Book Image

Hands-On Android UI Development

By : Jason Morris
Book Image

Hands-On Android UI Development

By: Jason Morris

Overview of this book

A great user interface (UI) can spell the difference between success and failure for any new application. This book will show you not just how to code great UIs, but how to design them as well. It will take novice Android developers on a journey, showing them how to leverage the Android platform to produce stunning Android applications. Begin with the basics of creating Android applications and then move on to topics such as screen and layout design. Next, learn about techniques that will help improve performance for your application. Also, explore how to create reactive applications that are fast, animated, and guide the user toward their goals with minimal distraction. Understand Android architecture components and learn how to build your application to automatically respond to changes made by the user. Great platforms are not always enough, so this book also focuses on creating custom components, layout managers, and 2D graphics. Also, explore many tips and best practices to ease your UI development process. By the end, you'll be able to design and build not only amazing UIs, but also systems that provide the best possible user experience.
Table of Contents (21 chapters)
Title Page
Credits
About the Author
About the Reviewers
www.PacktPub.com
Customer Feedback
Preface
13
Activity Lifecycle

Multiple event listeners


Unlike many other event systems, however, many Android components only allow a single event listener of certain types; this diverges from platforms such as Java desktop, or JavaScript in the browser, where any number of click listeners can be attached to a single element. In Android, click listeners are almost always set rather than added.

Note

This is actually a clever tradeoff--having multiple listeners for each event means that you need at least an array of them; the array needs to be sized and copied when it runs out of space, while it's actually very seldom that multiple listeners are needed. Multiple listeners also means that the widgets must traverse the list every time they want to dispatch events, so sticking to a single listener simplifies the code, and reduces the amount of required memory.

If you ever find yourself needing more than one listener for an event and widget that only provides a single listener slot, simply write a simple delegate class, like...