Book Image

Ext GWT 2.0: Beginner's Guide

By : Daniel Vaughan
Book Image

Ext GWT 2.0: Beginner's Guide

By: Daniel Vaughan

Overview of this book

<p>Ext GWT, also known as GXT, takes Google Web Toolkit one step further by providing a wide range of powerful user interface components. It allows a developer to create powerful web applications that are almost like desktop applications. However to leverage all the features of this powerful Java library for creating desktop-style web applications, you need to learn how and when to use the right user interface component.<br /><br />Ext GWT 2.0: Beginner's Guide is a practical book that teaches you how to use the EXT GWT library to its full potential. It provides a thorough and no-nonsense explanation of the Ext GWT library, what it offers and how to use it through practical examples. This book provides clear, step-by-step instructions for getting the most out of Ext GWT and offers practical examples and techniques that can be used for building your own applications in EXT GWT<br /><br />This book gets you up and running instantly to build powerful Rich Internet Applications (RIA) with Ext GWT. It then takes you through all the interface-building widgets and components of Ext GWT using practical examples to demonstrate when, where, and how to use each of them. Layouts, forms, panels, grids, trees, toolbars, menus, and many other components are covered in the many examples packed in this book. You will also learn to present your data in a better way with templates and use some of the most sought-after features of Ext GWT in your web applications such as drag-and-drop and charts. Throughout the book a real application is built step by step using Ext GWT and deployed to Google App Engine.</p> <p>Imagine how great you'll feel when you're able to create great-looking desktop-style user interfaces for your web applications with Ext GWT!</p>
Table of Contents (17 chapters)
Ext GWT 2.0 Beginner's Guide
Credits
About the Author
About the Reviewers
Preface
Index

GXT building block 3: Events


Events are the concepts used for informing the program that something has happened. This can be the user interacting in some way with the application such as clicking on a button or the state of a component changing. Each action causes an event to be fired and gives any component that is listening for the event the opportunity to respond.

More formally, this is known as the observer pattern. In GXT, listeners can be added to components so that when an event is fired, any listeners are notified and can handle the event.

The base class for event is com.extjs.gxt.ui.client.event.BaseEvent and GXT provides a wide range of events. We will cover a few of these later in this chapter and many more in later chapters.

Sinking and swallowing events

As part of GWT's design, widgets respond to some, but not all browser events, and this also applies to GXT. The reason for this is to keep memory usage down and to avoid memory leaks. If a widget needs to respond to a browser event...