How to create composite widgets using GWT?

In this tutorial, we will illustrate how to build composite widget using GWT. The steps involved in Building the Composite widgets are described below:-

First we need to declare label,TextBox,CheckBox,VerticalPanle as shown below:

Java Code: Code to declare the components

final Label label = new Label("Click the Node to view Tree structure")
private TextBox tb = new TextBox();
private CheckBox cb = new CheckBox();
VerticalPanel panel = new VerticalPanel()

We can add the checkbox to the panel using the panel.add(cb) method.The RootPanel.get().add(label1) method is used to add label to the rootpanel. Root panel is a panel to which all other widgets must be added. It is not created directly.

Java Code: Code to create a Composite widget using GWT

package org.widget.client;

import com.google.gwt.core.client.EntryPoint;
import com.google.gwt.user.client.ui.ClickListener;
import com.google.gwt.user.client.ui.Composite;
import com.google.gwt.user.client.ui.Label;
import com.google.gwt.user.client.ui.CheckBox;
import com.google.gwt.user.client.ui.RootPanel;
import com.google.gwt.user.client.ui.TextBox;
import com.google.gwt.user.client.ui.VerticalPanel;
import com.google.gwt.user.client.ui.Widget;

public class Compositewidgetex implements EntryPoint {

    private static class OptionalTextBox extends Composite
            implements ClickListener {

        private TextBox tb = new TextBox();
        private CheckBox cb = new CheckBox();

        public OptionalTextBox(String caption) {

            VerticalPanel panel = new VerticalPanel();
            panel.add(cb);
            panel.add(tb);

            cb.setText(caption);
            cb.setChecked(true);
            cb.addClickListener(this);
            initWidget(panel);
        }

        public void onClick(Widget sender) {
            if (sender == cb) {
                tb.setEnabled(cb.isChecked());
            }
        }

        public void setCaption(String caption) {
            cb.setText(caption);
        }

        public String getCaption() {
            return cb.getText();
        }
    }

    public void onModuleLoad() {
        final Label label =
                new Label("Example to show Composite widgets");
        final Label label1 =
                new Label("   ");
        OptionalTextBox optionalTextBox =
                new OptionalTextBox("Check this to enable");
        RootPanel.get().add(label);
        RootPanel.get().add(label1);
        RootPanel.get().add(optionalTextBox);

    }
}
Main

.gwt.xml
<?xml version="1.0" encoding="UTF-8"?>
<module>
  <inherits name="com.google.gwt.user.User"/>
  <entry-point class  

="org.widget.client.Compositewidgetex"/>
  
</module>

Output of the program