dragsource.java

JAVA基本类源代码,大家可以学习学习!

    /**
     * Adds the specified <code>DragSourceMotionListener</code> to this
     * <code>DragSource</code> to receive drag motion 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 dsml the <code>DragSourceMotionListener</code> to add
     *
     * @see      #removeDragSourceMotionListener
     * @see      #getDragSourceMotionListeners
     * @since 1.4
     */
    public void addDragSourceMotionListener(DragSourceMotionListener dsml) {
	if (dsml != null) {
            synchronized (this) {
                motionListener = DnDEventMulticaster.add(motionListener, dsml);
            }
        }
    }

    /**
     * Removes the specified <code>DragSourceMotionListener</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 dsml the <code>DragSourceMotionListener</code> to remove
     *
     * @see      #addDragSourceMotionListener
     * @see      #getDragSourceMotionListeners
     * @since 1.4
     */
    public void removeDragSourceMotionListener(DragSourceMotionListener dsml) {
        if (dsml != null) {
            synchronized (this) {
                motionListener = DnDEventMulticaster.remove(motionListener, dsml);
            }
        }
    }

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

    /**
     * Gets all the objects currently registered as
     * <code><em>Foo</em>Listener</code>s upon this <code>DragSource</code>.
     * <code><em>Foo</em>Listener</code>s are registered using the
     * <code>add<em>Foo</em>Listener</code> method.
     *
     * @param listenerType the type of listeners requested; this parameter
     *          should specify an interface that descends from
     *          <code>java.util.EventListener</code>
     * @return an array of all objects registered as
     *          <code><em>Foo</em>Listener</code>s on this
     *          <code>DragSource</code>, or an empty array if no such listeners
     *          have been added 
     * @exception <code>ClassCastException</code> if <code>listenerType</code>
     *          doesn't specify a class or interface that implements
     *          <code>java.util.EventListener</code>
     *
     * @see #getDragSourceListeners
     * @see #getDragSourceMotionListeners
     * @since 1.4
     */
    public EventListener[] getListeners(Class listenerType) { 
        EventListener l = null; 
        if (listenerType == DragSourceListener.class) { 
            l = listener;
        } else if (listenerType == DragSourceMotionListener.class) {
            l = motionListener;
        }
        return DnDEventMulticaster.getListeners(l, listenerType);
    }

    /**
     * This method calls <code>dragEnter</code> on the
     * <code>DragSourceListener</code>s registered with this
     * <code>DragSource</code>, and passes them the specified
     * <code>DragSourceDragEvent</code>.
     *
     * @param dsde the <code>DragSourceDragEvent</code>
     */
    void processDragEnter(DragSourceDragEvent dsde) {
        DragSourceListener dsl = listener;
        if (dsl != null) {
            dsl.dragEnter(dsde);
        }
    }

    /**
     * This method calls <code>dragOver</code> on the
     * <code>DragSourceListener</code>s registered with this
     * <code>DragSource</code>, and passes them the specified
     * <code>DragSourceDragEvent</code>.
     *
     * @param dsde the <code>DragSourceDragEvent</code>
     */
    void processDragOver(DragSourceDragEvent dsde) {
        DragSourceListener dsl = listener;
        if (dsl != null) {
            dsl.dragOver(dsde);
        }
    }

    /**
     * This method calls <code>dropActionChanged</code> on the
     * <code>DragSourceListener</code>s registered with this
     * <code>DragSource</code>, and passes them the specified
     * <code>DragSourceDragEvent</code>.
     *
     * @param dsde the <code>DragSourceDragEvent</code>
     */
    void processDropActionChanged(DragSourceDragEvent dsde) {
        DragSourceListener dsl = listener;
        if (dsl != null) {
            dsl.dropActionChanged(dsde);
        }
    }

    /**
     * This method calls <code>dragExit</code> on the
     * <code>DragSourceListener</code>s registered with this
     * <code>DragSource</code>, and passes them the specified
     * <code>DragSourceEvent</code>.
     *
     * @param dse the <code>DragSourceEvent</code>
     */
    void processDragExit(DragSourceEvent dse) {
        DragSourceListener dsl = listener;
        if (dsl != null) {
            dsl.dragExit(dse);
        }
    }

    /**
     * This method calls <code>dragDropEnd</code> on the
     * <code>DragSourceListener</code>s registered with this
     * <code>DragSource</code>, and passes them the specified
     * <code>DragSourceDropEvent</code>.
     *
     * @param dsde the <code>DragSourceEvent</code>
     */
    void processDragDropEnd(DragSourceDropEvent dsde) {
        DragSourceListener dsl = listener;
        if (dsl != null) {
            dsl.dragDropEnd(dsde);
        }
    }

    /**
     * This method calls <code>dragMouseMoved</code> on the
     * <code>DragSourceMotionListener</code>s registered with this
     * <code>DragSource</code>, and passes them the specified
     * <code>DragSourceDragEvent</code>.
     *
     * @param dsde the <code>DragSourceEvent</code>
     */
    void processDragMouseMoved(DragSourceDragEvent dsde) {
        DragSourceMotionListener dsml = motionListener;
        if (dsml != null) {
            dsml.dragMouseMoved(dsde);
        }
    }

    /**
     * Serializes this <code>DragSource</code>. This method first performs
     * default serialization. Next, it writes out this object's
     * <code>FlavorMap</code> if and only if it can be serialized. If not,
     * <code>null</code> is written instead. Next, it writes out
     * <code>Serializable</code> listeners registered with this
     * object. Listeners are written in a <code>null</code>-terminated sequence
     * of 0 or more pairs. The pair consists of a <code>String</code> and an
     * <code>Object</code>; the <code>String</code> indicates the type of the
     * <code>Object</code> and is one of the following:
     * <ul>
     * <li><code>dragSourceListenerK</code> indicating a
     *     <code>DragSourceListener</code> object;
     * <li><code>dragSourceMotionListenerK</code> indicating a
     *     <code>DragSourceMotionListener</code> object.
     * </ul>
     *
     * @serialData Either a <code>FlavorMap</code> instance, or
     *      <code>null</code>, followed by a <code>null</code>-terminated
     *      sequence of 0 or more pairs; the pair consists of a
     *      <code>String</code> and an <code>Object</code>; the
     *      <code>String</code> indicates the type of the <code>Object</code>
     *      and is one of the following:
     *      <ul>
     *      <li><code>dragSourceListenerK</code> indicating a
     *          <code>DragSourceListener</code> object;
     *      <li><code>dragSourceMotionListenerK</code> indicating a
     *          <code>DragSourceMotionListener</code> object.
     *      </ul>.
     * @since 1.4
     */
    private void writeObject(ObjectOutputStream s) throws IOException {
        s.defaultWriteObject();

        s.writeObject(SerializationTester.test(flavorMap) ? flavorMap : null);

        DnDEventMulticaster.save(s, dragSourceListenerK, listener);
        DnDEventMulticaster.save(s, dragSourceMotionListenerK, motionListener);
        s.writeObject(null);
    }

    /**
     * Deserializes this <code>DragSource</code>. This method first performs
     * default deserialization. Next, this object's <code>FlavorMap</code> is 
     * deserialized by using the next object in the stream.
     * If the resulting <code>FlavorMap</code> is <code>null</code>, this
     * object's <code>FlavorMap</code> is set to the default FlavorMap for
     * this thread's <code>ClassLoader</code>.
     * Next, this object's listeners are deserialized by reading a
     * <code>null</code>-terminated sequence of 0 or more key/value pairs
     * from the stream: 
     * <ul>
     * <li>If a key object is a <code>String</code> equal to
     * <code>dragSourceListenerK</code>, a <code>DragSourceListener</code> is 
     * deserialized using the corresponding value object and added to this
     * <code>DragSource</code>. 
     * <li>If a key object is a <code>String</code> equal to
     * <code>dragSourceMotionListenerK</code>, a
     * <code>DragSourceMotionListener</code> is deserialized using the
     * corresponding value object and added to this <code>DragSource</code>.
     * <li>Otherwise, the key/value pair is skipped.
     * </ul>
     *
     * @see java.awt.datatransfer.SystemFlavorMap#getDefaultFlavorMap
     * @since 1.4
     */
    private void readObject(ObjectInputStream s) 
      throws ClassNotFoundException, IOException {
        s.defaultReadObject();

        // 'flavorMap' was written explicitly
        flavorMap = (FlavorMap)s.readObject();

        // Implementation assumes 'flavorMap' is never null.
        if (flavorMap == null) {
            flavorMap = SystemFlavorMap.getDefaultFlavorMap();
        }

        Object keyOrNull;
        while (null != (keyOrNull = s.readObject())) {
            String key = ((String)keyOrNull).intern();

            if (dragSourceListenerK == key) {
                addDragSourceListener((DragSourceListener)(s.readObject()));
            } else if (dragSourceMotionListenerK == key) {
                addDragSourceMotionListener(
                    (DragSourceMotionListener)(s.readObject()));
            } else { 
                // skip value for unrecognized key
                s.readObject();
            }
        }
    }

    /*
     * fields
     */

    private transient FlavorMap flavorMap = SystemFlavorMap.getDefaultFlavorMap();

    private transient DragSourceListener listener;

    private transient DragSourceMotionListener motionListener;
}