50 Android Hacks

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ISBN 9781617290565

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Dedication

Al milagro que hizo esto posible

(To the miracle that made this possible)

Brief Table of Contents

Copyright

Brief Table of Contents

Table of Contents

Foreword

Preface

Acknowledgments

About this Book

About the Cover Illustration

Chapter 1. Working your way around layouts

Chapter 2. Creating cool animations

Chapter 3. View tips and tricks

Chapter 4. Tools

Chapter 5. Patterns

Chapter 6. Working with lists and adapters

Chapter 7. Useful libraries

Chapter 8. Interacting with other languages

Chapter 9. Ready-to-use snippets

Chapter 10. Beyond database basics

Chapter 11. Avoiding fragmentation

Chapter 12. Building tools

Index

List of Figures

Table of Contents

Copyright

Brief Table of Contents

Table of Contents

Foreword

Preface

Acknowledgments

About this Book

About the Cover Illustration

Chapter 1. Working your way around layouts

Hack 1 Centering views using weights: Android v1.6+

1.1. Combining weightSum and layout_weight

1.2. The bottom line

1.3. External links

Hack 2 Using lazy loading and avoiding replication: Android v1.6+

2.1. Avoid replication using the tag

2.2. Lazy loading views with the ViewStub class

2.3. The bottom line

2.4. External links

Hack 3 Creating a custom ViewGroup: Android v1.6+

3.1. Understanding how Android draws views

3.2. Creating the CascadeLayout

3.3. Adding custom attributes to the children

3.4. The bottom line

3.5. External links

Hack 4 Preferences hacks: Android v1.6+

4.1. The bottom line

4.2. External links

Chapter 2. Creating cool animations

Hack 5 Snappy transitions with TextSwitcher and ImageSwitcher: Android v1.6+

5.1. The bottom line

5.2. External links

Hack 6 Adding eye candy to your ViewGroup’s children: Android v1.6+

6.1. The bottom line

6.2. External links

Hack 7 Doing animations over the Canvas: Android v1.6+

7.1. The bottom line

7.2. External links

Hack 8 Slideshow using the Ken Burns effect: Android v1.6+

8.1. The bottom line

8.2. External links

Chapter 3. View tips and tricks

Hack 9 Avoiding date validations with an EditText for dates: Android v1.6+

9.1. The bottom line

9.2. External links

Hack 10 Formatting a TextView’s text: Android v1.6+

10.1. The bottom line

10.2. External links

Hack 11 Adding text glowing effects: Android v1.6+

11.1. The bottom line

11.2. External links

Hack 12 Rounded borders for backgrounds: Android v1.6+

12.1. The bottom line

12.2. External links

Hack 13 Getting the view’s width and height in the onCreate() method: Android v1.6+

13.1. The bottom line

13.2. External links

Hack 14 VideoViews and orientation changes: Android v1.6+

14.1. The bottom line

14.2. External links

Hack 15 Removing the background to improve your Activity startup time: Android v1.6+

15.1. The bottom line

15.2. External links

Hack 16 Toast’s position hack: Android v1.6+

16.1. The bottom line

16.2. External links

Hack 17 Creating a wizard form using a Gallery: Android v2.1+

17.1. The bottom line

17.2. External links

Chapter 4. Tools

Hack 18 Removing log statements before releasing: Android v1.6+

18.1. The bottom line

18.2. External links

Hack 19 Using the Hierarchy Viewer tool to remove unnecessary views: Android v1.6+

19.1. The bottom line

19.2. External links

Chapter 5. Patterns

Hack 20 The Model-View-Presenter pattern: Android v1.6+

20.1. The bottom line

20.2. External links

Hack 21 BroadcastReceiver following Activity’s lifecycle: Android v1.6+

21.1. The bottom line

21.2. External links

Hack 22 Architecture pattern using Android libraries: Android v1.6+

22.1. Back-end logic and model

22.2. Android library

22.3. Android application

22.4. The bottom line

22.5. External links

Hack 23 The SyncAdapter pattern: Android v2.2+

23.1. Common approaches

23.2. What we’ll create

23.3. The bottom line

23.4. External links

Chapter 6. Working with lists and adapters

Hack 24 Handling empty lists: Android v1.6+

24.1. The bottom line

24.2. External links

Hack 25 Creating fast adapters with a ViewHolder: Android v1.6+

25.1. The bottom line

25.2. External links

Hack 26 Adding section headers to a ListView: Android v1.6+ Contributed by Chris King

26.1. Creating list layouts

26.2. Providing visible section headers

26.3. Wrapping up

26.4. The bottom line

26.5. External links

Hack 27 Communicating with an Adapter using an Activity and a delegate: Android v1.6+

27.1. The bottom line

27.2. External links

Hack 28 Taking advantage of ListView’s header: Android v1.6+

28.1. The bottom line

28.2. External links

Hack 29 Handling orientation changes inside a ViewPager: Android v1.6+

29.1. The bottom line

29.2. External links

Hack 30 ListView’s choiceMode: Android v1.6+

30.1. The bottom line

30.2. External links

Chapter 7. Useful libraries

Hack 31 Aspect-oriented programming in Android: Android v1.6+

31.1. The bottom line

31.2. External links

Hack 32 Empowering your application using Cocos2d-x: Android v2.2+

32.1. What is Cocos2d-x?

32.2. Using Cocos2d-x

32.3. The bottom line

32.4. External links

Chapter 8. Interacting with other languages

Hack 33 Running Objective-C in Android: Android v1.6+

33.1. Downloading and compiling Itoa

33.2. Creating the modules

33.3. Setting up the Java part

33.4. The bottom line

33.5. External links

Hack 34 Using Scala inside Android: Android v1.6+

34.1. The bottom line

34.2. External links

Chapter 9. Ready-to-use snippets

Hack 35 Firing up multiple intents: Android v2.1+

35.1. Taking a picture

35.2. Picking a picture from the gallery

35.3. Mixing both intents

35.4. The bottom line

35.5. External links

Hack 36 Getting user information when receiving feedback: Android v1.6+

36.1. The bottom line

36.2. External links

Hack 37 Adding an MP3 to the media ContentProvider: Android v1.6+

37.1. Adding the MP3 using content values

37.2. Adding the MP3 using the media scanner

37.3. The bottom line

37.4. External links

Hack 38 Adding a refresh action to the action bar: Android v2.1+

38.1. The bottom line

38.2. External links

Hack 39 Getting dependencies from the market: Android v1.6+

39.1. The bottom line

39.2. External links

Hack 40 Last-in-first-out image loading: Android v2.1+ Contributed by William Sanville

40.1. Starting point: Android sample application

40.2. Introducing executors

40.3. UI thread—leaving and returning seamlessly

40.4. Considerations

40.5. The bottom line

40.6. External links

Chapter 10. Beyond database basics

Hack 41 Building databases with ORMLite: Android v2.2+ Contributed by William Sanville

41.1. A simple data model

41.2. Getting started

41.3. Rock-solid database schema

41.4. SQLiteOpenHelper—your gateway to the database

41.5. Singleton pattern for database access

41.6. CRUD operations made easy

41.7. Query builders

41.8. Data types and tricky foreign types

41.9. Raw SQL queries

41.10. Transactions

41.11. The bottom line

41.12. External links

Hack 42 Creating custom functions in SQLite: Android v1.6+

42.1. Java code

42.2. Native code

42.3. The bottom line

42.4. External links

Hack 43 Batching database operations: Android v2.1+

43.1. No batch

43.2. Using batch operations

43.3. Applying batch using SQLiteContentProvider

43.4. The bottom line

43.5. External links

Chapter 11. Avoiding fragmentation

Hack 44 Handling lights-out mode: Android v1.6+

44.1. Android 2.x

44.2. Android 3.x

44.3. Merging both worlds in a single Activity

44.4. The bottom line

44.5. External links

Hack 45 Using new APIs in older devices: Android v1.6+

45.1. Using apply() instead of commit()

45.2. Storing the app on the SD card

45.3. The bottom line

45.4. External links

Hack 46 Backward-compatible notifications: Android v1.6+

46.1. The bottom line

46.2. External links

Hack 47 Creating tabs with fragments: Android v1.6+

47.1. Creating our tab UI

47.2. Placing the tabs in an Activity

47.3. The bottom line

47.4. External links

Chapter 12. Building tools

Hack 48 Handling dependencies with Apache Maven: Android v1.6+

48.1. The bottom line

48.2. External links

Hack 49 Installing dependencies in a rooted device: Android v1.6+

49.1. Predexing

49.2. Creating the permissions XML

49.3. Modifying AndroidManifest.xml

49.4. The bottom line

49.5. External links

Hack 50 Using Jenkins to deal with device diversity: Android v1.6+ Contributed by Christopher Orr

50.1. Creating a Jenkins job

50.2. Running the job

50.3. The bottom line

50.4. External links

Index

List of Figures

Foreword

Android as an ecosystem is expanding rapidly in all directions. Every day manufacturers introduce new devices and form factors, consumers purchase and activate over one million devices, and users download and try new apps. It’s the job of developers (yourself included, hopefully) to fill this ecosystem with beautiful, engaging, and deeply fulfilling applications through which users can better interpret and interact with their world.

As a platform, Android was birthed in late 2003 by former employees of Danger (the company behind the popular Sidekick phones). In 2005 the company driving Android was acquired by Google, and three years later the HTC Dream (G1) was released as the first consumer device running Android. Over the next three years the hardware and platform were heavily iterated, but Android remained solely a phone operating system.

In 2011 Google introduced two new form factors for the Android: tablets and TV. This represented the first official deviation from phones as the device of choice and sparked manufacturer interest in other devices. Android now runs on laptops, wrist-watches, video game consoles, and car stereos. It can only be expected that in the future the number of devices supporting Android will continue to grow.

As application developers, it’s extremely important that you understand the diversity of the platform and the direction in which it’s heading. Creating content on Android is no longer as simple as designing for a phone-sized screen held in portrait orientation. While this does mean more work for the developer creating apps, the end result is a vastly more pleasant experience for the user, regardless of which device your content is consumed on.

In developing applications there are three major things that you’ll need aside from your own creativity and desire to develop: the platform documentation, the open source community, and glue to hold everything together. The platform documentation is easy, since the latest version is always hosted at http://developer.android.com. The open source community is spread across GitHub, Google Code, Stack Overflow, and the like, providing libraries, code snippets, and design patterns for simplifying development. You still need something to tie these disjointed pieces together as one cohesive app. If it were as simple as arranging a few building blocks, everyone would be developing applications. This book is that glue.

Contained in the book are examples of how to solve common problems that arise in Android development. Some are relatively trivial and some quite complex. What they share, however, is being loosely or sparsely documented facets of app development which often cause developers pain. 50 Android Hacks is not meant as a sole resource for learning or mastering Android development, but rather exists to fill in the cracks.

It’s a great task to craft an app that’s dynamic enough to support Android’s growing device diversity. With the knowledge provided by this book, accompanied by that of similar print and online sources, it’s my hope that you’re more empowered to develop and publish apps. Beyond this, while I am a developer just like you, I am also an avid Android user and patiently await that next great application. Perhaps you will be the one to write it.

JAKE WHARTON

ANDROID ENGINEER

Preface

I started learning about Android back in 2009. Android version 1.5 had just been released, and it showed a lot of potential.

In July 2009, thanks to a friend living in Australia, I got my first Android-powered device, an HTC Magic with Android version 1.5. To be honest, it processed more slowly than I expected, but I started testing the APIs and creating apps that I wanted to have on my cell phone. I sensed that Android would get a lot of attention and I knew that if I managed to create an application, it would be available to a lot of people.

I was proved right—not long afterward, there was a kick-off for Android development, which soon grew bigger and bigger. Suddenly a lot of tools and third-party libraries supporting the Android platform emerged—everything from game frameworks, like cocos2d-x, to build systems, like Apache Maven.

In November 2010 I was asked to review a book from Manning Publications called Android in Practice (www.manning.com/collins/). Delving deep into Manning’s work, it occurred to me that I could write a book about Android development using a different approach. I wanted to imitate Joshua Bloch’s Effective Java (www.amazon.com/Effective-Java-2nd-Joshua-Bloch/dp/0321356683), providing tips and patterns I had learned over all my years of developing for the Android platform.

Essentially, I wanted to gather together in one book every Android tip I have learned and provide some degree of documentation for it. That’s what 50 Android Hacks is all about: a collection of tips gathered in the process of developing different Android applications.

Something I enjoyed about Effective Java was that the book doesn’t have any particular order and I could read various sections, learning something different from each of them. After some time, I would go back to the book and find a different application for the project I was working on. I kept that in mind while writing this book. I imagine the reader investigating a hack while going to work or before going to sleep, getting new ideas for the project they’re working on.

I’m already using this book on my new projects, copying the sample code for certain tasks and using its examples to explain to my coworkers certain patterns.