Java 1.2 How-To/JavaHowTo.iso/3rdParty/jbuilder/unsupported/JDK1.2beta3/SOURCE/SRC.ZIP/java/awt/dnd/DragSource.java

Java Source | 1998-03-20 | 5.6 KB | 198 lines

/*
 * @(#)DragSource.java    1.12 98/03/18
 *
 * Copyright 1997, 1998 by Sun Microsystems, Inc.,
 * 901 San Antonio Road, Palo Alto, California, 94303, U.S.A.
 * All rights reserved.
 *
 * This software is the confidential and proprietary information
 * of Sun Microsystems, Inc. ("Confidential Information").  You
 * shall not disclose such Confidential Information and shall use
 * it only in accordance with the terms of the license agreement
 * you entered into with Sun.
 */

package java.awt.dnd;

import java.awt.AWTError;
import java.awt.AWTException;
import java.awt.AWTEvent;
import java.awt.AWTPermission;
import java.awt.Component;
import java.awt.Cursor;
import java.awt.Image;
import java.awt.Point;
import java.awt.Toolkit;

import java.awt.datatransfer.Transferable;

import java.awt.dnd.DnDConstants;
import java.awt.dnd.DragSourceContext;
import java.awt.dnd.DragSourceListener;
import java.awt.dnd.FlavorMap;
import java.awt.dnd.SystemFlavorMap;
import java.awt.dnd.InvalidDnDOperationException;

import java.awt.dnd.peer.DragSourceContextPeer;

import java.security.AccessController;

/**
 * <p>
 * The DragSource class is a small class responsible for originating a
 * Drag and Drop operation.
 * </p>
 *
 * @version 1.12
 * @since JDK1.2
 *
 */

public class DragSource {

    /*
     * load a default cursor
     */

    private static Cursor load(String name) {
    try {
        return (Cursor)Toolkit.getDefaultToolkit().getDesktopProperty(name);
    } catch (Exception e) {
        e.printStackTrace();

        throw new RuntimeException("failed to load system cursor: " + name + " : " + e.getMessage());
    }
    }

    /**
     * Default Cursor Constants
     */

    public static final Cursor DefaultCopyDrop = load("DnD.Cursor.CopyDrop");
    public static final Cursor DefaultMoveDrop = load("DnD.Cursor.MoveDrop");
    public static final Cursor DefaultLinkDrop = load("DnD.Cursor.LinkDrop");

    public static final Cursor DefaultCopyNoDrop = load("DnD.Cursor.CopyNoDrop");
    public static final Cursor DefaultMoveNoDrop = load("DnD.Cursor.MoveNoDrop");
    public static final Cursor DefaultLinkNoDrop = load("DnD.Cursor.LinkNoDrop");

    /*
     * The System FlavorMap
     */

    private static final FlavorMap flavorMap = SystemFlavorMap.getDefaultFlavorMap();

    private static DragSource dflt;

    /**
     * @return the platform DragSource
     */

    public static DragSource getDefaultDragSource() {
    if (dflt == null) dflt = new DragSource();

    return dflt;
    }

    /**
     * @return if the Drag Image support is available on this platform
     */

    public static boolean isDragImageSupported() {
    Toolkit t = Toolkit.getDefaultToolkit();

    Boolean supported;

    try {
        supported = (Boolean)Toolkit.getDefaultToolkit().getDesktopProperty("DnD.isDragImageSupported");

        return supported.booleanValue();
    } catch (Exception e) {
        return false;
    }
    }

    /**
     * construct a DragSource
     */

    public DragSource() { super(); }

    /**
     * start a Drag operation.
     *
     * @param c            The Component the Drag trigger occurred in
     * @param trigger        The AWTEvent that initiated the operation
     * @param actions        The drag "verbs" appropriate
     * @param dragCursor    The initial cursor or null for defaults
     * @param dragImage        The image to drag or null
     * @param imageOffset    The offset of the image origin from the hotspot
     *                of the cursor at the instant of the trigger
     * @param transferable    The subject data of the operation
     * @param dsl        The DragSourceListener
     *
     * Caller must have AWTPermission startDrag to succeed.
     *
     * @throw java.awt.dnd.InvalidDnDOperationException
     * @throw java.lang.SecurityException
     */

    public void startDrag(Component         c,
                  AWTEvent         trigger,
              int             actions,
              Cursor         dragCursor,
              Image             dragImage,
              Point             imageOffset,
              Transferable         transferable,
              DragSourceListener dsl) throws InvalidDnDOperationException, SecurityException {

    /*
     * FIX THIS FOR BETA4
     */

    // java.security.AccessController.checkPermission(new AWTPermission("startDrag"));

    DragSourceContextPeer dscp = Toolkit.getDefaultToolkit().createDragSourceContextPeer(this, c);
    DragSourceContext     dsc = createDragSourceContext(dscp,
                                c,
                                actions,
                                dragCursor,
                                dragImage,
                                imageOffset,
                                transferable,
                                dsl
                    );

    if (dsc == null) throw new InvalidDnDOperationException();

    dscp.startDrag(dsc, trigger, dsc.getCursor(), actions); // may throw
}

    /**
     * Create the DragSourceContext to handle this Drag.
     *
     * To incorporate a new DragSourceContext subclass, subclass DragSource and
     * override this method.
     *
     * @param dscp         The DragSourceContextPeer for this operation
     * @param c            The Component the drag started in
     * @param actions        The drag "verbs" appropriate
     * @param dragCursor    The initial cursor
     * @param dragImage        The image to drag or null
     * @param imageOffset    The offset of the image origin from the hotspot
     *                of the cursor at the instant of the trigger
     * @param transferable    The subject data of the operation
     * @param dsl        The DragSourceListener
     */

    protected DragSourceContext createDragSourceContext(DragSourceContextPeer dscp, Component c, int actions, Cursor dragCursor, Image dragImage, Point imageOffset, Transferable t, DragSourceListener dsl) {
    return new DragSourceContext(this, dscp, c, actions, dragCursor, dragImage, imageOffset, t, dsl);
    }

    /**
     * @return the FlavorMap for this DragSource
     */

    public FlavorMap getFlavorMap() { return flavorMap; }
}