Question

I would like to implement menus (MenuBar, MenuItem) using the declarative approach via UiBinder in GWT 2.0.

I have run into two problems:

1. Is there a way to add MenuItemSeparators in the .ui.xml file? So
   far, I have only managed to put MenuBar- and MenuItem-tags into the
   file.

2. Using @UiHandler, GWT writes the boilerplate code for event
   handlers for me. For menus, I need to write commands. How am I
   supposed to do this using the UiBinder approach? Is there a command
   tag to put in the .ui.xml file? Do I have to write the boilerplate
   code for the command handlers myself?

Thanks for thinking about these questions!

Answer 1

I agree, if you try to put a MenuItemSeparator in, it will complain stating only a MenuItem can be a child when GWT tries to create the widget . Since this is not currently supported, I suggest that you request this as a future enhancement to the GWT team.

In the meantime, you can add a separator programmatically and add a command in the following manner:
The XML file:

<ui:UiBinder xmlns:ui="urn:ui:com.google.gwt.uibinder" xmlns:g="urn:import:com.google.gwt.user.client.ui">
<g:HTMLPanel>
    <g:MenuBar ui:field="menuBar">
        <g:MenuItem ui:field="helpMenuItem">Help</g:MenuItem>
        <g:MenuItem ui:field="aboutMenuItem">About</g:MenuItem>
        <g:MenuItem ui:field="siteMapMenuItem">Site Map</g:MenuItem>
    </g:MenuBar>
</g:HTMLPanel>

The Java file(s):

public class Menu extends Composite {
...
@UiField MenuBar menuBar;
@UiField MenuItem helpMenuItem;
...
public Menu() {
    initWidget(uiBinder.createAndBindUi(this));
    // insert a separator
    menuBar.insertSeparator(1);
    // attach commands to a menu item
    helpMenuItem.setCommand(new MenuCommand(HistoryToken.Help));
    ...
}  

public class MenuCommand implements Command {
    final HistoryToken historyToken;

    public MenuCommand(HistoryToken historyToken) {
        this.historyToken = historyToken;
    }

    @Override
    public void execute() {
        historyToken.fire();
    }
}  

public enum HistoryToken {
    Help,About,SiteMap;

    public void fire(){
        History.newItem(this.toString());
    }
}

Elsewhere in my code, I implemented a HistoryListener to catch any changes, i.e.

class HistoryManager implements ValueChangeHandler<String> {
    // 1. get token
    // 2. change it into a HistoryToken
    // 3. perform switch statement 
    // 4. change contents based upon HistoryToken found
...
}