
     *
     * @throws IllegalArgumentException if <code>dsc is null.
     *
     * @see java.awt.event.InputEvent
     * @since 1.4
     */
    public DragSourceDragEvent(DragSourceContext dsc, int dropAction,
                               int action, int modifiers, int x, int y) {
        super(dsc, x, y);

        targetActions    = action;
        gestureModifiers = modifiers;
        this.dropAction  = dropAction;
        if ((modifiers & ~(JDK_1_3_MODIFIERS | JDK_1_4_MODIFIERS)) != 0) {
            invalidModifiers = true;
        } else if ((getGestureModifiers() != 0) && (getGestureModifiersEx() == 0)) {
            setNewModifiers();
        } else if ((getGestureModifiers() == 0) && (getGestureModifiersEx() != 0)) {
            setOldModifiers();
        } else {
            invalidModifiers = true;
        }
    }

    /**
     * This method returns the target drop action.
     *
     * @return the target drop action.
     */
    public int getTargetActions() {
        return targetActions;
    }


    private static final int JDK_1_3_MODIFIERS = InputEvent.SHIFT_DOWN_MASK - 1;
    private static final int JDK_1_4_MODIFIERS =
            ((InputEvent.ALT_GRAPH_DOWN_MASK << 1) - 1) & ~JDK_1_3_MODIFIERS;

    /**
     * This method returns an <code>int representing
     * the current state of the input device modifiers
     * associated with the user's gesture. Typically these
     * would be mouse buttons or keyboard modifiers.
     * <P>
     * If the <code>modifiers passed to the constructor
     * are invalid, this method returns them unchanged.
     *
     * @return the current state of the input device modifiers
     */

    public int getGestureModifiers() {
        return invalidModifiers ? gestureModifiers : gestureModifiers & JDK_1_3_MODIFIERS;
    }

    /**
     * This method returns an <code>int representing
     * the current state of the input device extended modifiers
     * associated with the user's gesture.
     * See {@link InputEvent#getModifiersEx}
     * <P>
     * If the <code>modifiers passed to the constructor
     * are invalid, this method returns them unchanged.
     *
     * @return the current state of the input device extended modifiers
     * @since 1.4
     */

    public int getGestureModifiersEx() {
        return invalidModifiers ? gestureModifiers : gestureModifiers & JDK_1_4_MODIFIERS;
    }

    /**
     * This method returns the user drop action.
     *
     * @return the user drop action.
     */
    public int getUserAction() { return dropAction; }

    /**
     * This method returns the logical intersection of
     * the target drop action and the set of drop actions supported by
     * the drag source.
     *
     * @return the logical intersection of the target drop action and
     *         the set of drop actions supported by the drag source.
     */
    public int getDropAction() {
        return targetActions & getDragSourceContext().getSourceActions();
    }

    /*
     * fields
     */

    /**
     * The target drop action.
     *
     * @serial
     */
    private int     targetActions    = DnDConstants.ACTION_NONE;

    /**
     * The user drop action.
     *
     * @serial
     */
    private int     dropAction       = DnDConstants.ACTION_NONE;

    /**
     * The state of the input device modifiers associated with the user
     * gesture.
     *
     * @serial
     */
    private int     gestureModifiers = 0;

    /**
     * Indicates whether the <code>gestureModifiers are invalid.
     *
     * @serial
     */
    private boolean invalidModifiers;

    /**
     * Sets new modifiers by the old ones.
     * The mouse modifiers have higher priority than overlaying key
     * modifiers.
     */
    private void setNewModifiers() {
        if ((gestureModifiers & InputEvent.BUTTON1_MASK) != 0) {
            gestureModifiers |= InputEvent.BUTTON1_DOWN_MASK;
        }
        if ((gestureModifiers & InputEvent.BUTTON2_MASK) != 0) {
            gestureModifiers |= InputEvent.BUTTON2_DOWN_MASK;
        }
        if ((gestureModifiers & InputEvent.BUTTON3_MASK) != 0) {
            gestureModifiers |= InputEvent.BUTTON3_DOWN_MASK;
        }
        if ((gestureModifiers & InputEvent.SHIFT_MASK) != 0) {
            gestureModifiers |= InputEvent.SHIFT_DOWN_MASK;
        }
        if ((gestureModifiers & InputEvent.CTRL_MASK) != 0) {
            gestureModifiers |= InputEvent.CTRL_DOWN_MASK;
        }
        if ((gestureModifiers & InputEvent.ALT_GRAPH_MASK) != 0) {
            gestureModifiers |= InputEvent.ALT_GRAPH_DOWN_MASK;
        }
    }

    /**
     * Sets old modifiers by the new ones.
     */
    private void setOldModifiers() {
        if ((gestureModifiers & InputEvent.BUTTON1_DOWN_MASK) != 0) {
            gestureModifiers |= InputEvent.BUTTON1_MASK;
        }
        if ((gestureModifiers & InputEvent.BUTTON2_DOWN_MASK) != 0) {
            gestureModifiers |= InputEvent.BUTTON2_MASK;
        }
        if ((gestureModifiers & InputEvent.BUTTON3_DOWN_MASK) != 0) {
            gestureModifiers |= InputEvent.BUTTON3_MASK;
        }
        if ((gestureModifiers & InputEvent.SHIFT_DOWN_MASK) != 0) {
            gestureModifiers |= InputEvent.SHIFT_MASK;
        }
        if ((gestureModifiers & InputEvent.CTRL_DOWN_MASK) != 0) {
            gestureModifiers |= InputEvent.CTRL_MASK;
        }
        if ((gestureModifiers & InputEvent.ALT_GRAPH_DOWN_MASK) != 0) {
            gestureModifiers |= InputEvent.ALT_GRAPH_MASK;
        }
    }
}