在開發Eclipse 外掛時, 想在工具欄中增加一個按鈕圖示是非常容易, 但是想在圖示上增加子選單就會比較麻煩, 例如想實現如下效果: 

具體步驟如下:

1. 首先在擴充套件點org.eclipse.ui.commands中增加三個指令
   
   
   1. <extension
   2.     point="org.eclipse.ui.commands">
   3.     <command
   4.         name="Reference Command"
   5.         id="top.itart.plugin.smartboot.referenceCommand">
   6.     </command
      >
   7.     <command
   8.         name="Sub1 Command"
   9.         id="top.itart.plugin.smartboot.sub1Command">
   10.     </command>
   11.     <command
   12.         name="Sub2 Command"
   13.         id="top.itart.plugin.smartboot.sub2Command">
   14.     </command>
   15. </extension>
   
   
   
2. 其次在擴充套件點org.eclipse.ui.menus 增加兩個menuContribution
   
   
   1. <
      menuContribution
   2.     locationURI="toolbar:org.eclipse.ui.main.toolbar?after=additions">
   3.     <toolbar
   4.        id="top.itart.plugin.smartboot.toolbars">
   5.         <command
   6.               commandId="top.itart.plugin.smartboot.referenceCommand"
   7.               icon="icons/sample.gif"
   8.               tooltip
      ="Pull down"style="pulldown">
   9.         </command>
   10.     </toolbar>
   11. </menuContribution>
   
   這個是定義顯示在toolbar上的選單. Command 中的commandId 為第一個指令的ID, 型別 type 為pulldown, 並且放在toolbar標籤中
   
   
   1. <menuContribution
   2.     locationURI="menu:top.itart.plugin.smartboot.referenceCommand">
   3.     <command
   4.               commandId="top.itart.plugin.smartboot.sub1Command"
   5.               icon="icons/sample.gif"
   6.               label = "Sub 1"
   7.               tooltip="Sub 1">
   8.     </command>
   9.     <command
   10.         commandId="top.itart.plugin.smartboot.sub2Command"
   11.         icon="icons/sample.gif"
   12.         tooltip="Sub2"
   13.         label = "Sub 2">
   14.     </command>
   15. </menuContribution>
   
   這個menuContribution是定義下拉的子選單. 注意locationURI的值是menu: <Toolbar上的選單ID>
   
   

• 最終的plugin.xml如下

1. <?xmlversion="1.0"encoding="UTF-8"?>
2. <?eclipseversion="3.4"?>
3. <plugin>
4.     <extension
5.         point="org.eclipse.ui.commands">
6.         <command
7.             name="Reference Command"
8.             id="top.itart.plugin.smartboot.referenceCommand">
9.         </command>
10.         <command
11.             name="Sub1 Command"
12.             id="top.itart.plugin.smartboot.sub1Command">
13.         </command>
14.         <command
15.             name="Sub2 Command"
16.             id="top.itart.plugin.smartboot.sub2Command">
17.         </command>
18.     </extension>
19.    <extension
20.          point="org.eclipse.ui.menus">
21.         <menuContribution
22.             locationURI="toolbar:org.eclipse.ui.main.toolbar?after=additions">
23.             <toolbar
24.                id="top.itart.plugin.smartboot.toolbars">
25.                 <command
26.                       commandId="top.itart.plugin.smartboot.referenceCommand"
27.                       icon="icons/sample.gif"
28.                       tooltip="Pull down"style="pulldown">
29.                 </command>
30.             </toolbar>
31.         </menuContribution>
32.         <menuContribution
33.             locationURI="menu:top.itart.plugin.smartboot.referenceCommand">
34.             <command
35.                       commandId="top.itart.plugin.smartboot.sub1Command"
36.                       icon="icons/sample.gif"
37.                       label = "Sub 1"
38.                       tooltip="Sub 1">
39.             </command>
40.             <command
41.                 commandId="top.itart.plugin.smartboot.sub2Command"
42.                 icon="icons/sample.gif"
43.                 tooltip="Sub2"
44.                 label = "Sub 2">
45.             </command>
46.         </menuContribution>
47.     </extension>
48. </plugin>