基于选择的Eclipse RCP处理程序支持

Question

I'm a bit stuck, because the resources are many and they don't clarfiy this issue for me.

Suppose I have a , a , a , and the result of these presented on the UI as a .

Now, suppose I have several view extending the same base (eg BaseView ). All of these views contain ColumnViewer s (eg TableViewer , TreeViewer ) which act as .

• How does the enableWhen and activeWhen configurations know about the selection in those viewers? I can't imagine how the selection + instanceOf parameters work for ISelection (s).
• How is the selected object passed to the property tester? What instance do the test method receive (as the receiver )?
• I noticed with a breakpoint that there are many passes through the setEnabled() method of the handler. Is that normal behaviour? Would it be okay to override the setEnabled ?

---

Code seems a little bit irrelevant to me here. But anyway, these snippets cover the questions:

// --------------------- 1 -----------------------

  <handler
        class="com.example.ggrec.handlers.SampleHandler"
        commandId="com.example.ggrec.commands.sampleCommand">
     <enabledWhen>
        <with
              variable="selection">
           <instanceof
                 value="org.eclipse.jface.viewers.ISelection">
           </instanceof>
        </with>
     </enabledWhen>
  </handler>

// --------------------- 2 -----------------------

  <propertyTester
        class="com.example.ggrec.propertyTesters.SamplePropertyTester"
        id="com.example.ggrec.samplePropertyTester"
        namespace="com.example.ggrec.propertyTesters"
        properties="simpleTest"
        type="java.lang.Object">
  </propertyTester>

// --------------------- 3 -----------------------

/**
 * 
 * @author ggrec
 *
 */
public class SamplePropertyTester extends PropertyTester
{
    @Override
    public boolean test(final Object receiver, final String property, final Object[] args, final Object expectedValue)
    {
        if (receiver instanceof ISelection) // What instance is this?
            System.out.println("RAINBOWS");

        return true;
    }
}

// --------------------- 4 -----------------------

/**
 * 
 * @author ggrec
 *
 */
public class SampleHandler extends AbstractHandler
{
    @Override
    public Object execute(final ExecutionEvent event) throws ExecutionException 
    {
        final IWorkbenchWindow window = HandlerUtil.getActiveWorkbenchWindowChecked(event);
        MessageDialog.openInformation(window.getShell(), "", "meh");

        return null;
    }

    @Override
    public void setEnabled(final Object evaluationContext)
    {
        super.setEnabled(evaluationContext); // Goes like crazy through here.
    }
}

Answer 1

Each ViewPart (and editor part) has a separate selection maintained by the selection service and set by your selection providers. The enabledWhen and visibleWhen use the selection for the currently active part obtained from the selection service for the part.

The property test calls are usually inside a <with> block in the enablement expression which establishes the object that is being tested. Something like:

<with
    variable="org.eclipse.ui.selection">
   <iterate
         operator="or">
      <adapt
            type="music.resources.data.IMusicFile">
            <or>
                <test property="music.isMusicOrPlaylist"/>
                <test property="music.isVideo"/>
            </or>
       </adapt>
    </iterate>
</with>

which is working with the current selection, requiring the selection to adapt to a particular type, and testing either of two properties.