Menu Contributions/Update checked state

Update the toolbar item checked state

The active handler can update any UI elements registered against the its command. It does this by requesting the ICommandService to refresh any registered UIElements.

As a handler becomes active and implement IElementUpdater like org.eclipse.ui.tests.menus.ToggleContextHandler, the command service calls public void updateElement(UIElement element, Map parameters) for every UIElement registered against the command.

public class ToggleContextHandler extends AbstractHandler implements
    IElementUpdater {
  private static final String TOGGLE_ID = "toggleContext.contextId";
  // ...
  public void updateElement(UIElement element, Map parameters) {
    // the checked state depends on if we have an activation for that
    // context ID or not
    String contextId = (String) parameters.get(TOGGLE_ID);
    element.setChecked(contextActivations.get(contextId) != null);
  }
}