Eclipse plugin 加载的类的类型不正确：应为（org.eclipse.ui.menus.WorkbenchWindowControlContribution）Get（de.blub.menu.ToolbarContributionItem）

这是我在plugin.xml中的menucontribution：

<menuContribution
        locationURI="toolbar:org.eclipse.ui.main.toolbar?after=additions">
    <dynamic
           class="de.blub.menu.ToolbarContributionItem"
           id="some.id">
         <visibleWhen checkEnabled="false">
            <!-- some conditions -->
         </visibleWhen>
    </dynamic>  
</menuContribution>

但是我得到了错误信息

!MESSAGE Loaded class is of incorrect type: expected(org.eclipse.ui.menus.WorkbenchWindowControlContribution) got (de.blub.menu.ToolbarContributionItem)
!STACK 0
java.lang.IllegalArgumentException: Loaded class is of incorrect type: expected(org.eclipse.ui.menus.WorkbenchWindowControlContribution) got (de.blub.menu.ToolbarContributionItem)
at org.eclipse.ui.internal.util.Util.safeLoadExecutableExtension(Util.java:713)

---

那么这里的问题是什么呢？

文档是错误的，请参阅Eclipse bug

该类必须扩展

org.eclipse.ui.menus.WorkbenchWindowControlControlContribution

!MESSAGE Loaded class is of incorrect type: expected(org.eclipse.ui.menus.WorkbenchWindowControlContribution) got (de.blub.menu.ToolbarContributionItem)
!STACK 0
java.lang.IllegalArgumentException: Loaded class is of incorrect type: expected(org.eclipse.ui.menus.WorkbenchWindowControlContribution) got (de.blub.menu.ToolbarContributionItem)
at org.eclipse.ui.internal.util.Util.safeLoadExecutableExtension(Util.java:713)