工作台窗口的Editor区域默认是显示的，而且它支持拖拽操作。在Eclipse里面，把一个文件拖到Editor区域，就会自动打开该文件的Editor。该特性是在IWorkbenchWindowConfigurer 中设置。
在Password Gate中，当拖动Password Gate View中的一个Group 或者 Service到Editor区域，会在Editor显示该项的属性。
要实现此特性，有四部分是必须的。
1 实现必要的Transfer类型，而且定义Editor要支持哪些类型。在Password Gate中，Transfer是LocalSelectionTransfer。Transfer用来进行数据的序列化，它可以支持在同一个程序，或不同程序间拖拽。
2 因为在拖拽传递的过程中Editor Input 要实现序列化，所以要实现IPersistableElement接口。
3 加入一个释放适配器，当一个元素被扔到Editor区域，它可以知道如何进行操作，其实就是打开该元素的Editor。
4 使Password View能够进行拖操作，它要提供供拖的元素。
下面进行代码实现。
在RCP的WorkbenchWindowAdvisor. preWindowOpen中定义要求Editor Area支持的拖入对象的类型，以及打开相应Editor的事件。
ApplicationWorkbenchWindowAdvisor.preWindowOpen()
01 public void preWindowOpen() {
02 ......
03 configurer.addEditorAreaTransfer(LocalSelectionTransfer.getInstance());
04 configurer.configureEditorAreaDropListener(new EditorAreaDropAdapter(
05 configurer.getWindow()));
06 }
Row 03定义了Editor Area支持的Transfer为LocalSelectionTransfer, LocalSelectionTransfer为自己实现的传输介质类。Row 04定义了对拖入Editor Area的对象的处理方法。EditorAreaDropAdapter实现了DropTargetListener接口，用来监听Editor Area中的Drop事件，它会打开拖入Editor Area的对象所对应的Editor，如果同时拖入多个对象，它会打开每个对象对应的Editor.
EditorAreaDropAdapter.java
01 public class EditorAreaDropAdapter extends DropTargetAdapter {
02 private IWorkbenchWindow window;
03
04 public EditorAreaDropAdapter(IWorkbenchWindow window) {
05 this.window = window;
06 }
07
08 public void dragEnter(DropTargetEvent event) {
09 // always indicate a copy
10 event.detail = DND.DROP_COPY;
11 }
12
13 public void dragOperationChanged(DropTargetEvent event) {
14 // always indicate a copy
15 event.detail = DND.DROP_COPY;
16 }
17
18 public void drop(final DropTargetEvent event) {
19 Display d = window.getShell().getDisplay();
20 final IWorkbenchPage page = window.getActivePage();
21 if (page != null) {
22 d.asyncExec(new Runnable() {
23 public void run() {
24 asyncDrop(event, page);
25 }
26 });
27 }
28 }
29
30 private void asyncDrop(DropTargetEvent event, IWorkbenchPage page) {
31 if (LocalSelectionTransfer.getInstance().isSupportedType(
32 event.currentDataType)) {
33 StructuredSelection selection = (StructuredSelection) event.data;
34 for (Iterator iter = selection.iterator(); iter.hasNext();) {
35 Object o = iter.next();
36 if (o instanceof Record) {
37 IEditorInput input = new RecordEditorInput((Record) o);
38 try {
39 page.openEditor(input, RecordEditor.ID);
40 } catch (Exception e) {
41 PwdgatePlugin.log("open ediotr RecordEditor", e);
42 }
43 } else if (o instanceof Group) {
44 IEditorInput input = new GroupEditorInput((Group) o);
45 try {
46 page.openEditor(input, GroupEditor.ID);
47 } catch (PartInitException e) {
48 PwdgatePlugin.log("open ediotr GroupEditor", e);
49 }
50 }
51 }
52 }
53 }
54 }
Row 18，用来处理Drop事件，Row 30的asyncDrop()方法用来打来相应对象的Editor.
现在Editor Area已经可以接收拖入对象了。下一步要使一个View支持拖出对象的功能。下面的例子是在Pass Gate View中的createPartControl()方法中为一个TreeViewer添加拖出功能。
PassGateView.java
01 private void initDragAndDrop() {
02 Transfer[] transfer = new Transfer[] { LocalSelectionTransfer
03 .getInstance() };
04 LocalSelectionDragAdapter adapter = new LocalSelectionDragAdapter(
05 viewer);
06 viewer.addDragSupport(DND.DROP_MOVE | DND.DROP_COPY, transfer, adapter);
07
08 LocalSelectionDropAdapter dropAdapter = new LocalSelectionDropAdapter(
09 viewer);
10 viewer.addDropSupport(DND.DROP_MOVE | DND.DROP_COPY, transfer,
11 dropAdapter);
12 }
Row 06 为TreeViewer添加了监听拖动的事件，当在TreeViewer中有拖动时，LocalSelectionDragAdapter把拖动的对象放入LocalSelectionTransfer中，通过其传到 Editor Area中。
LocalSelectionDragAdapter.java
01 public class LocalSelectionDragAdapter extends DragSourceAdapter {
02
03 ISelectionProvider selectionProvider;
04
05 public LocalSelectionDragAdapter(ISelectionProvider provider) {
06 selectionProvider = provider;
07 }
08
09 public void dragFinished(DragSourceEvent event) {
10 // TODO Auto-generated method stub
11 super.dragFinished(event);
12 System.out
13 .println("DragSourceListener.dragFinished(DragSourceEvent event)");
14 }
15
16 public void dragSetData(DragSourceEvent event) {
17 System.out
18 .println("DragSourceListener.dragSetData(DragSourceEvent event)");
19 DragSource dragSource = (DragSource) event.widget;
20 Control control = dragSource.getControl();
21 if (control != control.getDisplay().getFocusControl()) {
22 event.doit = false;
23 return;
24 }
25
26 IStructuredSelection selection = (IStructuredSelection) selectionProvider
27 .getSelection();
28
29 if (selection.isEmpty()) {
30 event.doit = false;
31 return;
32 }
33 LocalSelectionTransfer.getInstance().setSelection(selection);
34 event.doit = true;
35 }
36
37 public void dragStart(DragSourceEvent event) {
38 System.out
39 .println("DragSourceListener.dragStart(DragSourceEvent event)");
40 }
41 }
Row 33 ，将拖动的对象放入LocalSelectionTransfer中。Row 44 设置拖动有效，设为false的话，拖动无效。下面是LocalSelectionTransfer的实现。很容易理解。
LocalSelectionTransfer.java
001 public class LocalSelectionTransfer extends ByteArrayTransfer {
002
003 private static final String TYPE_NAME = "local-selection-transfer-format" + (new Long(System.currentTimeMillis())).toString(); //$NON-NLS-1$;
004
005 private static final int TYPEID = registerType(TYPE_NAME);
006
007 private static final LocalSelectionTransfer INSTANCE = new LocalSelectionTransfer();
008
009 private ISelection selection;
010
011 private long selectionSetTime;
012
013 /**
014 * Only the singleton instance of this class may be used.
015 */
016 private LocalSelectionTransfer() {
017 }
018
019 /**
020 * Returns the singleton.
021 *
022 * @return LocalSelectionTransfer
023 */
024 public static LocalSelectionTransfer getInstance() {
025 return INSTANCE;
026 }
027
028 /**
029 * Returns the local transfer data.
030 *
031 * @return the local transfer data
032 */
033 public ISelection getSelection() {
034 return selection;
035 }
036
037 /**
038 * Tests whether native drop data matches this transfer type.
039 *
040 * @param result
041 * result of converting the native drop data to Java
042 * @return true if the native drop data does not match this transfer type.
043 * false otherwise.
044 */
045 private boolean isInvalidNativeType(Object result) {
046 return !(result instanceof byte[])
047 || !TYPE_NAME.equals(new String((byte[]) result));
048 }
049
050 /**
051 * Returns the type id used to identify this transfer.
052 *
053 * @return the type id used to identify this transfer.
054 */
055 protected int[] getTypeIds() {
056 return new int[] { TYPEID };
057 }
058
059 /**
060 * Returns the type name used to identify this transfer.
061 *
062 * @return the type name used to identify this transfer.
063 */
064 protected String[] getTypeNames() {
065 return new String[] { TYPE_NAME };
066 }
067
068 /**
069 * Overrides org.eclipse.swt.dnd.ByteArrayTransfer#javaToNative(Object,
070 * TransferData). Only encode the transfer type name since the selection is
071 * read and written in the same process.
072 *
073 * @see org.eclipse.swt.dnd.ByteArrayTransfer#javaToNative(java.lang.Object,
074 * org.eclipse.swt.dnd.TransferData)
075 */
076 public void javaToNative(Object object, TransferData transferData) {
077 byte[] check = TYPE_NAME.getBytes();
078 super.javaToNative(check, transferData);
079 }
080
081 /**
082 * Overrides
083 * org.eclipse.swt.dnd.ByteArrayTransfer#nativeToJava(TransferData). Test if
084 * the native drop data matches this transfer type.
085 *
086 * @see org.eclipse.swt.dnd.ByteArrayTransfer#nativeToJava(TransferData)
087 */
088 public Object nativeToJava(TransferData transferData) {
089 Object result = super.nativeToJava(transferData);
090 if (isInvalidNativeType(result)) {
091 PwdgatePlugin.log("invalid nattive type", new Exception(
092 "invalid nattive type"));
093 }
094 return selection;
095 }
096
097 /**
098 * Sets the transfer data for local use.
099 *
100 * @param s
101 * the transfer data
102 */
103 public void setSelection(ISelection s) {
104 selection = s;
105 }
106
107 /**
108 * Returns the time when the selection operation this transfer is associated
109 * with was started.
110 *
111 * @return the time when the selection operation has started
112 *
113 * @see org.eclipse.swt.events.TypedEvent#time
114 */
115 public long getSelectionSetTime() {
116 return selectionSetTime;
117 }
118
119 /**
120 * Sets the time when the selection operation this transfer is associated
121 * with was started. If assigning this from an SWT event, be sure to use
122 * <code>setSelectionTime(event.time & 0xFFFF)</code>
123 *
124 * @param time
125 * the time when the selection operation was started
126 *
127 * @see org.eclipse.swt.events.TypedEvent#time
128 */
129 public void setSelectionSetTime(long time) {
130 selectionSetTime = time;
131 }
132 }
其实不光是拖到Area Editor，以上例子稍加改造，也可以实现拖到别的控件中，任何Control都可以添加托拽功能，例如可以从一个表格拖到另一个表格中，或拖到一个面板中。托拽功能让软件的可用性又提高了一个档次。
