Asynchronous Android

Table of Contents

Asynchronous Android

Credits

About the Author

About the Reviewers

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Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Downloading the example code

Errata

Piracy

Questions

1. Building Responsive Android Applications

Introducing the Dalvik Virtual Machine

Memory sharing and the Zygote

Understanding the Android thread model

The main thread

Unresponsive apps and the ANR dialog

Maintaining responsiveness

Concurrency in Android

Correctness issues in concurrent programs

Liveness issues in concurrent programs

Android-specific concurrency issues

The Activity lifecycle

Manipulating the user interface

Android-specific concurrency constructs

Summary

2. Staying Responsive with AsyncTask

Introducing AsyncTask

Declaring AsyncTask types

Executing AsyncTasks

Providing feedback to the user

Providing progress updates

Canceling AsyncTask

Handling exceptions

Controlling the level of concurrency

Common AsyncTask issues

Fragmentation issues

Activity lifecycle issues

Handling lifecycle issues with early cancellation

Handling lifecycle issues with retained headless fragments

Applications of AsyncTask

Summary

3. Distributing Work with Handler and HandlerThread

Understanding Looper

Building responsive apps with Handler

Scheduling work with post

Canceling a pending Runnable

Scheduling work with send

Canceling pending Messages

Composition versus Inheritance

Multithreaded example

Sending Messages versus posting Runnables

Building responsive apps with HandlerThread

Handler programming issues

Leaking implicit references

Leaking explicit references

Applications of Handler and HandlerThread

Summary

4. Asynchronous I/O with Loader

Introducing Loaders

Building responsive apps with AsyncTaskLoader

Building responsive apps with CursorLoader

Combining Loaders

Applications of Loaders

Summary

5. Queuing Work with IntentService

Introducing Service and IntentService

Building responsive apps with IntentService

Handling results

Returning results with PendingIntent

Posting results as system notifications

Applications of IntentService

HTTP uploads with IntentService

Reporting progress

Summary

6. Long-running Tasks with Service

Building responsive apps with Service

Controlling concurrency with Executors

Returning results with Messenger

Communicating with Services

Direct communication with local Services

Broadcasting results with Intents

Detecting unhandled broadcasts

Applications of Services

Summary

7. Scheduling Work with AlarmManager

Scheduling alarms with AlarmManager

Canceling alarms

Scheduling repeating alarms

Handling alarms

Handling alarms with Activities

Handling alarms with BroadcastReceiver

Doing work with BroadcastReceiver

Doing background work with goAsync

Handling alarms with Services

Staying awake with WakeLocks

Applications of AlarmManager

Summary

Index

Asynchronous Android

Asynchronous Android

Copyright © 2013 Packt Publishing

All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews.

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First published: December 2013

Production Reference: 1171213

Published by Packt Publishing Ltd.

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ISBN 978-1-78328-687-4

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Cover Image by Jarek Blaminsky (<[email protected]>)

Credits

Author

Steve Liles

Reviewers

David Bakin

Elie Abu Haydar

Hassan Makki

Matt Preston

Hélder Vasconcelos

Acquisition Editors

Harsha Bharwani

Kunal Parikh

Lead Technical Editor

Larissa Pinto

Technical Editors

Arwa Manasawala

Anand Singh

Proofreaders

Ameesha Green

Maria Gould

Copy Editors

Alisha Aranha

Mradula Hegde

Karuna Narayanan

Shambhavi Pai

Alfida Paiva

Lavina Pereira

Adithi Shetty

Project Coordinator

Jomin Varghese

Indexer

Hemangini Bari

Graphics

Yuvraj Mannari

Valentina D'silva

Production Coordinator

Manu Joseph

Cover Work

Manu Joseph

About the Author

Steve Liles is a self-confessed geek and has been an Android fan since the launch day of the G1. When he isn't at work building publishing systems and apps for newspapers and magazines, you'll find him tinkering with his own apps, building 3D printers, or playing RTS games. He is currently working with a start-up to build an advertising system that links the print and digital worlds using computer vision on Android and iOS devices.

I would like to sincerely thank the technical reviewers, who delivered their invaluable feedback gently and constructively. Without them, this book would be a pale shadow of the thing you now hold in your hands.

I once read that book acknowledgements are apologies to the people who have suffered. I must, therefore, unreservedly thank and apologize to my wife, not only for her patience and support during this project, but also through all the years and projects gone before.

About the Reviewers

David Bakin's first concurrent program was a Tektronix terminal emulator, written in assembly for an IMLAC PDS-1, which was a PDP-8-like machine with a GPU. He's written a lot of multiprocess and multithread concurrent programs and a number of tools for visualizing and debugging concurrent programs since then. He says computers now are orders of magnitude more powerful than the PDS-1, but concurrent programming hasn't gotten any easier.

His favorite languages are C++ and Haskell, and he prefers to use strong typing and functional programming techniques to write correct code. On the other hand, he also likes Smalltalk, Mathematica, and SIMD code in assembler because they're a lot of fun.

Elie Abu Haydar, born and raised in Beirut, has been interested in software development since his high school years. In 2006, he graduated from the American University of Science and Technology in Lebanon with a BS in Computer Science. As a software developer at KnowledgeView Ltd., Elie is seriously involved in every aspect of newsroom and publishing products where he uses Java to develop publishing solutions. These include backend web services and frontend web and mobile applications. Elie also contributes in the technical research and development of existing and future company projects.

Hassan Makki is a computer and communication engineer. He was born in 1979 in Lebanon and graduated in 2005. Since graduation, he has worked as a software engineer and has long-standing experience in C++, Java, and Android development. He began developing and managing Web and Android apps in 2011, and has developed around 30 apps related to news, music, sports, and advertisements.

Matt Preston is a professional software engineer with 14 years of experience in developing and maintaining a variety of systems for large international news and media organizations. He has worked on a range of low-latency/high-concurrency projects, ranging from mobile apps to distributed systems. Recently, he has been working on low-latency search and analytics using Elasticsearch.

I would like to thank my friend and colleague Steve Liles for this opportunity to let me review this book. We worked together for over 12 years and he's one of the best developers I have ever worked with. I learned a lot from him; I still continue to do so. Finally, thanks to Erica for all the tea; sorry about the late nights.

Hélder Vasconcelos has been a senior software engineer at Airtel ATN (Dublin, Ireland) since October 2012. He has extensive experience in designing and developing real-time/multithreaded Java and C/C++ applications for the telecommunications and aviation industry. Apart from his day-to-day job, for the last three years, he has been designing and developing native Android applications for Bearstouch Software and other third-party clients.

He graduated with a degree in Electronic & Telecommunications Engineering from the University of Aveiro in January 2006. He worked as a VoIP systems engineer at RedeRia Innovation (Aveiro, Portugal) from January 2006 to June 2007. He also worked as a software engineer at Outsoft/PT Inovação (Aveiro, Portugal) from October 2007 to October 2012.

Thanks to everyone involved in this project for your hard work and commitment, my awesome wife Tania for her love and support, and my parents and family for their awesome effort in my education. Additionally, I would like to thank my friends, colleagues, clients, and teachers for helping me to shape and improve my skills and perspectives during my career.

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Preface

Programming is the most fun a person can have on their own. This is a fact well-known to programmers, though it seems the rest of the world is yet to catch on. You already know this or you wouldn't be reading this book, but it constantly amazes me that more people aren't falling over themselves to learn to code.

Meanwhile, mobile devices have made computers fun even for non-coders. We carry in our pockets small machines with incredible processing power and a giddying array of sensors and interfaces.

Android takes these fun machines and makes them accessible to programmers through a fabulously well-crafted platform and tool chain, in a programming language that has stood the test of time yet continues to develop and evolve.

What could possibly be better than programming fun machines to do cool things, in a powerful language, on a well-crafted platform, with a world-class tool chain? For me, the answer is doing so with a good enough understanding of those things to make the difference between a good app and a great one.

There are many things that must come together to make a great app. You need a great idea—I can't help you there. You need a pretty user interface—sorry, wrong book. You need a great user experience—aha! Now we're getting somewhere. Among the many things that contribute to a great user experience, responsiveness is right up