Elements of a TouchKit Application

At minimum, a TouchKit application requires a UI class, which is defined in a deployment descriptor, as usual for Vaadin applications. You usually define a servlet class, where you can also do some TouchKit-specific configuration. You may also need to have a custom theme. These and other tasks are described in the following subsections.

The Servlet Class

When using a Servlet 3.0 compatible application server, you usually define the UI and make basic configuration with a servlet class with the @WebServlet annotation. Vaadin Plugin for Eclipse creates the servlet class as a static inner class of the UI class, while the Maven archetype creates it as a separate class, which is usually the preferred way.

The servlet class must define the UI class as usual. Additionally, you can configure the following TouchKit features in the servlet class:

  • Customize bookmark or home screen icon

  • Customize splash screen image

  • Customize status bar in iOS

  • Use special web app mode in iOS

  • Provide a fallback UI ( "Providing a Fallback UI")

  • Enable offline mode

A custom servlet should normally extend the TouchKitServlet. You should place your code in servletInitialized() and call the super method in the beginning.

public class MyServlet extends TouchKitServlet {
    protected void servletInitialized() throws ServletException {

        ... customization ...

If you need to rather extend some other servlet, possibly in another add-on, it should be trivial to reimplement the functionality of TouchKitServlet, which is just to manage the TouchKit settings object.

If using web.xml deployment descriptor instead of the @WebServlet, you only need to implement custom servlet class if you need to do any of the above configuration, which you typically need to do.

Defining Servlet and UI with web.xml Deployment Descriptor

If using an old style web.xml deployment descriptor, you need to define the special TouchKitServlet class instead of the regular VaadinServlet in the web.xml deployment descriptor. Often you need to make some configuration or add special logic in a custom servlet, as described in the previous section, in which case you need to define your servlet in the deployment descriptor.

  <servlet-name>Vaadin UI Servlet</servlet-name>
    <description>Vaadin UI class to start</description>

TouchKit Settings

TouchKit has a number of settings that you can customize for your needs. The TouchKitSettings configuration object is managed by TouchKitServlet, so if you make any modifications to it, you need to implement a custom servlet, as described earlier.

public class MyServlet extends TouchKitServlet {
    protected void servletInitialized() throws ServletException {

        TouchKitSettings s = getTouchKitSettings();

The settings include special settings for iOS devices, which are contained in a separate IosWebAppSettings object, available from the TouchKit settings with getIosWebAppSettings().

Application Icons

The location bar, bookmarks, and other places can display an icon for the web application. You can set the icon, or more exactly icons, in an ApplicationIcons object, which manages icons for different resolutions. The most properly sized icon for the context is used. iOS devices prefer icons with 57×57, 72×72, and 144×144 pixels, and Android devices 36×36, 48×48, 72×72, and 96×96 pixels.

You can add an icon to the application icons collection with addApplicationIcon(). You can acquire the base URL for your application from the servlet context, as shown in the following example.

TouchKitSettings s = getTouchKitSettings();
String contextPath = getServletConfig()
    contextPath + "VAADIN/themes/mytheme/icon.png");

The basic method just takes the icon name, while the other one lets you define its size. It also has a preComposed parameter, which when true, instructs Safari from adding effects to the icon in iOS.

Viewport Settings

The ViewPortSettings object, which you can get from the TouchKit settings with getViewPortSettings(), manages settings related to the display, most importantly the scaling limitations.

TouchKitSettings s = getTouchKitSettings();
ViewPortSettings vp = s.getViewPortSettings();

See the Safari Development Library at the Apple developer’s site for more details regarding the functionality in the iOS browser.

Startup Image for iOS

iOS browser supports a startup (splash) image that is shown while the application is loading. You can set it in the IosWebAppSettings object with setStartupImage(). You can acquire the base URL for your application from the servlet context, as shown in the following example.

TouchKitSettings s = getTouchKitSettings();
String contextPath = getServletConfig().getServletContext()
    contextPath + "VAADIN/themes/mytheme/startup.png");

Web App Capability for iOS

iOS supports a special web app mode for bookmarks added and started from the home screen. With the mode enabled, the client may, among other things, hide the browser’s own UI to give more space for the web application. The mode is enabled by a header that tells the browser whether the application is designed to be used as a web application rather than a web page.

TouchKitSettings s = getTouchKitSettings();

See the Safari Development Library at the Apple developer’s site for more details regarding the functionality in the iOS browser.

Cache Manifest

The ApplicationCacheSettings object manages the cache manifest, which is used to configure how the browser caches the page and other resources for the web app. See "Offline Mode" for more details about its use.

The UI

Mobile UIs extend the UI class as usual and construct the user interface from components.

@Title("My Simple App")
public class SimplePhoneUI extends UI {
    protected void init(VaadinRequest request) {
        // Create the content root layout for the UI
        TabBarView mainView = new TabBarView();


As TouchKit comes with a custom widget set, you need to use a combining widget set for your project, defined with the @Widgetset annotation for the UI. The combining widget set descriptor is automatically generated by the Vaadin Plugin for Eclipse and in Maven when you install or define the TouchKit add-on.

Most commonly, you will use a combination of the major three TouchKit components as the basis of the UI: TabBarView, NavigationView, or NavigationManager.

If a offline UI is provided, it needs to be enabled in the initialization of the UI, as described in "Offline Mode". This code is included in the project stub created by the Maven archetype.

Mobile Widget Set

TouchKit includes a widget set and therefore requires compiling a project widget set that includes it, as described in "Using Vaadin Add-ons". The project widget set descriptor is automatically generated during the compilation process, whether you use Maven or the Eclipse plugin.

Note that if you have a TouchKit UI in the same project as a non-TouchKit UI, you probably do not want to compile the TouchKit widget set into its widget set. As the automatic generation of the descriptor includes all the widget sets that it finds from the class path, the result can be unwanted, and you need to edit the widget set descriptor manually.

Mobile Theme

You can use both Sass and CSS themes for TouchKit applications, although they are defined a bit differently from regular Vaadin themes. To optimize how a theme is loaded, you can build it into a GWT client bundle.

Defining a Regular Theme

Using plain CSS is often the easiest way to define a simple theme for a mobile application, as using Sass would not yield all the same benefits as in a regular Vaadin application. TouchKit includes its own base theme in its widget set, so you do not need to @import it explicitly.

A CSS theme is defined in a file located at VAADIN/themes/mymobiletheme/styles.css. As importing the base does not need to (and should not) be done, it could simply be as follows:

.stylishlabel {
    color: red;
    font-style: italic;

You need to set the theme with the @Theme("mymobiletheme") annotation for your UI class, as usual.

You can also use Sass by creating a styles.scss and then compiling it to CSS with the Vaadin theme compiler. However, as above, you should not include a base theme. The rules do not need to be wrapped in a selector with the theme name, as is recommended for regular Vaadin themes.

Responsive Mobile Themes

The responsive extension is especially useful for mobile layouts, as it makes it easy to adapt a layout for phones and tablets and for changing the screen orientation. With the extension, changing the UI layout according to screen orientation is handled entirely on the client-side by the add-on, using special CSS selectors in the theme. See "Responsive Themes" for details.

The Parking Demo uses the extension. From its source code, which is available at Github, you can learn how the conditional selectors are used in the CSS defined in a GWT client bundle.

For example, the CSS for the Stats tab in the Parking demo defines a responsive selector as follows, to allow fitting two charts side-by-side if there is enough room horizontally:

.stats .statschart {
    margin-bottom: 30px;
    float: left;
    width: 100%;

.v-ui[width-range~="801px-"] .stats .statschart {
    width: 48% !important;
    margin: 0 1%;

Normally, if there’s 800 pixels or less space horizontally, each chart takes 100% of the screen width, causing the second one to wrap to the next line in the containing CssLayout. If there is more space, the two charts are shown in 48% width, so that both can fit in the same line.

This follows the flexible wrapping pattern described in "Flexible Wrapping".

Defining a Theme in a GWT Client Bundle

Using a GWT theme instead of a regular Vaadin theme offers several performance benefits on mobile devices by reducing the number of resources loaded separately. All the resources, such as images and stylesheets, can be loaded with the widget set. Images can be handled as sprites tiled in bundle images.

The GWT CSS classes have their own special format, a bit similar to Sass themes. See GWT Developer’s Guide for detailed information about client bundles and how to define image, CSS, and other resources.

To use a GWT client bundle in a TouchKit application, you need to define a theme loader that extends the TouchKit ThemeLoader and implements the load() method to inject the bundle. The theme loader and the client bundle are a client-side classes that are compiled into the widget set, and must therefore be defined under the client directory.

For example, in the Parking Demo we have as follows:

public class ParkingThemeLoader extends ThemeLoader {
    public final void load() {
        // First load the default TouchKit theme...

        // ... and add Parking Demo CSS from its own bundle

You can call super.load() to load the default TouchKit theme, but you can omit the call if you do not want to use it. In such case, your GWT theme should import the Vaadin base theme explicitly.

The theme loader must be defined in the .gwt.xml widget set descriptor as follows:

        class="com.vaadin.addon.touchkit.gwt.client.ThemeLoader" />

See the Parking Demo sources for a complete example of defining a GWT theme.

Using Font Icons

You can use font icons, as described in "Font Icons", also with most TouchKit components.

Font Icons in TabBarView

For example, as is done in the UI stub of a TouchKit project created from the Maven archetype:

// Have a tab bar with multiple tab views
TabBarView tabBarView = new TabBarView();

// Have a tab
... create view1 ...
Tab tab1 = tabBarView.addTab(view1);

// Use the "book" icon for the tab