a deep dive into open source android development

A Deep Dive into Open Source Android

DevelopmentDavid Wu@wuman

blog.wu-man.com

Taipei Google Technology User Group (2013/01/02)

Taipei Open Source Software User Group (2012/12/18)

元智大學資工學系 開放源碼於行動終端之發展講座 (2012/12/07)

1

about.me/wuman2

Overview

• Why use open source?

• Popular open source Android libraries

• Why open source?

• How to open source

• Conclusion

3

Why use open source?

4

Better Quality

• Developed by many passionate developers

• Innovation and enhancements over time

• Improvements and bug fixes by more people

• Closest to user needs

5

Freedom

• Make custom changes to tailor to own needs

• Good open source software usually adheres to open standards and promotes interoperability

6

Learn from the Masters

• Open source developers are usually good at what they do

• The fastest way to improve is to learn from reading their code

• Discussions are usually carried out in the open via mailing lists

7

Not Possible Otherwise

• It is much harder to develop an Android app without using open source software

• Platform compatibility

• UI compatibility

8

Android app development is

NOT easy!

9

Apps targeting the widest audience need to care about platform compatibility

Jelly Bean

Ice Cream Sandwich

HoneycombGingerbread

Froyo

Eclair & olderVersion Codename API Distribution

1.5 Cupcake 3 0.1%

1.6 Donut 4 0.3%

2.1 Eclair 7 2.7%

2.2 Froyo 8 10.3%

2.3 - 2.3.2Gingerbread

9 0.2%

2.3.3 - 2.3.7Gingerbread

10 50.6%

3.1Honeycomb

12 0.4%

3.2Honeycomb

13 1.2%

4.0.3 - 4.0.4 Ice Cream Sandwich 15 27.5%

4.1Jelly Bean

16 5.9%

4.2Jelly Bean

17 0.8%

10

UI Requirements for Featured Apps

• Follow Android Design guidelines

• Navigation

• Action Bar

• Use common UI patterns and icons

11

Action Bar Incompatibility

• Before 3.0, there was no common pattern or API for in-app navigation.

• Action Bar API and pattern guidelines (tablet-only) are introduced in ICS.

• Additional API changes for the phone are introduced in Jelly Bean.

12

Theme Incompatibility

• There is not a common cross-platform default theme for developers to derive from.

13

Common UI Pattern Implementations

• Some common UI patterns are not provided as part of the Android framework.

• Pull-to-refresh ListView

• Sliding Drawer Menu (ViewDeck)

14

Common Tools and Usage Patterns

• Some common tools and usage patterns are not provided as part of the Android framework.

• LRU cache that persists to disk

• Image loading with cache support

• Logging and user feedback support

15

Popular Open Source Libraries

16

UI and Compatibility

17

ActionBarSherlock

http://actionbarsherlock.com/

18

Action Bar General Layout

• App icon and “up” affordance

• View switch control

• Action buttons

• Action overflow

19

Split Action Bar

• Main action bar

• Top bar via tabs or spinner

• Bottom bar with action buttons and overflow

20

Contextual Action Bars

21

HoloEverywhere

https://github.com/ChristopheVersieux/HoloEverywhere

• Back ports the Holo themes from Jelly Bean to Eclair and above

22

NineOldAndroids

• Back ports the android.animation.* API from Honeycomb to all previous platforms

• Drawing vs. View properties

http://nineoldandroids.com/

ObjectAnimator.ofFloat(myObject, "translationY", -myObject.getHeight()).start();

23

UnifiedPreference

https://github.com/saik0/UnifiedPreference

24

Android Support Package

• Back ports multi-pane Fragment support from Honeycomb to Donut

25

Android Support Package

• Includes ViewPager, PagerTitleStrip, PagerTabStrip implementations

26

Android Support Package

• Back ports all Notification features from Jelly Bean to Donut

27

Android Support Package

• Back ports asynchronous background Loader support from Honeycomb to Donut

• Includes implementation for a memory-based LruCache

28

Android-MenuDrawer

https://github.com/SimonVT/android-menudrawer

29

Android-PullToRefresh

https://github.com/chrisbanes/Android-PullToRefresh

30

Polaris

https://github.com/cyrilmottier/Polaris

31

Crouton

https://github.com/keyboardsurfer/Crouton

32

Android-Query

http://code.google.com/p/android-query/

• Enables easier UI manipulation via method chaining

AQuery aq = new AQuery(view);        aq.id(R.id.icon) .image(R.drawable.icon) .visible() .clicked(this, "someMethod");aq.id(R.id.name) .text(content.getPname());aq.id(R.id.time) .text(FormatUtility.relativeTime( System.currentTimeMillis(), content.getCreate())) .visible();aq.id(R.id.desc) .text(content.getDesc()) .visible();

33

Caching and Networking

34

DiskLruCache

• Back ports the DiskLruCache from Ice Cream Sandwich to all versions of Android

https://github.com/JakeWharton/DiskLruCache

35

TwoLevelLruCache

• A two-level LRU cache composed of

• first level memory-based LruCache

• second level disk-based DiskLruCache

http://wuman.github.com/TwoLevelLruCache/

36

AndroidImageLoader

• Asynchronous image loading

• Images are downloaded and saved to TwoLevelLruCache via a pool of background threads

• Supports Bitmap transformations

http://wuman.github.com/AndroidImageLoader/

37

HttpResponseCache

• Back ports the persistent HttpResonseCache from Ice Cream Sandwich to all versions of Android

• Provides transparent and automatic persistent caching of HTTP and HTTPS requests that use the HttpUrlConnection class

https://github.com/candrews/HttpResponseCache

38

HTTP-Request

• Provides a simpler and easier interface to HttpURLConnection

• Uses method chaining

https://github.com/kevinsawicki/http-request

HttpRequest.get("http://google.com").receive(System.out);

39

Concurrency and Communication

40

Tape

• Provides a persistent task queue

http://square.github.com/tape/

TaskQueueadd()

peek()remove()

Client UI

Server

ServiceUploadTask UploadTask

41

Otto

• An event bus forked from EventBus of Google Guava targeting the Android platform

http://square.github.com/otto/

Bus

Fragment Fragment

FragmentFragment

Service Activity

Publish Subscribe

42

Data Representation and Processing

43

GSON

• POJO to JSON bi-directional conversion

• Built-in serializers and deserializers for primitive data types

• Supports extensions for complex objects

http://code.google.com/p/google-gson/

44

Jackson JSON Processor

• Streaming JSON parser and serializer

• Supposedly faster than the built-in ones

http://wiki.fasterxml.com/JacksonHome

45

Json-Path

• XPath- and jQuery-like selector for JSON

{ "store": {    "book": [       { "category": "reference",        "author": "Nigel Rees",        "title": "Sayings of the Century",        "price": 8.95      },      { "category": "fianceection",        "author": "Evelyn Waugh",        "title": "Sword of Honour",        "price": 12.99,        "isbn": "0-553-21311-3"      }    ],    "bicycle": {      "color": "red",      "price": 19.95    }  }}

String author = JsonPath.read(json, "$.store.book[1].author");

http://code.google.com/p/json-path/

46

jOOX - Java Object Oriented XML

• XML manipulative parser with selector syntax

• XML document creation

https://github.com/jOOQ/jOOX

47

JSoup

• HTML parser for Java using jQuery-like selector syntax

• Manipulates HTML elements, attributes and text

• Prettifies HTML

http://jsoup.org/

48

OrmLite

• ORM library that persists POJO to SQLite databases

http://ormlite.com/

public class SimpleData {

! @DatabaseField(generatedId = true)! int id;! @DatabaseField(index = true)! String string;! @DatabaseField! long millis;! @DatabaseField! Date date;! @DatabaseField! boolean even;

! SimpleData() {! ! // needed by ormlite! }

! public SimpleData(long millis) {! ! this.date = new Date(millis);! ! this.string = (millis % 1000) + "ms";! ! this.millis = millis;! ! this.even = ((millis % 2) == 0);! }}

49

Google Guava

• Many utilities to make Java development easier

http://code.google.com/p/guava-libraries/

50

Dependency Injection

51

AndroidAnnotations

• Runtime injection of Android views, extras, system services, resources, etc.

• Method annotation to indicate which thread to run in

• Method annotation to bind event listeners to events

http://androidannotations.org/

52

RoboGuice

• Runtime injection of Android views, system services, resources, POJO, etc.

http://code.google.com/p/roboguice/

53

Dagger

• Compile-time dependency injection (binding validation) for Android

• Not as feature-rich as other dependency injection frameworks but much faster

• API very similar to Google Guice

http://square.github.com/dagger/

†54

Testing

55

Android Test Framework

• Built-in Android Test Project support

• Use AndroidTestCase to test non-visual components

• Use Instrumentation to control visual parts of an application

• Command line monkey tool to send random events to device

56

Robotium

• Black-box testing framework for Android

• Improved readability of test cases compared to standard Instrumentation tests

• Handles multiple Android activities

http://code.google.com/p/robotium/

57

Robotium

http://www.vogella.com/articles/AndroidTesting/article.html

// Check that we have the right activitysolo.assertCurrentActivity("wrong activiy", SimpleActivity.class);

// Click a button which will start a new Activity// Here we use the ID of the string to find the right buttonsolo.clickOnButton(solo.getString(R.string.button1));// Validate that the Activity is the correct onesolo.assertCurrentActivity("wrong activiy", SimpleListActivity.class);

// Open the menusolo.sendKey(Solo.MENU);solo.clickOnText("Preferences");solo.clickOnText("User");solo.clearEditText(0);Assert.assertTrue(solo.searchText(""));solo.enterText(0, "http//:www.vogella.com");Assert.assertTrue(solo.searchText("http//:www.vogella.com"));solo.goBack();

58

Mochito

• Android mocking framework

• API makes mocking tests very readable

http://code.google.com/p/mockito/

public void makePurchase(CreditCardManager creditCard) { if (creditCard.getCardType() == CREDIT_CARD_VISA) { creditCard.makePurchase(500); }}

public void testMasterCardTransaction() { CreditCardManager creditCard = Mockito.mock(CreditCardManager.class); Mockito.when(creditCard.getCardType()) .thenReturn(CREDIT_CARD_MASTER);

makePurchase(creditCard);

Mockito.verify(creditCard).getCardType(); Mockito.verifyNoMoreInteractions(creditCard);}

59

Robolectric

• Allows JVM unit testing with the JUnit4 framework

• Reduces testing time from minutes to seconds

• Intercepts Android class loading and forward method bodies to shadow objects

http://pivotal.github.com/robolectric/

60

Robolectric

http://pivotal.github.com/robolectric/

// Test class for MyActivity@RunWith(RobolectricTestRunner.class)public class MyActivityTest { private Activity activity; private Button pressMeButton; private TextView results;

@Before public void setUp() throws Exception { activity = new MyActivity(); activity.onCreate(null); pressMeButton = (Button) activity.findViewById(R.id.press_me_button); results = (TextView) activity.findViewById(R.id.results_text_view); }

@Test public void shouldUpdateResultsWhenButtonIsClicked() throws Exception { pressMeButton.performClick(); String resultsText = results.getText().toString(); assertThat(resultsText, equalTo("Testing Android Rocks!")); }}

61

User Feedback

62

ACRA

• Sends a detailed bug or crash report to Google Docs

http://acra.ch/

63

BugSense/Crittercism

• Collects bug and crash reports

• Generates analytics for crash reports

• Supports fix versioning and notifications

http://www.bugsense.com/docs/android

64

Google Analytics for Android

• Collect user engagement data and generate real time analytics

• Demo

https://developers.google.com/analytics/devguides/collection/android/v2/

65

Bootstrap Project Generator

66

Android Bootstrap

• Includes a full working implementation of

• Android support package

• android-maven-plugin

• RoboGuice

• ActionBarSherlock

• http-request

• GSON

• Robotium

• API on Parse.comhttp://www.androidbootstrap.com/

67

AndroidKickstartR

• Includes a full working implementation of

• Android support package

• android-maven-plugin

• AndroidAnnotations

• ActionBarSherlock

• NineOldAndroids

• ACRA

http://androidkickstartr.com/

68

Tools

69

Android Asset Studio

• Demo

http://android-ui-utils.googlecode.com/hg/asset-studio/dist/index.html

70

Subtle Patterns

• Collection of free tilable textured patterns

• Demo

http://subtlepatterns.com/

71

Charles

• HTTP proxy that enables developers to view all HTTP/HTTPS traffic between the device and the Internet

http://www.charlesproxy.com/

72

Others

73

More Detailed Listing

• App Dev Wiki http://appdevwiki.com/wiki/show/HomePage

• The Ultimate Android Library http://www.theultimateandroidlibrary.com/

• AppBrain Android Developer Tools http://www.appbrain.com/stats/libraries/dev

74

Why open source?

75

Better App Quality

• Normally for various practical reasons we don’t open source the entire app

• Open source useful components within the app into a library

• More debugging for you

• The process of open sourcing forces you to rethink your architecture critically

76

Reciprocity

• A way to give back to the community

• Feels good

77

Portfolio Buildup

• GitHub, not LinkedIn

78

Grow Faster

• The more you engage in the open source community, the faster you learn and grow as a tech professional.

• The process of open sourcing encompasses almost all areas of software development.

79

Better World

• What goes around comes around

• The template for this Keynote presentation is derived from an open source project!

https://github.com/JakeWharton/AndroidDesignKeynoteTheme

80

How to Open Source

81

Disclaimer

What follows is based on the presentation “Effective Open Source” given by Jake Wharton and additionally, a more elaborate presentation based on my own experiences.

https://github.com/JakeWharton/EffectiveOpenSource

82

Component Identification

• Identify the part of your app that can be extracted out as an isolated, reusable component.

• The component should serve to do a focused task very well.

83

Code Abstraction

• Extract the component into a separate package or module and expose only via a small set of public API.

• This is kind of like refactoring. The app should continue to work as expected and the module should be treated just like an external dependency.

• Reiterate the refactoring step several times until

• the exposed public API is minimal and clean

• the client code has good readability

84

Library Project Directory Structure

• Make the module either an independent Java library project or an Android library project depending on whether Android resources are needed in the library.

• Follow a common directory structure as defined in a maven archetype:

• org.apache.maven.archetypes/maven-archetype-quickstart

• de.akquinet.android.archetypes/android-release

85

Android Library Project Directory Structure

library/ Android Library project

test/ Android Test project

samples/ Samples project (Android project)

README Project’s readme

LICENSE Project’s license

NOTICE Notices and attributions required by libraries that the project depends on

86

Java Library Project Directory Structure

library/ Java library project

library/src/main/java/ Java library sources

library/src/test/java/ Test sources

samples/ Samples project (Android project)

README Project’s readme

LICENSE Project’s license

NOTICE Notices and attributions required by libraries that the project depends on

87

Include Tests

• Good libraries are always bundled with tests. It gives people confidence and ensures quality.

• Tests are never enough. Write as many as you can think of.

• Ensure all the tests are passed.

88

Code Quality and Style

• Standardize code conventions.

• Enforce coding style at compile time by using Checkstyle for Java.

• This ensures that future patches have a consistent coding style.

89

Inclusion of Examples

• Add at least one or more working examples.

• Separate examples to showcase a specific aspect of the library.

90

Documentation

• Make sure all exposed public APIs have documentation that follow the javadoc syntax.

• Ensure that a javadoc jar is generated for each release. This is best achieved via the maven-javadoc-plugin.

91

README

• Write a README that follows the Markdown syntax.

• It should include the following sections:

• project description

• how to obtain the library

• snippets of quick start sample code

• external dependencies

• license information

http://daringfireball.net/projects/markdown/syntax

92

Git Ignore

• Always include a .gitignore file to keep the source tree clean. There are many samples online.

• In general exclude these files:

• IDE-specific files (Eclipse.gitignore)

• OS-specific files (OSX.gitignore)

• Android outputs and binaries (Android.gitignore)

• Java compiled classes and package files (Java.gitignore)

https://github.com/github/gitignore

93

Build Management Tool

• Use a build management tool to help people painlessly build your code without needing to know much about the library.

• Most Android people use Maven.

• Write the configuration file that works with your build management tool. In the case of Maven it should be pom.xml.

94

Maven

• Install the latest com.jayway.maven.plugins.android.generation2/android-maven-plugin.

• The packaging for the library project should be either jar or apklib, depending on whether your library is a Java project or an Android Library project.

• The packaging for the samples project should be apk.

http://code.google.com/p/maven-android-plugin/

95

Build with Maven

• Make sure the build management tool builds your project correctly.

• For Maven, you should be able to run the following without errors:

http://maven.apache.org/pom.html

$  mvn  clean  install

96

Continuous Integration

• Setup continuous integration. The simplest open source service is Travis. Have your GitHub repository linked to Travis by activating a hook.

• Write the configuration file .travis.yml.

https://travis-ci.org/

language:  java                                                                                                                                                                                                                                                                                                                        

notifications:    email:  false

before_install:    -­‐  wget  http://dl.google.com/android/android-­‐sdk_r20.0.3-­‐linux.tgz    -­‐  tar  -­‐zxf  android-­‐sdk_r20.0.3-­‐linux.tgz    -­‐  export  ANDROID_HOME=~/builds/username/projectName/android-­‐sdk-­‐linux    -­‐  export  PATH=${PATH}:${ANDROID_HOME}/tools:${ANDROID_HOME}/platform-­‐tools    -­‐  android  list  sdk      -­‐  android  update  sdk  -­‐-­‐filter  1,2,3  -­‐-­‐no-­‐ui  -­‐-­‐force

97

Site Setup

• Setup a project web site.

• If you’re lazy and wish to use just the GitHub README, then the best alternative is the DocumentUp service.

• Configure Travis indicator and Google Analytics tracking for the web site.

http://documentup.com/

<script  src="https://raw.github.com/jeromegn/DocumentUp/master/documentup.min.js"></script><script>

DocumentUp.document({repo:  "wuman/AndroidImageLoader",name:  "AndroidImageLoader",twitter:  ["wuman"],issues:  true,travis:  true,google_analytics:  "UA-­‐4156099-­‐13"

});</script>

98

Issue Management

• GitHub has built-in issue management support, although many developers consider Google Code to be better for issue management.

• Quick triage of issues

99

Mailing List

• Setup a Google Groups mailing list for the project so that people can have a place for discussion.

100

Downloadable Published Packages

• Always make the released packages (usually jars) available for download. Use the com.github.github/downloads-maven-plugin.

• If your library has dependencies, it is best to release a separate jar with dependencies using the maven-assembly-plugin.

https://github.com/github/maven-plugins

101

Release to Sonatype and Maven Central

• Sonatype provides an OSS repository hosting service for free. You can deploy snapshots and releases so that they are also synced periodically to Maven Central.

• Follow their detailed guide.

• In the end you should be able to deploy your project with:

https://docs.sonatype.org/display/Repository/Sonatype+OSS+Maven+Repository+Usage+Guide

$  mvn  clean  package  release:prepare$  mvn  release:perform

102

Promote the Library

• Write a blog post to talk about the motivations behind the project, technical explanations and sample code snippets. Also direct readers to the project page.

• Publish your project everywhere: social networks, related communities, etc.

• Encourage people to use and contribute.

• Ask for feedback.

103

Join the Android Community

• Follow these smart people on Google+:

• Googlers

• Chet Haase, Dan Morrill, Dianne Hackborn, Jean-Baptiste Quéru, Jeff Sharkey, Kirill Grouchnikov, Matias Duarte, Patrick Dubroy, Reto Meier, Roman Nurik, Romain Guy, Tor Norbye, Xavier Ducrohet

• Android Developers

• Community

• Bob Lee, Chris Banes, Cyril Mottier, David Wu (shameless plug), Eric Burke, Jake Wharton, Jesse Wilson, Lars Vogel, Steve Kondik

104

Conclusion

105

106

“Only the children know what they are looking for.”

The Little Prince

106

Thank you

107

Q & A

108