Eclipse RCP TreeViewer单/多选右键菜单扩展定义问题

Let's get your right-click menus set up correctly for single and multi-selection scenarios. Here's what you need to do:

1. Detecting Multi-Selection #

To identify when multiple items are selected, you’ll use the <count> element in your expression definition to check that the number of selected items is greater than 1. You’ll also need to ensure every selected item matches one of your ExampleNGroup types (just like the single-selection case), so we’ll combine these two conditions with an <and> operator.

2. Instanceof Values for Multi-Selection #

The <instanceof> values stay exactly the same as your single-selection setup! Since you want the multi-select menu to appear only when all selected items are one of your Example1Group, Example2Group, etc., you’ll reuse the same <or> block of <instanceof> checks for each type.

Full Multi-Selection Expression Definition #

Here’s the complete code for your multi-select expression:

<definition id="com.sample.rightclickmenu.multiselect.id.expression">
  <with variable="org.eclipse.ui.selection">
    <!-- Combine two conditions: count > 1 AND all items are valid types -->
    <and>
      <!-- Check for 2+ selected items -->
      <count value="1" operator="gt"/>
      <!-- Verify every selected item is an ExampleNGroup type -->
      <iterate ifEmpty="false" operator="and">
        <or>
          <instanceof value="com.sample.Example1Group"/>
          <instanceof value="com.sample.Example2Group"/>
          <!-- Add all your ExampleNGroup types here -->
        </or>
      </iterate>
    </and>
  </with>
</definition>

3. Fixing the Single-Selection Expression #

Don’t forget to update your existing single-selection expression to only show when exactly one item is selected—otherwise, it might still appear during multi-selection (since each item individually matches the type check). Add a <count> check to it:

<definition id="com.sample.rightclickmenu.singleselect.id.expression">
  <with variable="org.eclipse.ui.selection">
    <and>
      <!-- Show only when exactly 1 item is selected -->
      <count value="1" operator="eq"/>
      <iterate ifEmpty="false" operator="and">
        <or>
          <instanceof value="com.sample.Example1Group"/>
          <instanceof value="com.sample.Example2Group"/>
          <!-- Keep your existing ExampleNGroup entries here -->
        </or>
      </iterate>
    </and>
  </with>
</definition>

4. Binding to Menu Items #

Finally, link these expressions to your menu items using <visibleWhen>:

For the single-select menu item:

<menuContribution locationURI="popup:your.tree.viewer.id">
  <command
      commandId="com.sample.singleselect.command.id"
      label="Single-Select Action">
    <visibleWhen>
      <reference definitionId="com.samplestring.seJL             tab                   // condition boolean　 construct费getclope, no—just reference the single-select expression ID">
      <reference definitionId="com.sample.rightclickmenu.singleselect.id.expression"/>
    </visibleWhen>
  </command>
</menuContribution>

For the multi-select menu item:

<menuContribution locationURI="popup:your.tree.viewer.id">
  <command
      commandId="com.sample.multiselect.command.id"
      label="Multi-Select Action">
    <visibleWhen>
      <reference definitionId="com.sample.rightclickmenu.multiselect.id.expression"/>
    </visibleWhen>
  </command>
</menuContribution>

That’s it! Now your single-select menu will only show when one valid item is selected, and the multi-select menu will appear when two or more valid items are selected.

内容的提问来源于stack exchange，提问作者user2761431