Create GXT 3 project example

Here is the way you could create GXT 3 project.
You would use Maven Archetype with a little workaround of pom.xml and code.

Form CLI execute:

mvn archetype:generate    -DarchetypeGroupId=org.codehaus.mojo    -DarchetypeArtifactId=gwt-maven-plugin    -DarchetypeVersion=2.7.0

Then:

mvn gwt:verify

mvn gwt:run

At this point you will be able to run pure GWT demo.

Now is the GXT time:

In root html file add following line as the first stylesheet

<link rel="stylesheet" type="text/css" href="MyModule/reset.css">

Remove the table for the Web Application Starter project. We don’t need it for this guide.

Add the line below to the *.gwt.xml
<inherits name="com.sencha.gxt.ui.GXT" />
And remove the following line from the same file:
<inherits name="com.google.gwt.user.theme.standard.Standard" />

Inside of the main root class that implements EntryPoint leave only this:

public void onModuleLoad() {
    BasicTabExample tabs = new BasicTabExample();
    RootPanel.get().add(tabs);
}

Create in the same package of the root class this class:

import com.google.gwt.event.logical.shared.SelectionEvent;

import com.google.gwt.event.logical.shared.SelectionHandler;

import com.google.gwt.user.client.ui.HTML;

import com.google.gwt.user.client.ui.Label;

import com.google.gwt.user.client.ui.VerticalPanel;

import com.google.gwt.user.client.ui.Widget;

import com.sencha.gxt.widget.core.client.PlainTabPanel;

import com.sencha.gxt.widget.core.client.TabItemConfig;

import com.sencha.gxt.widget.core.client.TabPanel;

import com.sencha.gxt.widget.core.client.container.FlowLayoutContainer;

import com.sencha.gxt.widget.core.client.info.Info;

public class BasicTabExample extends FlowLayoutContainer {

    public BasicTabExample() {

        VerticalPanel vp = new VerticalPanel();

        vp.setSpacing(10);

        String txt = "Test";

        SelectionHandler<Widget> handler = new SelectionHandler<Widget>() {

          public void onSelection(SelectionEvent<Widget> event) {

            TabPanel panel = (TabPanel) event.getSource();

            Widget w = event.getSelectedItem();

            TabItemConfig config = panel.getConfig(w);

            Info.display("Message", "'" + config.getText() + "' Selected");

          }

        };

        TabPanel folder = new TabPanel();

        folder.addSelectionHandler(handler);

        folder.setWidth(450);

        HTML shortText = new HTML(txt);

        shortText.addStyleName("pad-text");

        folder.add(shortText, "Short Text");

        HTML longText = new HTML(txt + "<br><br>" + txt);

        longText.addStyleName("pad-text");

        folder.add(longText, "Long Text");

        final PlainTabPanel panel = new PlainTabPanel();

        panel.setPixelSize(450, 250);

        panel.addSelectionHandler(handler);

        Label normal = new Label("Just a plain old tab");

        normal.addStyleName("pad-text");

        panel.add(normal, "Normal");

        Label iconTab = new Label("Just a plain old tab with an icon");

        iconTab.addStyleName("pad-text");

        TabItemConfig config = new TabItemConfig("Icon Tab");

        panel.add(iconTab, config);

        Label disabled = new Label("This tab should be disabled");

        disabled.addStyleName("pad-text");

        config = new TabItemConfig("Disabled");

        config.setEnabled(false);

        panel.add(disabled, config);

        vp.add(folder);

        vp.add(panel);

        add(vp);

        }

}