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)

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about.me/wuman2

Overview

• Why use open source?

• Popular open source Android libraries

• Why open source?

• How to open source

• Conclusion

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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

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Not Possible Otherwise

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

• Platform compatibility

• UI compatibility

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Android app development is

NOT easy!

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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%

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UI Requirements for Featured Apps

• Follow Android Design guidelines

• Navigation

• Action Bar

• Use common UI patterns and icons

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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.

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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

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Popular Open Source Libraries

16

UI and Compatibility

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ActionBarSherlock

http://actionbarsherlock.com/

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Action Bar General Layout

• App icon and “up” affordance

• View switch control

• Action buttons

• Action overflow

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Split Action Bar

• Main action bar

• Top bar via tabs or spinner

• Bottom bar with action buttons and overflow

20

Contextual Action Bars

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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

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Android Support Package

• Includes ViewPager, PagerTitleStrip, PagerTabStrip implementations

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Android Support Package

• Back ports all Notification features from Jelly Bean to Donut

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Android Support Package

• Back ports asynchronous background Loader support from Honeycomb to Donut

• Includes implementation for a memory-based LruCache

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Android-MenuDrawer

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

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Android-PullToRefresh

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

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Polaris

https://github.com/cyrilmottier/Polaris

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Crouton

https://github.com/keyboardsurfer/Crouton

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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();

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Caching and Networking

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DiskLruCache

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

https://github.com/JakeWharton/DiskLruCache

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TwoLevelLruCache

• A two-level LRU cache composed of

• first level memory-based LruCache

• second level disk-based DiskLruCache

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

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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/

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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

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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);

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Concurrency and Communication

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Tape

• Provides a persistent task queue

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

TaskQueueadd()

peek()remove()

Client UI

Server

ServiceUploadTask UploadTask

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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/

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Jackson JSON Processor

• Streaming JSON parser and serializer

• Supposedly faster than the built-in ones

http://wiki.fasterxml.com/JacksonHome

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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/

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jOOX - Java Object Oriented XML

• XML manipulative parser with selector syntax

• XML document creation

https://github.com/jOOQ/jOOX

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JSoup

• HTML parser for Java using jQuery-like selector syntax

• Manipulates HTML elements, attributes and text

• Prettifies HTML

http://jsoup.org/

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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);! }}

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Google Guava

• Many utilities to make Java development easier

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

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Dependency Injection

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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/

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RoboGuice

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

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

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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

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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

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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/

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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();

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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);}

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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/

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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!")); }}

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User Feedback

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ACRA

• Sends a detailed bug or crash report to Google Docs

http://acra.ch/

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BugSense/Crittercism

• Collects bug and crash reports

• Generates analytics for crash reports

• Supports fix versioning and notifications

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

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Google Analytics for Android

• Collect user engagement data and generate real time analytics

• Demo

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

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Bootstrap Project Generator

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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/

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AndroidKickstartR

• Includes a full working implementation of

• Android support package

• android-maven-plugin

• AndroidAnnotations

• ActionBarSherlock

• NineOldAndroids

• ACRA

http://androidkickstartr.com/

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Tools

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Android Asset Studio

• Demo

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

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Subtle Patterns

• Collection of free tilable textured patterns

• Demo

http://subtlepatterns.com/

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Charles

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

http://www.charlesproxy.com/

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Others

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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

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Why open source?

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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

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Reciprocity

• A way to give back to the community

• Feels good

77

Portfolio Buildup

• GitHub, not LinkedIn

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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.

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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

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How to Open Source

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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

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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.

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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

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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

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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

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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

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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.

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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.

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Inclusion of Examples

• Add at least one or more working examples.

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

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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.

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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

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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

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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.

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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/

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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

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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

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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>

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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

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Mailing List

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

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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

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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

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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.

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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

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Conclusion

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

The Little Prince

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Thank you

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Q & A

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