Clean Android Client Architecture with Rx and MVVM (GDG Kaohsiung #27)

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Transcript

2. CLEAN ANDROID CLIENT ARCHITECTURE WITH RX AND MVVM GDG KAOHSIUNG #27
3. ABOUT ME SHIAMI WU
4. 6 YEARS EXPERIENCE MOBILE APP DEVELOPER.
5. ANDROID DEV, IOS DEV, PRODUCT DEV, UX DESIGN, SERVICE DESIGN, STARTUP, GDG KAOHSIUNG, APP TALK, AND ETC.
6. TODAY WE WILL TALK ABOUT.. ▸ Review the Issues and Challenges in Android Client App Development ▸ Uncle Bob: Clean Architecture ▸ Everything is a Stream - ReactiveX to the Rescue! ▸ The Most Powerful REST Client Library - Retrofit ▸ Android MVVM Pattern - Data Binding Support Library ▸ The Combined Solution - Demo and Recap
7. TODAY WE WILL TALK ABOUT.. ▸ Review the Issues and Challenges in Android Client App Development ▸ Uncle Bob: Clean Architecture ▸ Everything is a Stream - ReactiveX to the Rescue! ▸ The Most Powerful REST Client Library - Retrofit ▸ Android MVVM Pattern - Data Binding Support Library ▸ The Combined Solution - Demo and Recap
8. WHAT IS AN ACTIVITY OR A FRAGMENT? ▸ Screens (UI) ▸ Flows ▸ Fundamental building blocks of Android app ▸ Lifecycle
9. ACTIVITY LIFECYCLE
10. ACTIVITY LIFECYCLE STATUS ▸ On app startup ▸ On app resume ▸ On focus gain ▸ On focus loss ▸ On app swap or device sleep ▸ Orientation changed ▸ Being killed
11. ACTIVITY LIFECYCLE HANDLING ▸ onCreate(), onStart(), onResume() ▸ onPause(), onStop(), onDestroy() ▸ onSaveInstanceState() ▸ Handle activity restart ▸ Handle resource usage ▸ Handle your model status ▸ Handle sync and async tasks
12. FRAGMENT LIFECYCLE
14. ADVOCATING AGAINST ANDROID FRAGMENTS The Corner, Square Engineering Blog HTTPS://CORNER.SQUAREUP.COM/2014/10/ADVOCATING-AGAINST-ANDROID-FRAGMENTS.HTML
15. WHAT YOUR PARENTS NEVER TOLD YOU ABOUT FRAGMENTS ▸ Lifecycle is too complex ▸ We have to rely solely on default constructors, rather than custom constructors ▸ Nested Fragments are prone to bugs and limitations. ▸ Hard to trace, hard to debug ▸ View controllers? Not easy to decouple views and models ▸ Fragment transactions is async - Unstable state ▸ Fragment recreation problem - Missing outer class
16. ANOTHER PROBLEM HERE.. ▸ How to communicate activities and fragments? ▸ Intent? ▸ onActivityResult()? ▸ Handler? ▸ Broadcast? ▸ Interface?
17. HOW TO COMMUNICATE ACTIVITIES AND FRAGMENTS? ▸ Not easy to communicate ▸ close coupled ▸ boilerplate code ▸ Solution: Event bus ▸ But not easy to manage the event listeners if too many
18. ADVOCATING AGAINST ANDROID FRAGMENTS ▸ Avoid using fragments ▸ “One Activity, Multiple Views” approach ▸ An Investigation into Flow and Mortar
19. TEXT REAL WORLD ISSUES ABOUT ACTIVITY & FRAGMENT ▸ They are UI screens, flow controls, and lifecycles ▸ Put everything in them (Nightmare!) ▸ The code is hard to trace and debug ▸ Strong connection to each other ▸ Hard to do unit test ▸ Mess up with the lifecycle ▸ Especially the next thing we are going to talk about..
20. ANDROID LIFECYCLE IS NOT EASY TO DEAL WITH The truth is..
21. ANDROID CLIENT APP NOW LET’S TALK ABOUT
22. WHAT IS AN ANDROID CLIENT APP? ▸ Will connect to a backend server on the internet ▸ Network async tasks ▸ REST API calls
23. ANDROID LIFECYCLE IS NOT EASY TO DEAL WITH Recap:
24. ESPECIALLY WHEN DOING ASYNC TASKS
25. WHY?
26. Android Lifecycle and Async Tasks In Parallel Universes!
28. NETWORK ASYNC TASKS WITH ANDROID FRAMEWORK?
29. TEXT DO NETWORK ASYNC TASKS WITH ANDROID FRAMEWORK ▸ Thread, Handler ▸ AsyncTask ▸ IntentService, ResultReceiver ▸ Loader, AsyncTaskLoader
30. THREAD ▸ Plain old Java Thread ▸ No cancellation policy ▸ Hard way to deliver results in UI thread ▸ Nested codes with Handler, Runnable, Looper
31. https://speakerdeck.com/jdamcd/async-android
32. ASYNCTASK ▸ Easier usage than Thread ▸ Callbacks for UI and background operations ▸ Callback hell ▸ Not bound to activity or fragment lifecycle ▸ Hard to handle errors
33. https://speakerdeck.com/jdamcd/async-android
34. https://speakerdeck.com/jdamcd/async-android
35. …OTHER COMPONENTS? ▸ Volley? ▸ There are also some restrictions and problems ▸ Hard to manage for many REST API calls in the real world
36. ANDROID ASYNC TASK REAL WORLD CHALLENGES REVIEW AND DISCUSSION
37. ANDROID ASYNC TASK REAL WORLD CHALLENGES ▸ Persistence across configuration changes (Context leak) ▸ Strong relationship (Close coupling) ▸ Callback hell ▸ Lack of error handling ▸ Boilerplate codes ▸ Messy, hard-to-trace, maybe-buggy, dirty architecture
38. ANDROID CLIENT APP DEVELOPMENT RECAP: WE HAVE TWO MAJOR PROBLEMS COMBINED TOGETHER ▸ Android lifecycle is too complex, especially with async tasks ▸ Android async tasks are hard to write and manage when firing many RESTful requests
39. TODAY WE WILL TALK ABOUT.. ▸ Review the Issues and Challenges in Android Client App Development ▸ Uncle Bob: Clean Architecture ▸ Everything is a Stream - ReactiveX to the Rescue! ▸ The Most Powerful REST Client Library - Retrofit ▸ Android MVVM Pattern - Data Binding Support Library ▸ The Combined Solution - Demo and Recap
40. UNCLE BOB WHO IS
41. ROBERT CECIL MARTIN (KNOWN AS UNCLE BOB) ▸ An American software engineering, author, public speaker ▸ Publications ▸ (2002). Agile software development: principles, patterns, and practices. ▸ (2009). Clean code: a handbook of agile software craftsmanship. ▸ (2011). The clean coder: a code of conduct for professional programmers.
42. HTTP://BLOG.8THLIGHT.COM/UNCLE-BOB/2012/08/13/THE-CLEAN-ARCHITECTURE.HTML THE CLEAN ARCHITECTURE (AUG, 2012)
43. THE CLEAN ARCHITECTURE ▸ The architecture produce a system ▸ Independent of Frameworks ▸ Testable ▸ Independent of UI ▸ Independent of Database ▸ Independent of any external agency ▸ Independency of each level (Decoupled, Replaceable)
44. “ARCHITECTURE IS ABOUT INTENT, NOT FRAMEWORKS” Uncle Bob
45. CLEAN ANDROID ARCHITECTURE HOW ABOUT THE
46. HTTP://FERNANDOCEJAS.COM/2014/09/03/ARCHITECTING-ANDROID-THE-CLEAN-WAY/ ARCHITECTING ANDROID…THE CLEAN WAY?
47. HTTP://FERNANDOCEJAS.COM/2014/09/03/ARCHITECTING-ANDROID-THE-CLEAN-WAY/ KEEPING THE BUSINESS RULES NOT KNOWING ANYTHING AT ALL ABOUT THE OUTSIDE WORLD
48. HTTP://FERNANDOCEJAS.COM/2014/09/03/ARCHITECTING-ANDROID-THE-CLEAN-WAY/ PRESENTATION LAYER: LOGICS RELATED WITH VIEWS (MVC, MVP, MVVM)
49. HTTP://FERNANDOCEJAS.COM/2014/09/03/ARCHITECTING-ANDROID-THE-CLEAN-WAY/ DOMAIN LAYER: BUSINESS LOGICS (PURE JAVA MODULES)
50. HTTP://FERNANDOCEJAS.COM/2014/09/03/ARCHITECTING-ANDROID-THE-CLEAN-WAY/ DATA LAYER: REPOSITORY PATTERN (REPLACEABLE)
51. SHOW ME THE CODE! https://github.com/android10/Android-CleanArchitecture
52. CLEAN ANDROID ARCHITECTURE ▸ Easy to maintain codes ▸ Easy to test ▸ Easy to manage relations ▸ Decoupled
53. THE CLEAN ANDROID ARCHITECTURE IS GREAT! BUT.. Real world challenges
54. THE ASYNC TASK ISSUES STILL BOTHER ME! Real world challenges
55. HTTP://FERNANDOCEJAS.COM/2015/07/18/ARCHITECTING-ANDROID-THE-EVOLUTION/ ARCHITECTING ANDROID…THE EVOLUTION
56. HTTP://FERNANDOCEJAS.COM/2015/07/18/ARCHITECTING-ANDROID-THE-EVOLUTION/ DOMAIN LAYER: CONSIDER NETWORK INTERACTORS (ASYNC TASKS)
57. ANY BETTER APPROACH?
60. CLEAN ANDROID CLIENT ARCHITECTURE WITH RX AND MVVM
61. TODAY WE WILL TALK ABOUT.. ▸ Review the Issues and Challenges in Android Client App Development ▸ Uncle Bob: Clean Architecture ▸ Everything is a Stream - ReactiveX to the Rescue! ▸ The Most Powerful REST Client Library - Retrofit ▸ Android MVVM Pattern - Data Binding Support Library ▸ The Combined Solution - Demo and Recap
65. TEXT WHAT ARE REACTIVE EXTENSIONS (REACTIVEX, RX) ? ▸ Rx, initiated by Erik Meijer (C# and .Net, then adapted to many different languages), is a library that allows you to apply FRP to any language.
67. REACTIVEX IS A COMBINATION OF DIFFERENT CONCEPTS. ReactiveX TEXT
68. IT’S REALLY NOT EASY TO GET INTO IT, BUT.. LET’S SPLIT IT UP FIRST! ReactiveX TEXT
69. REACTIVEX KEYWORDS: ▸ Observer Pattern ▸ Functional programming ▸ Reactive programming ▸ FRP (Functional Reactive Programming)
70. REACTIVEX KEYWORDS: ▸ Observer Pattern ▸ Functional programming ▸ Reactive programming ▸ FRP (Functional Reactive Programming)
71. OBSERVER PATTERN ▸ Pub/Sub (Publisher/Subscriber) Pattern ▸ Publisher ▸ Subscriber ▸ Observer Pattern ▸ Observable ▸ Observer
72. HTTPS://WWW.DOTBLOGS.COM.TW/JOYSDW12/2013/03/13/96531 OBSERVER PATTERN
73. REACTIVEX KEYWORDS: ▸ Observer Pattern ▸ Functional programming ▸ Reactive programming ▸ FRP (Functional Reactive Programming)
74. IT’S ALMOST CERTAINLY TRUE THAT FUNCTIONAL PROGRAMMING IS THE NEXT BIG THING. Uncle Bob HTTPS://PRAGPROG.COM/MAGAZINES/2013-01/FUNCTIONAL-PROGRAMMING-BASICS
75. WHY?
76. FUNCTIONAL PROGRAMMING ▸ Definition on Wikipedia ▸ In computer science, functional programming is a programming paradigm—a style of building the structure and elements of computer programs—that treats computation as the evaluation of mathematical functions and avoids changing-state and mutable data.
77. FUNCTIONAL PROGRAMMING ▸ Definition on Wikipedia ▸ In computer science, functional programming is a programming paradigm—a style of building the structure and elements of computer programs—that treats computation as the evaluation of mathematical functions and avoids changing-state and mutable data.
78. FUNCTIONAL PROGRAMMING ▸ Output o = sqrt(Input); ▸ sqrt() is a black box ▸ Modularity ▸ Easy to maintain ▸ Better software architecture
79. FUNCTIONAL PROGRAMMING ▸ Output o2 = abs(cos(sqrt(Input))); ▸ Separate a big problem into several boxes ▸ Easy to test ▸ Focus on data flow
80. ASYNC ▸ Multi-threading programming is hard ▸ Hard to program ▸ Hard to test ▸ Mutable shared state ▸ Complex logic
81. FUNCTIONAL PROGRAMMING ▸ Definition on Wikipedia ▸ In computer science, functional programming is a programming paradigm—a style of building the structure and elements of computer programs—that treats computation as the evaluation of mathematical functions and avoids changing-state and mutable data ▸ Much easier for multithreading programming
82. FUNCTIONAL PROGRAMMING ▸ Features ▸ First-class functions (Concept) ▸ Function as first-class citizen ▸ Allow functions as arguments and results of other functions
83. FUNCTIONAL PROGRAMMING ▸ Features ▸ Higher-order functions (Techniques) ▸ Map ▸ Filter ▸ Reduce ▸ And more..
84. FUNCTIONAL PROGRAMMING ▸ Features ▸ First-class functions ▸ Immutable variables ▸ Function composition ▸ No side-effect ▸ Etc.
85. TEXT FUNCTIONAL PROGRAMMING EXAMPLE ▸ We have a number list. ▸ 1, 2, 3, 5, 7, 9, 11, 12, 13 ▸ Multiply 2, and get the largest number less than 10
86. MULTIPLY 2, AND GET THE LARGEST NUMBER LESS THAN 10 TEXT FUNCTIONAL PROGRAMMING EXAMPLE (NORMAL WAY)
87. MULTIPLY 2, AND GET THE LARGEST NUMBER LESS THAN 10 FUNCTIONAL PROGRAMMING EXAMPLE (RX WAY)
88. HTTP://WWW.ORACLE.COM/WEBFOLDER/TECHNETWORK/TUTORIALS/OBE/JAVA/LAMBDA-QUICKSTART/INDEX.HTML#OVERVIEW FUNCTIONAL PROGRAMMING EXAMPLE (LAMBDA EXPRESSION)
89. REACTIVEX KEYWORDS: ▸ Observer Pattern ▸ Functional programming ▸ Reactive programming ▸ FRP (Functional Reactive Programming)
90. REACTIVE PROGRAMMING ▸ Wikipedia ▸ In computing, reactive programming is a programming paradigm oriented around data flows and the propagation of change ▸ There are certain datatypes that represent a value "over time"
91. REACTIVE PROGRAMMING ▸ b = 10, c = 2; ▸ a = b + c; ▸ b = 5; ▸ > print a ▸ // 12
92. REACTIVE PROGRAMMING ▸ b = 10, c = 2; ▸ a = b + c; ▸ b = 5; ▸ > print a ▸ // 7
93. HTTP://CCTG.BLOGSPOT.TW/2015/08/REACTIVE-PROGRAMMING.HTML REACTIVE PROGRAMMING ▸ Excel or Spreadsheet
94. REACTIVE PROGRAMMING ▸ Data stream on GUI ▸ A mouse movement event (Position data stream) ▸ 20:01:35:000 at (200, 200) ▸ 20:01:35:001 at (201, 200) ▸ 20:01:35:002 at (202, 200) ▸ 20:01:35:003 at (203, 200) ▸ 20:01:35:004 at (204, 200) ▸ …
95. REACTIVE PROGRAMMING ▸ Data stream on GUI ▸ Reactive to mouse move ▸ To receive current position ▸ Become a mouse movement event ▸ Reactive to mouse movement event ▸ To change corresponding UI ▸ For example: ▸ Display hint at certain position ▸ Open a menu at certain position
96. REACTIVE PROGRAMMING ▸ Wikipedia ▸ In computing, reactive programming is a programming paradigm oriented around data flows and the propagation of change ▸ There are certain datatypes that represent a value "over time"
97. REACTIVEX KEYWORDS: ▸ Observer Pattern ▸ Functional programming ▸ Reactive programming ▸ FRP (Functional Reactive Programming)
98. FRP (FUNCTIONAL REACTIVE PROGRAMMING) ▸ Definition on Wikipedia ▸ Functional reactive programming (FRP) is a programming paradigm for reactive programming (asynchronous dataflow programming) using the building blocks of functional programming (e.g. map, reduce, filter). ▸ FRP has been used for programming graphical user interfaces (GUIs), robotics, and music, aiming to simplify these problems by explicitly modeling time.
99. RECAP: WE HAVE TWO MAJOR PROBLEMS COMBINED TOGETHER ▸ Android lifecycle is too complex, especially with async tasks ▸ Android async tasks are hard to write and manage when firing many RESTful requests
102. INTRODUCTION TO RX HTTP://REACTIVEX.IO/TUTORIALS.HTML
103. RX ON ANDROID
107. LET’S LEARN BY CODING. RxJava
108. TEXT SOME TIPS BEFORE START.. ▸ Anonymous class
109. TEXT SOME TIPS BEFORE START.. ▸ Anonymous class ▸ Enable you to declare and instantiate a class at the same time ▸ Use them if you need to use a local class only once
110. THE PROBLEM IS.. Anonymous Class TEXT
113. TEXT SOME TIPS BEFORE START.. ▸ Lambda expression ▸ One issue with anonymous classes is that if the implementation of your anonymous class is very simple, such as an interface that contains only one method, then the syntax of anonymous classes may seem unwieldy and unclear ▸ Lambda expressions enable you to do this, to treat functionality as method argument, or code as data
114. Before After
115. LAMBDA EXPRESSION ON ANDROID ▸ Lambda expression ▸ Java 8 ▸ Android ▸ Java 6, 7 ▸ Retrolambda ▸ Android Studio ▸ Support lambda expression for “shorten display only”
116. RXJAVA BASICS ▸ Characters ▸ Observable, Subscriber(Observer) ▸ Action ▸ To subscribe
117. HTTPS://WWW.DOTBLOGS.COM.TW/JOYSDW12/2013/03/13/96531 RECAP: OBSERVER PATTERN
118. RXJAVA BASICS
119. HTTP://REACTIVEX.IO/DOCUMENTATION/OPERATORS.HTML#CREATING CREATING OBSERVABLES
120. CREATING OBSERVABLES ▸ Observable.just() ▸ Observable.from() ▸ Observable.create()
121. CREATING OBSERVABLES ▸ Observable.just() ▸ Convert an object or a set of objects into an Observable that emits that or those objects
122. CREATING OBSERVABLES ▸ Observable.from() ▸ Convert some other object or data structure into an Observable
123. CREATING OBSERVABLES ▸ Observable.create() ▸ Create an Observable from scratch by calling observer methods programmatically
124. CREATING SUBSCRIBER // onNext()
125. RXJAVA BASICS Separated Combined
126. RXANDROID ▸ AndroidScheduler ▸ Thread control ▸ .observeOn() ▸ .subscribeOn()
127. RXLIFECYCLE ▸ Helper to handle Android lifecycle ▸ This helper automatically determines (based on the lifecycle sequence itself) when the source should stop emitting items ▸ The easy way ▸ extends Rx-Activity or Rx-Fragment family ▸ Observable.bindToLifecycle()
128. TEXT RECAP: REACTIVEX ON ANDROID ▸ RxJava ▸ Release the power of ReactiveX and FRP on Android ▸ RxAndroid ▸ Android Thread controller for RxJava ▸ RxLifecycle ▸ RxJava Helper for complex Activity and Fragment lifecycle
130. Observable
131. Subscriber
132. To subscribe
133. AndroidScheduler (RxAndroid)
134. bindToLifecycle (RxLifecycle)
138. HTTP://REACTIVEX.IO/DOCUMENTATION/OPERATORS.HTML RX OPERATORS
139. ▸ Multiply 2, and get the largest number less than 10
140. HTTP://REACTIVEX.IO/DOCUMENTATION/OBSERVABLE.HTML RX DIAGRAM
141. TEXT RX ALTERNATIVE ▸ Java 9 Flow API
142. RX IS MORE POWERFUL THAN THAT. TRY IT! https://www.facebook.com/groups/rxandroid/
143. TODAY WE WILL TALK ABOUT.. ▸ Review the Issues and Challenges in Android Client App Development ▸ Uncle Bob: Clean Architecture ▸ Everything is a Stream - ReactiveX to the Rescue! ▸ The Most Powerful REST Client Library - Retrofit ▸ Android MVVM Pattern - Data Binding Support Library ▸ The Combined Solution - Demo and Recap
145. HTTP://SQUARE.GITHUB.IO/RETROFIT/ RETROFIT FEATURES ▸ Most powerful Android Client library ▸ Don’t need to write a lot of boilerplate codes ▸ Easy and flexible to use ▸ Allow to plugin your modified HTTP client, JSON converter, and etc. ▸ Only need to define the API interface to work
146. THE MOST IMPORTANT THING IS.. Retrofit TEXT
147. RETROFIT SUPPORTS RXJAVA
148. EXAMPLE: GET THE REPO LIST OF AN ORG ON GITHUB RETROFIT SUPPORTS RXJAVA ▸ It help you to trigger the RESTful requests and create the Observables
149. RETROFIT SUPPORTS RXJAVA ▸ Just use the Observable created by Retrofit and subscribe the Subscriber to work!
150. RETROFIT SUPPORTS RXJAVA
151. RETROFIT 2.0.0 ▸ Still beta (2.0.0-beta3), but okay to use with RxJava Observable ▸ Rewritten, so not compatible with 1.x ▸ Directly use and deeply integrate with OkHttp
152. TODAY WE WILL TALK ABOUT.. ▸ Review the Issues and Challenges in Android Client App Development ▸ Uncle Bob: Clean Architecture ▸ Everything is a Stream - ReactiveX to the Rescue! ▸ The Most Powerful REST Client Library - Retrofit ▸ Android MVVM Pattern - Data Binding Support Library ▸ The Combined Solution - Demo and Recap
153. HTTP://TECH.VG.NO/2015/07/17/ANDROID-DATABINDING-GOODBYE-PRESENTER-HELLO-VIEWMODEL/ WHY MVVM?
154. HTTP://TECH.VG.NO/2015/07/17/ANDROID-DATABINDING-GOODBYE-PRESENTER-HELLO-VIEWMODEL/ WHY MVVM?
155. http://developer.android.com/intl/zh-tw/tools/data-binding/guide.html
156. TEXT DATA BINDING FEATURES ▸ Data Binding Library automatically generate those boilerplate codes ▸ project/app/build/intermediates/classes/debug/ com.example.application/databinding/ MainActivityBinding.java ▸ Two-way binding with Observable objects ▸ Easy to test with ViewModel ▸ Mock test data in ViewModel
157. TEXT DATA BINDING FEATURES ▸ Expression language ▸ android:visibility="@{age < 13 ? View.GONE : View.VISIBLE}” ▸ Advanced binding ▸ Support RecyclerView
158. TEXT DATA BINDING ▸ The real power of data binding can be used by giving your data objects the ability to notify when data changes ▸ Observable data objects
159. TEXT TWO-WAY BINDING WITH OBSERVABLE OBJECTS
160. OBSERVABLE DATA OBJECTS
161. OBSERVABLE DATA OBJECTS ▸ Observable objects ▸ extends BaseObservable ▸ Observable fields ▸ ObservableField<String> ▸ ObservableInt, ObservableLong, … ▸ Observable collections ▸ ObservableArrayMap, ObservableArrayList
162. TEXT ANDROID MVVM DATA BINDING EXAMPLE ▸ ANDROID DATABINDING: GOODBYE PRESENTER, HELLO VIEWMODEL! ▸ https://github.com/Nilzor/mvp-to-mvvm-transition
163. MVP APPROACH? ▸ Android MVP, Retrofit & RX ▸ https://github.com/appfoundry/android-mosby-rx
164. TODAY WE WILL TALK ABOUT.. ▸ Review the Issues and Challenges in Android Client App Development ▸ Uncle Bob: Clean Architecture ▸ Everything is a Stream - ReactiveX to the Rescue! ▸ The Most Powerful REST Client Library - Retrofit ▸ Android MVVM Pattern - Data Binding Support Library ▸ The Combined Solution - Demo and Recap
165. ANDROID CLIENT APP DEVELOPMENT RECAP: WE HAVE TWO MAJOR PROBLEMS COMBINED TOGETHER ▸ Android lifecycle is too complex, especially with async tasks ▸ Android async tasks are hard to write and manage when firing many RESTful requests
166. https://medium.com/@manuelvicnt/rxjava-android-mvvm-app-structure-with-retrofit-a5605fa32c00#.pkbvfn1p6 Register and login flow with Retrofit and Data Binding Library
167. DEMO CODES. RxJava, RxAndroid, RxLifecycle, Retrofit, Data Binding Library HTTPS://GITHUB.COM/GDGKOAHSIUNG/GDGKAOHSIUNG27
168. ANY QUESTION? THANK YOU! Contact: jiamingwu15@gmail.com