A Deep Dive into Open Source Android Development David Wu @wuman blog.wu-man.com Taipei Google Technology User Group (2013/01/02) Taipei Open Source Software User Group (2012/12/18) ݩஐେላࢿ޻ላܥ ։์ݯᛰԙߦಈऴ୺೭ᚙలߨ࠲ (2012/12/07) 1 

about.me/wuman 2 

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 Honeycomb Gingerbread Froyo Eclair & older Version 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 - 2.3.2 Gingerbread 9 0.2% 2.3.3 - 2.3.7 Gingerbread 10 50.6% 3.1 Honeycomb 12 0.4% 3.2 Honeycomb 13 1.2% 4.0.3 - 4.0.4 Ice Cream Sandwich 15 27.5% 4.1 Jelly Bean 16 5.9% 4.2 Jelly 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/ TaskQueue add() peek() remove() Client UI Server Service UploadTask UploadTask 41 

Otto • An event bus forked from EventBus of Google Guava targeting the Android platform http://square.github.com/otto/ Bus Fragment Fragment Fragment Fragment 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 activity solo.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 button solo.clickOnButton(solo.getString(R.string.button1)); // Validate that the Activity is the correct one solo.assertCurrentActivity("wrong activiy", SimpleListActivity.class); // Open the menu solo.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.com http://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/ DocumentUp.document({ repo:  "wuman/AndroidImageLoader", name:  "AndroidImageLoader", twitter:  ["wuman"], issues:  true, travis:  true, google_analytics:  "UA-­‐4156099-­‐13" }); 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