dragsource.java

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            DragSourceContextPeer dscp = Toolkit.getDefaultToolkit().createDragSourceContextPeer(trigger);

            DragSourceContext     dsc = createDragSourceContext(dscp,
                                                                trigger,
                                                                dragCursor,
                                                                dragImage,
                                                                imageOffset,
                                                                transferable,
                                                                dsl
                                                                );
            
            if (dsc == null) {
                throw new InvalidDnDOperationException();
            }
							    
            dscp.startDrag(dsc, dsc.getCursor(), dragImage, imageOffset); // may throw
        } catch (RuntimeException e) {
            SunDragSourceContextPeer.setDragDropInProgress(false);
            throw e;
        }
    }

    /**
     * Start a drag, given the <code>DragGestureEvent</code> 
     * that initiated the drag, the initial 
     * <code>Cursor</code> to use,
     * the <code>Transferable</code> subject data 
     * of the drag, the <code>DragSourceListener</code>, 
     * and the <code>FlavorMap</code>. 
     * <P>
     * @param trigger	     the <code>DragGestureEvent</code> that 
     * initiated the drag
     * @param dragCursor     the initial <code>Cursor</code> or 
     * <code>null</code> for defaults
     * @param transferable   the subject data of the drag
     * @param dsl	     the <code>DragSourceListener</code>
     * @param flavorMap	     the <code>FlavorMap to use or <code>null</code>
     * <P>
     * @throws <code>java.awt.dnd.InvalidDnDOperationException</code> 
     *    if the Drag and Drop
     *    system is unable to initiate a drag operation, or if the user
     *    attempts to start a drag while an existing drag operation 
     *    is still executing
     */

    public void startDrag(DragGestureEvent   trigger,
			  Cursor	     dragCursor,
			  Transferable	     transferable,
			  DragSourceListener dsl,
			  FlavorMap	     flavorMap) throws InvalidDnDOperationException {
	startDrag(trigger, dragCursor, null, null, transferable, dsl, flavorMap);
    }

    /**
     * Start a drag, given the <code>DragGestureEvent</code> 
     * that initiated the drag, the initial <code>Cursor</code> 
     * to use,
     * the <code>Image</code> to drag, 
     * the offset of the <code>Image</code> origin 
     * from the hotspot of the <code>Cursor</code>
     * at the instant of the trigger,
     * the subject data of the drag, and 
     * the <code>DragSourceListener</code>. 
     * <P>
     * @param trigger		the <code>DragGestureEvent</code> that initiated the drag
     * @param dragCursor	the initial <code>Cursor</code> or <code>null</code> for defaults
     * @param dragImage		the <code>Image</code> to drag or <code>null</code>
     * @param dragOffset	the offset of the <code>Image</code> origin from the hotspot
     *				of the <code>Cursor</code> at the instant of the trigger
     * @param transferable	the subject data of the drag
     * @param dsl		the <code>DragSourceListener</code>
     * <P>
     * @throws <code>java.awt.dnd.InvalidDnDOperationException</code> 
     *    if the Drag and Drop
     *    system is unable to initiate a drag operation, or if the user
     *    attempts to start a drag while an existing drag operation  
     *    is still executing
     */

    public void startDrag(DragGestureEvent   trigger,
			  Cursor	     dragCursor,
			  Image		     dragImage,
			  Point		     dragOffset,
			  Transferable	     transferable,
			  DragSourceListener dsl) throws InvalidDnDOperationException {
	startDrag(trigger, dragCursor, dragImage, dragOffset, transferable, dsl, null);
    }

    /**
     * Start a drag, given the <code>DragGestureEvent</code> 
     * that initiated the drag, the initial 
     * <code>Cursor</code> to 
     * use, 
     * the <code>Transferable</code> subject data 
     * of the drag, and the <code>DragSourceListener</code>. 
     * <P>
     * @param trigger		the <code>DragGestureEvent</code> that initiated the drag
     * @param dragCursor	the initial <code>Cursor</code> or <code>null</code> for defaults
     * @param transferable	the subject data of the drag
     * @param dsl		the <code>DragSourceListener</code>
     * <P>
     * @throws <code>java.awt.dnd.InvalidDnDOperationException</code> 
     *    if the Drag and Drop
     *    system is unable to initiate a drag operation, or if the user
     *    attempts to start a drag while an existing drag operation 
     *    is still executing
     */

    public void startDrag(DragGestureEvent   trigger,
			  Cursor	     dragCursor,
			  Transferable	     transferable,
			  DragSourceListener dsl) throws InvalidDnDOperationException {
	startDrag(trigger, dragCursor, null, null, transferable, dsl, null);
    }

    /**
     * Creates the <code>DragSourceContext</code> to handle this drag.
     * <p> 
     * To incorporate a new <code>DragSourceContext</code> 
     * subclass, subclass <code>DragSource</code> and
     * override this method.
     * <p>
     * If <code>dragImage</code> is <code>null</code>, no image is used 
     * to represent the drag over feedback for this drag operation, but 
     * <code>NullPointerException</code> is not thrown.
     * <p>
     * If <code>dsl</code> is <code>null</code>, no drag source listener 
     * is registered with the created <code>DragSourceContext</code>,  
     * but <code>NullPointerException</code> is not thrown.
     * <p>
     * If <code>dragCursor</code> is <code>null</code>, the default drag 
     * cursors are used for this drag operation.  
     * <code>NullPointerException</code> is not thrown.
     *
     * @param dscp          The <code>DragSourceContextPeer</code> for this drag
     * @param dgl	    The <code>DragGestureEvent</code> that triggered the 
     *                      drag
     * @param dragCursor    The initial <code>Cursor</code> to display
     * @param dragImage	    The <code>Image</code> to drag or <code>null</code>
     * @param imageOffset   The offset of the <code>Image</code> origin from the 
     *                      hotspot of the cursor at the instant of the trigger
     * @param t             The subject data of the drag
     * @param dsl	    The <code>DragSourceListener</code>
     * 
     * @return the <code>DragSourceContext</code>
     * 
     * @throws NullPointerException if <code>dscp</code> is <code>null</code>
     * @throws NullPointerException if <code>dgl</code> is <code>null</code>
     * @throws NullPointerException if <code>dragImage</code> is not 
     *    <code>null</code> and <code>imageOffset</code> is <code>null</code>
     * @throws NullPointerException if <code>t</code> is <code>null</code>
     * @throws IllegalArgumentException if the <code>Component</code> 
     *         associated with the trigger event is <code>null</code>.
     * @throws IllegalArgumentException if the <code>DragSource</code> for the 
     *         trigger event is <code>null</code>.
     * @throws IllegalArgumentException if the drag action for the
     *         trigger event is <code>DnDConstants.ACTION_NONE</code>.
     * @throws IllegalArgumentException if the source actions for the
     *         <code>DragGestureRecognizer</code> associated with the trigger
     *         event are equal to <code>DnDConstants.ACTION_NONE</code>. 
     */

    protected DragSourceContext createDragSourceContext(DragSourceContextPeer dscp, DragGestureEvent dgl, Cursor dragCursor, Image dragImage, Point imageOffset, Transferable t, DragSourceListener dsl) {
	return new DragSourceContext(dscp, dgl, dragCursor, dragImage, imageOffset, t, dsl);
    }

    /**
     * This method returns the 
     * <code>FlavorMap</code> for this <code>DragSource</code>.
     * <P>
     * @return the <code>FlavorMap</code> for this <code>DragSource</code>
     */

    public FlavorMap getFlavorMap() { return flavorMap; }

    /**
     * Creates a new <code>DragGestureRecognizer</code> 
     * that implements the specified
     * abstract subclass of 
     * <code>DragGestureRecognizer</code>, and 
     * sets the specified <code>Component</code> 
     * and <code>DragGestureListener</code> on 
     * the newly created object.
     * <P>
     * @param recognizerAbstractClass the requested abstract type
     * @param actions		      the permitted source drag actions
     * @param c			      the <code>Component</code> target 
     * @param dgl	 the <code>DragGestureListener</code> to notify
     * <P>
     * @return the new <code>DragGestureRecognizer</code> or <code>null</code>
     *    if the <code>Toolkit.createDragGestureRecognizer</code> method
     *    has no implementation available for 
     *    the requested <code>DragGestureRecognizer</code>
     *    subclass and returns <code>null</code>
     */

    public DragGestureRecognizer createDragGestureRecognizer(Class recognizerAbstractClass, Component c, int actions, DragGestureListener dgl) {
	return Toolkit.getDefaultToolkit().createDragGestureRecognizer(recognizerAbstractClass, this, c, actions, dgl);
    }

	
    /**
     * Creates a new <code>DragGestureRecognizer</code> 
     * that implements the default
     * abstract subclass of <code>DragGestureRecognizer</code>
     * for this <code>DragSource</code>,
     * and sets the specified <code>Component</code> 
     * and <code>DragGestureListener</code> on the
     * newly created object. 
     *
     * For this <code>DragSource</code> 
     * the default is <code>MouseDragGestureRecognizer</code>.
     * <P>
     * @param c	      the <code>Component</code> target for the recognizer
     * @param actions the permitted source actions
     * @param dgl     the <code>DragGestureListener</code> to notify
     * <P>
     * @return the new <code>DragGestureRecognizer</code> or <code>null</code>
     *    if the <code>Toolkit.createDragGestureRecognizer</code> method
     *    has no implementation available for 
     *    the requested <code>DragGestureRecognizer</code>
     *    subclass and returns <code>null</code>
     */

    public DragGestureRecognizer createDefaultDragGestureRecognizer(Component c, int actions, DragGestureListener dgl) {
	return Toolkit.getDefaultToolkit().createDragGestureRecognizer(MouseDragGestureRecognizer.class, this, c, actions, dgl);
    }

    /**
     * Adds the specified <code>DragSourceListener</code> to this
     * <code>DragSource</code> to receive drag source events during drag
     * operations intiated with this <code>DragSource</code>.
     * If a <code>null</code> listener is specified, no action is taken and no
     * exception is thrown.
     *
     * @param dsl the <code>DragSourceListener</code> to add
     *
     * @see      #removeDragSourceListener
     * @see      #getDragSourceListeners
     * @since 1.4
     */
    public void addDragSourceListener(DragSourceListener dsl) {
	if (dsl != null) {
            synchronized (this) {
                listener = DnDEventMulticaster.add(listener, dsl);
            }
        }
    }

    /**
     * Removes the specified <code>DragSourceListener</code> from this
     * <code>DragSource</code>. 
     * If a <code>null</code> listener is specified, no action is taken and no
     * exception is thrown.
     * If the listener specified by the argument was not previously added to
     * this <code>DragSource</code>, no action is taken and no exception
     * is thrown.
     * 
     * @param dsl the <code>DragSourceListener</code> to remove
     *
     * @see      #addDragSourceListener
     * @see      #getDragSourceListeners
     * @since 1.4
     */
    public void removeDragSourceListener(DragSourceListener dsl) {
        if (dsl != null) {
            synchronized (this) {
                listener = DnDEventMulticaster.remove(listener, dsl);
            }
        }
    }

    /**
     * Gets all the <code>DragSourceListener</code>s
     * registered with this <code>DragSource</code>.
     *
     * @return all of this <code>DragSource</code>'s
     *         <code>DragSourceListener</code>s or an empty array if no
     *         such listeners are currently registered
     *
     * @see      #addDragSourceListener
     * @see      #removeDragSourceListener
     * @since    1.4
     */
    public DragSourceListener[] getDragSourceListeners() {
        return (DragSourceListener[])getListeners(DragSourceListener.class);
    }