Demo problem on site Vaadin

Hello,
I tried to create a new component with eht example on the site VAADIN, but there is a problem on the ok button:

http://demo.vaadin.com/sampler/#ui/layout/custom-layout

The button is just a label, not a real button, when i click on it, nothing happens, is it normal?

UI:

VerticalLayout layout = new VerticalLayout();
        layout.setMargin(true);
        setContent(layout);
        
        Panel panel = new Panel("Login");
        panel.setSizeUndefined();
        layout.addComponent(panel);
        
        CustomLayout sample = new CustomLayout("mylayout");
        panel.setContent(sample);
        TextField username = new TextField();
        sample.addComponent(username, "username");


        TextField password = new TextField();
        sample.addComponent(password, "password");


        [b]
Button ok = new Button("Login");
[/b]
        [b]
sample.addComponent(ok, "okbutton");
[/b]

HTML:

<!--This CustomLayout uses inline styles.-->
<table align="center" cellspacing="10"
    style="width: 100%; height: 100%; color: #fff; padding: 20px;
    background: #31629E repeat-x">
    <tr>
        <td colspan="2">
        <h1 style="margin-top: 0;">Login</h1>
        <td>
    </tr>
    <tr>
        <td align="right">User name:</td>
        <td>
        <div location="username"></div>
        </td>
    </tr>
    <tr>
        <td align="right">Password:</td>
        <td>
        <div location="password"></div>
        </td>
    </tr>
    <tr>
        <td align="right" colspan="2">
        <div location="[b]
okbutton
[/b]" style="padding: 10px;"></div>
        </td>
    </tr>
    <tr>
        <td colspan="2" style="padding: 7px; background-color: #4172AE">
        <span style="font-family: FontAwesome; margin-right: 5px;">&#xf05a;</span>
        This information is in the layout.
        <td>
    </tr>
</table>

Sorry, the click event works when i add the listener, but how can i show it as a button?

The “Login” button in the example has apparently been styled to look like text in the application’s theme.

And yes, the example doesn’t include a listener for the button, so it doesn’t do anything.