Change Eclipse toolbar icon dynamically

I've got a toolbar item with its own icon, defined in 开发者_如何转开发the plugin.xml file like:

<action
class="MyActionClass"
id="MyActionID"
label="MyActionLabel"
menubarPath="MyActionMenuBarPath"
toolbarPath="MyActionToolBarPath"
icon="icon/myicon.png" <---- this one
     ...
</action>

How do I change this dynamically when needed? I mean changing it from code

Use org.eclipse.ui.menus extension point instead and add menuContribution with dynamic. The class of dynamic should subclass ControlContribution and implement createControl method to create a button.

You should implements IElementUpdater in your Handler class.
Please refer to : https://stackoverflow.com/a/23742598/2893073

1. Handler class

   import java.util.Map;    
   import org.eclipse.core.commands.AbstractHandler;
   import org.eclipse.core.commands.ExecutionEvent;
   import org.eclipse.core.commands.ExecutionException;
   import org.eclipse.jface.resource.ImageDescriptor;
   import org.eclipse.ui.commands.IElementUpdater;
   import org.eclipse.ui.menus.UIElement;    
   import com.packpub.e4.menu.Activator;     
   public class SampleHandler2 extends 
                AbstractHandler implements IElementUpdater{       
       private static ImageDescriptor image_enable = 
           Activator.getImageDescriptor("icons/btn_adapt_enable.png");
       private static ImageDescriptor image_disable = 
           Activator.getImageDescriptor("icons/btn_adapt_disable.png");        
       /**
        * The constructor.
        */
       public SampleHandler2() {
   
       }    
       /**
        * the command has been executed, so extract extract the needed information
        * from the application context.
        */
       public Object execute(ExecutionEvent event) throws ExecutionException {
           //...
           return null;
       }    
       @Override
       public void updateElement(UIElement element, @SuppressWarnings("rawtypes") Map map) {
           boolean condition = false;            
           //...            
           if( condition ) { 
               element.setIcon(image_disable);
           }else{
               element.setIcon(image_enable);
           }        
       }
   }
   

2. invoke this Handler using ICommandService:

       IWorkbenchWindow window = part.getSite().getWorkbenchWindow();
       ICommandService commandService = (ICommandService) window.getService(ICommandService.class);
       if (commandService != null) {
           commandService.refreshElements("com.packpub.e4.menu.commands.sampleCommand", null);
       }
   

Thanks.