Where is the connection between toolbar description and the code in Eclipse RCP?

Question

I have added the button in the following way:

<extension
         point="org.eclipse.ui.menus">
      <menuContribution
            locationURI="menu:org.eclipse.ui.main.menu">
         <menu
               label="File">
            <command
                  commandId="org.eclipse.ui.file.exit"
                  label="Exit">
            </command>
         </menu>
      </menuContribution>
      <menuContribution
            allPopups="false"
            locationURI="toolbar:MYVIEWID">
         <command
               commandId="MYCOMMANDID"
               icon="icons/1389818330_Run.png"
               label="Run a bot"
               style="push">
         </command>
      </menuContribution>
   </extension>

In result, toolbar button appears on the view, but it is dimmed and does nothing.

Where to set the code which will execute on this button press?

Answer 1

You use the org.eclipse.ui.handlers extension point to define a handler for the command id.

<extension
     point="org.eclipse.ui.handlers">
  <handler
        class="org.eclipse.ui.examples.contributions.handlers.GlobalMenuHandler"
        commandId="org.eclipse.ui.examples.contributions.commands.globalCommand">
  </handler>
</extension>

You must also use the org.eclipse.ui.commands extension point to define the command id in the first place. You can specify a default handler in the command id definition:

<extension
     point="org.eclipse.ui.handlers">
  <command
        categoryId="org.eclipse.ui.examples.contributions.commands.category"
        defaultHandler="org.eclipse.ui.examples.contributions.handlers.GlobalMenuHandler"
        id="org.eclipse.ui.examples.contributions.commands.globalCommand"
        name="%contributions.commands.globalCommand.name">
  </command>
</extension>

(above examples are from the Eclipse help).

There is also this tutorial on commands.