Successfully modularizing your app

Video: https://www.youtube.com/watch?v=9eikhwWehWk

Modularizing your app seems to be all the hype these days. But why should you actually care? What are the benefits for you and your team? How should a modularized app look like? And how do you start splitting your app?

In this talk, you will learn why modularization matters and how a modularized architecture looks like. We'll study a real-life example project and investigate how modules are set up, organized and configuration is shared across modules. Finally, you'll learn how you can start modularizing your existing app and I'll share what lessons we learned while doing so at Philips Hue.

Articles:
1. why - http://bit.ly/modularization_why
2. architecture - http://bit.ly/modularization_architecture
3. example - http://bit.ly/modularization_example
4. how - http://bit.ly/modularization_how
5. lessons - http://bit.ly/modularization_lessons

Source code: http://bit.ly/modularization_code #androiddev #mobiconf

Transcript

1. @MOLSJEROEN
   SUCCESSFULLY
   MODULARIZING APPS
   

   View Slide

2. @MOLSJEROEN
   @MOLSJEROEN
   @MOLSJEROEN
   

   View Slide

3. @MOLSJEROEN
   WHY
   MODULARIZATION ARCHITECTURE
   HOW TO APPROACH
   LESSONS LEARNED
   

   View Slide

4. WHY
   

   View Slide

5. @MOLSJEROEN
   1. SPEED UP BUILDS
   Gradle does two things to speed up builds
   • Avoid work/caching
   • Parallellization
   Need smaller items of work
   

   View Slide

6. @MOLSJEROEN
   1. SPEED UP BUILDS: SMALLER ITEMS OF WORK
   

   View Slide

7. @MOLSJEROEN
   1. SPEED UP BUILDS: SINGLE MODULE
   

   View Slide

8. @MOLSJEROEN
   1. SPEED UP BUILDS: MULTI MODULE
   

   View Slide

9. @MOLSJEROEN
   1. SPEED UP BUILDS: MULTI MODULE
   

   View Slide

10. @MOLSJEROEN
    2. ALLOW ON DEMAND DELIVERY
    

    View Slide

11. View Slide

12. @MOLSJEROEN
    2. ALLOW ON DEMAND DELIVERY
    At-install delivery
    On demand delivery
    Conditional delivery
    Instant delivery
    Need to split up app
    Support future requirements
    

    View Slide

13. @MOLSJEROEN
    3. SIMPLIFY DEVELOPMENT
    APP
    

    View Slide

14. @MOLSJEROEN
    3. SIMPLIFY DEVELOPMENT
    APP
    FEATURE 1
    FEATURE 2
    FEATURE 3
    FEATURE 4
    FEATURE 5
    FEATURE 6
    

    View Slide

15. IT’S EASIER TO BUILD SEVERAL SMALL
    THINGS THAN TO BUILD ONE BIG THING
    Unknown
    

    View Slide

16. @MOLSJEROEN
    3. SIMPLIFY DEVELOPMENT
    Clear contracts between modules
    • Less spaghetti code
    • Fewer cascading changes
    • Easier in-module refactoring
    Easy to understand code
    Cheaper maintenance
    

    View Slide

17. @MOLSJEROEN
    4. REUSE MODULES
    

    View Slide

18. @MOLSJEROEN
    4. REUSE MODULES: MULTIPLE APPS
    APP 1
    FEATURE 1
    FEATURE 2
    FEATURE 3
    FEATURE 4
    FEATURE 5
    FEATURE 6
    LIBRARY 1 LIBRARY 2
    APP 2
    

    View Slide

19. @MOLSJEROEN
    APP 1
    FEATURE 1
    FEATURE 2
    FEATURE 3
    FEATURE 4
    FEATURE 5
    FEATURE 6
    LIBRARY 1 LIBRARY 2
    APP 2
    4. REUSE MODULES: MULTIPLE APPS
    

    View Slide

20. @MOLSJEROEN
    APP 1
    FEATURE 1
    FEATURE 2
    FEATURE 3
    FEATURE 4
    FEATURE 5
    FEATURE 6
    LIBRARY 1 LIBRARY 2
    APP 2
    FEATURE X
    FEATURE X
    4. REUSE MODULES: MULTIPLE APPS
    

    View Slide

21. @MOLSJEROEN
    APP 1
    FEATURE 1
    FEATURE 2
    FEATURE 3
    FEATURE 4
    FEATURE 5
    FEATURE 6
    LIBRARY 1 LIBRARY 2
    APP 2
    FEATURE X
    FEATURE X
    4. REUSE MODULES: MULTIPLE APPS
    

    View Slide

22. @MOLSJEROEN
    APP 1
    FEATURE 1
    FEATURE 2
    FEATURE 3
    FEATURE 4
    FEATURE 5
    FEATURE 6
    SDK LIBRARY 2
    4. REUSE MODULES: SDK
    

    View Slide

23. @MOLSJEROEN
    APP 1
    FEATURE 1
    FEATURE 2
    FEATURE 3
    FEATURE 4
    FEATURE 5
    FEATURE 6
    SDK LIBRARY 2
    4. REUSE MODULES: SDK
    

    View Slide

24. @MOLSJEROEN
    APP 1
    EXPOSED FEATURE
    WITH INTENT
    FEATURE 2
    FEATURE 3
    FEATURE 4
    FEATURE 5
    FEATURE 6
    LIBRARY 1 LIBRARY 2
    4. REUSE MODULES: EXPOSE FEATURES
    

    View Slide

25. @MOLSJEROEN
    APP 1
    EXPOSED FEATURE
    WITH INTENT
    FEATURE 2
    FEATURE 3
    FEATURE 4
    FEATURE 5
    FEATURE 6
    LIBRARY 1 LIBRARY 2
    4. REUSE MODULES: EXPOSE FEATURES
    

    View Slide

26. @MOLSJEROEN
    APP 1
    FEATURE 1
    FEATURE 2
    FEATURE 3
    FEATURE 4
    FEATURE 5
    FEATURE 6
    AWESOME
    GITHUB LIBRARY LIBRARY 2
    4. REUSE MODULES: OPEN SOURCE
    

    View Slide

27. @MOLSJEROEN
    APP 1
    FEATURE 1
    FEATURE 2
    FEATURE 3
    FEATURE 4
    FEATURE 5
    FEATURE 6
    AWESOME
    GITHUB LIBRARY LIBRARY 2
    4. REUSE MODULES: OPEN SOURCE
    

    View Slide

28. @MOLSJEROEN
    5. EXPERIMENT WITH NEW TECHNOLOGIES
    Rapidly evolving Android landscape
    Need to experiment rapidly
    Cost of wrong technology choice
    Avoid technology lock-in
    

    View Slide

29. @MOLSJEROEN
    Source: https://blog.daftcode.pl/hype-driven-development-3469fc2e9b22
    

    View Slide

30. @MOLSJEROEN
    5. EXPERIMENT WITH NEW TECHNOLOGIES
    APP
    FEATURE 1
    FEATURE 2
    FEATURE 3
    FEATURE 4
    FEATURE 5
    FEATURE 6
    

    View Slide

31. @MOLSJEROEN
    6. SCALING
    Large teams cause new issues
    • Merge conflicts
    • Dependencies
    • Code ownership
    

    View Slide

32. @MOLSJEROEN
    6. SCALING: DEVELOP IN PARALLEL
    Team A Team B
    APP
    FEATURE 1
    FEATURE 2
    FEATURE 3
    FEATURE 4
    FEATURE 5
    FEATURE 6
    

    View Slide

33. @MOLSJEROEN
    6. SCALING: DEVELOP IN PARALLEL
    Team A Team B
    APP
    FEATURE 1
    FEATURE 2
    FEATURE 3
    FEATURE 4
    FEATURE 5
    FEATURE 6
    

    View Slide

34. @MOLSJEROEN
    6. SCALING: OUTSOURCE
    Team A External
    company
    APP
    FEATURE 1
    FEATURE 2
    FEATURE 3
    FEATURE 4
    FEATURE 5
    FEATURE 6
    

    View Slide

35. @MOLSJEROEN
    7. IMPROVE LEGACY CODE
    

    View Slide

36. @MOLSJEROEN
    Aggressive
    High impact
    Lot of work
    Not value focussed
    Risky launch
    Exciting
    Less risky
    Gradual
    Slow
    Tedious
    Continuous releases
    Unsatisfying
    REWRITE REFACTOR
    V S
    

    View Slide

37. @MOLSJEROEN
    Aggressive
    High impact
    Lot of work
    Not value focussed
    Risky launch
    Exciting
    Less risky
    Gradual
    Slow
    Tedious
    Continuous releases
    Unsatisfying
    REWRITE REFACTOR
    V S
    

    View Slide

38. @MOLSJEROEN
    7. IMPROVE LEGACY CODE: REWRITE, REFACTOR OR ACCEPT
    APP
    FEATURE 1
    FEATURE 2
    FEATURE 3
    FEATURE 4
    FEATURE 5
    FEATURE 6
    

    View Slide

39. @MOLSJEROEN
    7. IMPROVE LEGACY CODE: REWRITE, REFACTOR OR ACCEPT
    APP
    FEATURE 1
    FEATURE 2
    FEATURE 3
    FEATURE 4
    FEATURE 5
    FEATURE 6
    

    View Slide

40. @MOLSJEROEN
    7. IMPROVE LEGACY CODE
    Able to rewrite parts of code base
    Keep ability to release
    Gradually roll out possible
    Faster time to market
    

    View Slide

41. @MOLSJEROEN
    8. SIMPLIFY TEST AUTOMATION
    

    View Slide

42. @MOLSJEROEN
    8. SIMPLIFY TEST AUTOMATION
    

    View Slide

43. @MOLSJEROEN
    8. SIMPLIFY TEST AUTOMATION
    Speeds up tests
    Simplified test setup
    Higher test reliability
    

    View Slide

44. @MOLSJEROEN
    WHY: RECAP
    Speed up builds
    Allow on demand delivery
    Simplify development
    Reuse modules across apps
    Experiment with new technologies
    Scale development team
    Improve legacy code
    Simplify test automation
    

    View Slide

45. MODULARIZATION ARCHITECTURE
    

    View Slide

46. YOU HAVE YOUR WAY. I HAVE MY WAY.
    THE RIGHT WAY, THE CORRECT WAY, AND
    THE ONLY WAY DOES NOT EXIST.
    F. Nietzsche
    

    View Slide

47. @MOLSJEROEN
    APP STRUCTURE
    

    View Slide

48. @MOLSJEROEN
    APP STRUCTURE
    

    View Slide

49. @MOLSJEROEN
    APP STRUCTURE
    

    View Slide

50. @MOLSJEROEN
    APP STRUCTURE
    

    View Slide

51. FEATURES ARE A FLOW OF SCREENS
    

    View Slide

52. @MOLSJEROEN
    APP WIREFRAME
    

    View Slide

53. @MOLSJEROEN
    APP WIREFRAME
    

    View Slide

54. @MOLSJEROEN
    APP WIREFRAME
    

    View Slide

55. APPS CONSIST OF SEVERAL FEATURES
    

    View Slide

56. @MOLSJEROEN
    ANDROID APP COMPONENTS
    ACTIVITY SERVICE BROADCAST RECEIVER CONTENT PROVIDER
    

    View Slide

57. @MOLSJEROEN
    ANDROID APP COMPONENTS
    Full screen UI
    Reuse across apps
    Started via explicit or implicit intents
    ACTIVITY SERVICE BROADCAST RECEIVER CONTENT PROVIDER
    

    View Slide

58. @MOLSJEROEN
    IMPLICIT INTENTS
    

    View Slide

59. ANDROID LINKS MULTIPLE APPS
    TOGETHER VIA IMPLICIT INTENTS
    

    View Slide

60. @MOLSJEROEN
    MODULARIZED ARCHITECTURE
    APP
    

    View Slide

61. @MOLSJEROEN
    MODULARIZED ARCHITECTURE
    APP
    FEATURE 1
    FEATURE 2
    FEATURE 3
    FEATURE 4
    FEATURE 5
    FEATURE 6
    

    View Slide

62. @MOLSJEROEN
    MODULARIZED ARCHITECTURE
    APP
    FEATURE 1
    FEATURE 2
    FEATURE 3
    FEATURE 4
    FEATURE 5
    FEATURE 6
    LIBRARY 4 LIBRARY 4
    LIB 1 LIBRARY 2 LIBRARY 3
    

    View Slide

63. @MOLSJEROEN
    FEATURE MODULES
    Full screen, coherent user facing functionality in the app
    Android library module
    Single activity with (optional) navigation graph
    Respond to implicit intents and pass back a result
    Never depend on other features or app
    Depend on several library modules
    APP
    FEATURE 1
    FEATURE 2
    FEATURE 3
    FEATURE 4
    FEATURE 5
    FEATURE 6
    LIBRARY 4 LIBRARY 4
    LIB 1 LIBRARY 2 LIBRARY 3
    

    View Slide

64. @MOLSJEROEN
    LIBRARY MODULES
    Plumbing that is reused across several or all features
    Android library, pure Java or pure Kotlin module
    Never depend on features or app
    Can (but don’t have to) depend on other libraries
    APP
    FEATURE 1
    FEATURE 2
    FEATURE 3
    FEATURE 4
    FEATURE 5
    FEATURE 6
    LIBRARY 4 LIBRARY 4
    LIB 1 LIBRARY 2 LIBRARY 3
    

    View Slide

65. @MOLSJEROEN
    APP MODULE
    Links feature modules together in a useful app
    Android application module
    Depends on other features and libraries
    Orchestrates navigation between features
    Decides what features are enabled using feature toggles
    Doesn’t contain much code
    APP
    FEATURE 1
    FEATURE 2
    FEATURE 3
    FEATURE 4
    FEATURE 5
    FEATURE 6
    LIBRARY 4 LIBRARY 4
    LIB 1 LIBRARY 2 LIBRARY 3
    

    View Slide

66. @MOLSJEROEN
    ADVANTAGES
    Application structure
    Navigation
    Testing
    Scaling
    Feature flagging
    Experiment with new technology
    

    View Slide

67. @MOLSJEROEN
    APPLICATION STRUCTURE
    

    View Slide

68. @MOLSJEROEN
    DASHBOARD FEATURE
    

    View Slide

69. @MOLSJEROEN
    DASHBOARD ACTIVITY
    

    View Slide

70. @MOLSJEROEN
    LOGIN FEATURE
    

    View Slide

71. @MOLSJEROEN
    SHARING FEATURE
    

    View Slide

72. @MOLSJEROEN
    NAVIGATION
    Split navigation in smaller parts
    • Within a feature -> handled by the feature
    • Between features -> handled by the app module
    APP
    FEATURE 1
    FEATURE 2
    FEATURE 3
    FEATURE 4
    FEATURE 5
    FEATURE 6
    

    View Slide

73. @MOLSJEROEN
    NAVIGATION: IN FEATURE
    Android Navigation components
    • Visualize navigation flow
    • Find back screens
    • Easy code browsing
    

    View Slide

74. @MOLSJEROEN
    NAVIGATION: IN FEATURE
    

    View Slide

75. @MOLSJEROEN
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/nav_host_fragment"
    android:name="androidx.navigation.fragment.NavHostFragment"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:defaultNavHost="true"
    app:navGraph="@navigation/login_graph"/>
    NAVIGATION: IN FEATURE
    

    View Slide

76. @MOLSJEROEN
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/nav_host_fragment"
    android:name="androidx.navigation.fragment.NavHostFragment"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:defaultNavHost="true"
    app:navGraph="@navigation/login_graph"/>
    NAVIGATION: IN FEATURE
    

    View Slide

77. @MOLSJEROEN
    android:id="@+id/login_graph"
    app:startDestination="@id/welcomeFragment">
    android:id="@+id/welcomeFragment"
    android:name="modularization.features.login.WelcomeFragment" />
    android:id="@+id/loginFragment"
    android:name="modularization.features.login.LoginFragment" />
    android:id="@+id/avatarFragment"
    android:name="modularization.features.login.AvatarFragment"/>
    
    NAVIGATION: IN FEATURE
    

    View Slide

78. @MOLSJEROEN
    android:id="@+id/login_graph"
    app:startDestination="@id/welcomeFragment">
    android:id="@+id/welcomeFragment"
    android:name="modularization.features.login.WelcomeFragment" />
    android:id="@+id/loginFragment"
    android:name="modularization.features.login.LoginFragment" />
    android:id="@+id/avatarFragment"
    android:name="modularization.features.login.AvatarFragment"/>
    
    NAVIGATION: IN FEATURE
    

    View Slide

79. @MOLSJEROEN
    android:id="@+id/login_graph"
    app:startDestination="@id/welcomeFragment">
    android:id="@+id/welcomeFragment"
    android:name="modularization.features.login.WelcomeFragment" />
    android:id="@+id/loginFragment"
    android:name="modularization.features.login.LoginFragment" />
    android:id="@+id/avatarFragment"
    android:name="modularization.features.login.AvatarFragment"/>
    
    NAVIGATION: IN FEATURE
    

    View Slide

80. @MOLSJEROEN
    //...
    android:id="@+id/welcomeFragment"
    android:name="modularization.features.login.WelcomeFragment" >
    android:id="@+id/action_welcomeFragment_to_loginFragment"
    app:destination="@id/loginFragment" />
    
    
    
    
    NAVIGATION: IN FEATURE
    

    View Slide

81. @MOLSJEROEN
    //...
    android:id="@+id/welcomeFragment"
    android:name="modularization.features.login.WelcomeFragment" >
    android:id="@+id/action_welcomeFragment_to_loginFragment"
    app:destination="@id/loginFragment" />
    
    
    
    
    NAVIGATION: IN FEATURE
    

    View Slide

82. @MOLSJEROEN
    findNavController().navigate(R.id.action_welcomeFragment_to_loginFragment)
    NAVIGATION: IN FEATURE
    

    View Slide

83. @MOLSJEROEN
    NAVIGATION: IN FEATURE
    

    View Slide

84. @MOLSJEROEN
    NAVIGATION: BETWEEN FEATURES
    startActivity(Intent(activity, DashboardActivity::class.java))
    

    View Slide

85. @MOLSJEROEN
    NAVIGATION: BETWEEN FEATURES
    startActivity(Intent("action.dashboard.open"))
    

    View Slide

86. @MOLSJEROEN
    NAVIGATION: BETWEEN FEATURES
    xmlns:android="http://schemas.android.com/apk/res/android"
    package="modularization.dashboard">
    
    
    
    
    
    
    
    
    
    

    View Slide

87. @MOLSJEROEN
    NAVIGATION: BETWEEN FEATURES
    xmlns:android="http://schemas.android.com/apk/res/android"
    package="modularization.dashboard">
    
    
    
    
    
    
    
    
    
    

    View Slide

88. @MOLSJEROEN
    NAVIGATION: BETWEEN FEATURES
    String duplication of action
    In depth knowledge of intent creation
    Other apps could also handle action
    

    View Slide

89. @MOLSJEROEN
    NAVIGATION: BETWEEN FEATURES
    APP
    FEATURE 1
    FEATURE 2
    FEATURE 3
    FEATURE 4
    FEATURE 5
    FEATURE 6
    ACTIONS LIBRARY 4
    LIB 1 LIBRARY 2 LIBRARY 3
    

    View Slide

90. @MOLSJEROEN
    NAVIGATION: BETWEEN FEATURES
    object Actions {
    fun openLoginIntent() = Intent("action.login.open")
    fun openDashboardIntent() = Intent("action.dashboard.open")
    fun openSharingIntent() = Intent("action.sharing.open")
    }
    activity.startActivity(Actions.openDashboardIntent())
    

    View Slide

91. @MOLSJEROEN
    NAVIGATION: BETWEEN FEATURES
    object Actions {
    fun openLoginIntent() = Intent("action.login.open")
    fun openDashboardIntent() = Intent("action.dashboard.open")
    fun openSharingIntent() = Intent("action.sharing.open")
    }
    activity.startActivity(Actions.openDashboardIntent())
    

    View Slide

92. @MOLSJEROEN
    NAVIGATION: BETWEEN FEATURES
    object Actions {
    fun openDashboardIntent(userId: String) =
    Intent(context, "action.dashboard.open")
    .putExtra(EXTRA_USER, UserArgs(userId))
    }
    activity.startActivity(Actions.openDashboardIntent("userId"))
    

    View Slide

93. @MOLSJEROEN
    NAVIGATION: BETWEEN FEATURES
    object Actions {
    fun openDashboardIntent(userId: String) =
    Intent(context, "action.dashboard.open")
    .putExtra(EXTRA_USER, UserArgs(userId))
    }
    activity.startActivity(Actions.openDashboardIntent("userId"))
    

    View Slide

94. @MOLSJEROEN
    NAVIGATION: BETWEEN FEATURES
    

    View Slide

95. @MOLSJEROEN
    NAVIGATION: BETWEEN FEATURES
    object Actions {
    fun openLoginIntent(context: Context) =
    internalIntent(context, "action.login.open")
    private fun internalIntent(context: Context, action: String) =
    Intent(action).setPackage(context.packageName)
    }
    

    View Slide

96. @MOLSJEROEN
    NAVIGATION: BETWEEN FEATURES
    object Actions {
    fun openLoginIntent(context: Context) =
    internalIntent(context, "action.login.open")
    private fun internalIntent(context: Context, action: String) =
    Intent(action).setPackage(context.packageName)
    }
    

    View Slide

97. @MOLSJEROEN
    NAVIGATION: BETWEEN FEATURES
    Implicit intents
    Actions module
    Abstract away feature parameters
    Restrict to current package
    

    View Slide

98. @MOLSJEROEN
    TESTING
    UNIT
    INTEGRATION
    E2E
    

    View Slide

99. @MOLSJEROEN
    TESTING
    APP
    FEATURE 1
    FEATURE 2
    FEATURE 3
    FEATURE 4
    FEATURE 5
    FEATURE 6
    LIBRARY 4 LIBRARY 4
    LIB 1 LIBRARY 2 LIBRARY 3
    

    View Slide

100. @MOLSJEROEN
     FEATURE TESTING
     class LoginFlowTest {
     @Rule
     @JvmField
     var mActivityTestRule = ActivityTestRule(LoginActivity::class.java)
     @Test
     fun loginFlowTest() {
     onView(withId(R.id.button_login_start)).perform(click())
     onView(withId(R.id.button_login_signin)).perform(click())
     onView(withId(R.id.button_login_toapp)).check(matches(isDisplayed()))
     }
     }
     

     View Slide

101. @MOLSJEROEN
     FEATURE TESTING
     class LoginFlowTest {
     @Rule
     @JvmField
     var mActivityTestRule = ActivityTestRule(LoginActivity::class.java)
     @Test
     fun loginFlowTest() {
     onView(withId(R.id.button_login_start)).perform(click())
     onView(withId(R.id.button_login_signin)).perform(click())
     onView(withId(R.id.button_login_toapp)).check(matches(isDisplayed()))
     }
     }
     

     View Slide

102. @MOLSJEROEN
     FEATURE TESTING
     class LoginFlowTest {
     @Rule
     @JvmField
     var mActivityTestRule = ActivityTestRule(LoginActivity::class.java)
     @Test
     fun loginFlowTest() {
     onView(withId(R.id.button_login_start)).perform(click())
     onView(withId(R.id.button_login_signin)).perform(click())
     onView(withId(R.id.button_login_toapp)).check(matches(isDisplayed()))
     }
     }
     

     View Slide

103. @MOLSJEROEN
     APP FLOW TESTING
     class AppFlowTest {
     @Rule
     @JvmField
     var mActivityTestRule = ActivityTestRule(MainActivity::class.java)
     @Test
     fun test_criticalUserFlow_throughoutEntireApp() {
     onView(withId(modularization.login.R.id.button_login_start)).perform(click())
     onView(withId(modularization.login.R.id.button_login_signin)).perform(click())
     onView(withId(modularization.login.R.id.button_login_toapp)).perform(click())
     onView(withId(R.id.action_albums)).perform(click())
     onView(withId(R.id.action_sharing)).perform(click())
     onView(withId(R.id.button_social_facebook)).perform(click())
     onView(withId(R.id.recyclerView_sharing_contacts)).check(matches(isDisplayed()))
     }
     }
     

     View Slide

104. @MOLSJEROEN
     SCALING: TEAMS
     Team A Team B
     APP
     FEATURE 1
     FEATURE 2
     FEATURE 3
     FEATURE 4
     FEATURE 5
     FEATURE 6
     LIBRARY 4 LIBRARY 4
     LIB 1 LIBRARY 2 LIBRARY 3
     

     View Slide

105. @MOLSJEROEN
     APP 1
     FEATURE 1
     FEATURE 2
     FEATURE 3
     FEATURE 4
     FEATURE 5
     FEATURE 6
     LIBRARY 1 LIBRARY 2
     APP 2
     FEATURE X
     FEATURE X
     SCALING: APPS
     

     View Slide

106. @MOLSJEROEN
     SCALING: SDKS
     APP
     EXPOSED FEATURE
     WITH INTENT
     FEATURE 2
     FEATURE 3
     FEATURE 4
     FEATURE 5
     FEATURE 6
     LIBRARY 4 AWESOME GITHUB LIBRARY
     LIB 1 SDK LIBRARY 3
     

     View Slide

107. @MOLSJEROEN
     SCALING: TECHNOLOGY
     APP
     FEATURE 1
     FEATURE 2
     FEATURE 3
     FEATURE 4
     FEATURE 5
     FEATURE 6
     LIBRARY 4 LIBRARY 4
     LIB 1 LIBRARY 2 LIBRARY 3
     

     View Slide

108. @MOLSJEROEN
     IMPROVE LEGACY
     APP
     FEATURE 1
     FEATURE 2
     FEATURE 3
     FEATURE 4
     FEATURE 5
     FEATURE 6
     LIBRARY 4 LIBRARY 4
     LIB 1 LIBRARY 2 LIBRARY 3
     

     View Slide

109. @MOLSJEROEN
     IMPROVE LEGACY: REWRITE FEATURE
     APP
     FEATURE 1
     FEATURE 2
     FEATURE 3
     FEATURE 4
     FEATURE 5
     FEATURE 6
     LIBRARY 4 LIBRARY 4
     LIB 1 LIBRARY 2 LIBRARY 3
     

     View Slide

110. @MOLSJEROEN
     IMPROVE LEGACY: REWRITE FEATURE
     APP
     FEATURE 1
     FEATURE 2
     FEATURE 3
     FEATURE 4
     FEATURE 5
     FEATURE 6
     LIBRARY 4 LIBRARY 4
     LIB 1 LIBRARY 2 LIBRARY 3
     FEATURE 5*
     

     View Slide

111. @MOLSJEROEN
     IMPROVE LEGACY: FEATURE FLAGS
     object Actions {
     fun openLoginIntent() =
     if (FeatureFlag.loginRewrite) { Intent("action.login2.open") }
     else { Intent("action.login.open") }
     }
     

     View Slide

112. @MOLSJEROEN
     IMPROVE LEGACY: FEATURE FLAGS
     object Actions {
     fun openLoginIntent() =
     if (FeatureFlag.loginRewrite) { Intent("action.login2.open") }
     else { Intent("action.login.open") }
     }
     

     View Slide

113. @MOLSJEROEN
     IMPROVE LEGACY: ROLL OUT
     

     View Slide

114. @MOLSJEROEN
     

     View Slide

115. @MOLSJEROEN
     ARCHITECTURE: RECAP
     Easy code navigation
     Simple in-feature and across feature navigation
     Better test automation
     Enables scaling
     Able to experiment with new technologies
     Staged rollout of rewritten features
     

     View Slide

116. HOW TO APPROACH
     

     View Slide

117. @MOLSJEROEN
     APP
     FEATURE
     FEATURE
     FEATURE
     FUTURE.
     FEATURE
     FUTURE
     FEATURE
     FUTURE
     FEATURE
     OLD APP
     LIB LIBRARY FUTURE LIBRARY
     APP
     FEATURE
     FEATURE
     FEATURE
     FUTURE FEATURE
     FUTURE FEATURE
     FUTURE FEATURE
     LIB 1
     LIB FUTURE LIBRARY
     LIBRARY
     CHOOSE YOUR SIDE
     

     View Slide

118. @MOLSJEROEN
     PULL CODE UP
     APP
     FEATURE
     FEATURE
     FEATURE
     FUTURE FEATURE
     FUTURE FEATURE
     FUTURE FEATURE
     OLD APP
     LIB LIBRARY FUTURE LIBRARY
     Pull modules up
     

     View Slide

119. @MOLSJEROEN
     PULL CODE UP
     Conceptually very simple
     Extract features without dependency issues
     Huge upfront change
     Encourages gradual modularization
     Incompatible with Butterknife: change to R2.id.***
     Features need to be extracted before libraries
     

     View Slide

120. @MOLSJEROEN
     PUSH CODE DOWN
     APP
     FEATURE
     FEATURE
     FEATURE
     FUTURE FEATURE
     FUTURE FEATURE
     FUTURE FEATURE
     LIB 1
     LIB FUTURE LIBRARY
     LIBRARY
     Push modules down
     

     View Slide

121. @MOLSJEROEN
     PUSH CODE DOWN
     Initially a lot harder
     Extract libraries without dependency issues
     No big upfront change
     Forces aggressive modularisation
     Better grip on modularisation process
     Bottom up code clean up
     

     View Slide

122. @MOLSJEROEN
     APP
     FEATURE
     FEATURE
     FEATURE
     FUTURE.
     FEATURE
     FUTURE
     FEATURE
     FUTURE
     FEATURE
     OLD APP
     LIB LIBRARY FUTURE LIBRARY
     APP
     FEATURE
     FEATURE
     FEATURE
     FUTURE FEATURE
     FUTURE FEATURE
     FUTURE FEATURE
     LIB 1
     LIB FUTURE LIBRARY
     LIBRARY
     CHOOSE YOUR SIDE
     

     View Slide

123. @MOLSJEROEN
     APP
     FEATURE
     FEATURE
     FEATURE
     FUTURE.
     FEATURE
     FUTURE
     FEATURE
     FUTURE
     FEATURE
     OLD APP
     LIB LIBRARY FUTURE LIBRARY
     APP
     FEATURE
     FEATURE
     FEATURE
     FUTURE FEATURE
     FUTURE FEATURE
     FUTURE FEATURE
     LIB 1
     LIB FUTURE LIBRARY
     LIBRARY
     CHOOSE YOUR SIDE
     

     View Slide

124. @MOLSJEROEN
     CONSIDERATIONS
     Make a big initial push
     Aggressively restrict visibility
     Combine with general code improvements
     Postpone/avoid problems
     • Cut dependencies using abstractions
     • Deprecate and rewrite
     • Clean up internals later
     

     View Slide

125. WHEN PLANNING IS LONG THEN IT’S
     WRONG, IF IT’S TIGHT THEN IT’S RIGHT
     Elon musk
     

     View Slide

126. LESSONS LEARNED
     

     View Slide

127. @MOLSJEROEN
     CONFIGURE MODULES
     Adding a new module must be easy
     Maintaining module configurations must be easy
     

     View Slide

128. @MOLSJEROEN
     CONFIGURE MODULES
     subprojects {
     afterEvaluate { project ->
     if (project.hasProperty('android')) {
     android {
     buildToolsVersion Config.buildTools
     compileSdkVersion Config.compileSdk
     defaultConfig {
     minSdkVersion Config.minSdk
     targetSdkVersion Config.targetSdk
     }
     compileOptions {
     sourceCompatibility Config.javaVersion
     targetCompatibility Config.javaVersion
     } } } } }
     

     View Slide

129. @MOLSJEROEN
     CONFIGURE MODULES
     subprojects {
     afterEvaluate { project ->
     if (project.hasProperty('android')) {
     android {
     buildToolsVersion Config.buildTools
     compileSdkVersion Config.compileSdk
     defaultConfig {
     minSdkVersion Config.minSdk
     targetSdkVersion Config.targetSdk
     }
     compileOptions {
     sourceCompatibility Config.javaVersion
     targetCompatibility Config.javaVersion
     } } } } }
     

     View Slide

130. @MOLSJEROEN
     CONFIGURE MODULES
     subprojects {
     afterEvaluate { project ->
     if (project.hasProperty('android')) {
     android {
     buildToolsVersion Config.buildTools
     compileSdkVersion Config.compileSdk
     defaultConfig {
     minSdkVersion Config.minSdk
     targetSdkVersion Config.targetSdk
     }
     compileOptions {
     sourceCompatibility Config.javaVersion
     targetCompatibility Config.javaVersion
     } } } } }
     

     View Slide

131. @MOLSJEROEN
     CONFIGURE MODULES
     apply plugin: 'com.android.library'
     apply plugin: 'kotlin-android-extensions'
     apply plugin: 'kotlin-android'
     dependencies {
     implementation project(':libraries:ui-components')
     implementation project(':libraries:actions')
     implementation Deps.androidx_material
     implementation Deps.androidx_constraintlayout
     implementation Deps.androidx_navigation_fragment
     implementation Deps.androidx_navigation_ui
     testImplementation Deps.testlib_junit
     androidTestImplementation Deps.testandroidx_runner
     androidTestImplementation Deps.testandroidx_rules
     androidTestImplementation Deps.testandroidx_espressocore
     }
     

     View Slide

132. @MOLSJEROEN
     CONFIGURE MODULES
     

     View Slide

133. @MOLSJEROEN
     MODULE GRAPH
     apply from: 'https://raw.githubusercontent.com/JakeWharton/SdkSearch/master/
     gradle/projectDependencyGraph.gradle'
     ./gradlew projectDependencyGraph
     

     View Slide

134. @MOLSJEROEN
     MODULE GRAPH
     

     View Slide

135. @MOLSJEROEN
     ORGANIZE SETTINGS.GRADLE
     include ':app', ':features:login', ':features:dashboard', ':features:sharing', ':libraries:ui-
     components', ':libraries:actions'
     

     View Slide

136. @MOLSJEROEN
     ORGANIZE SETTINGS.GRADLE
     include ':app'
     include ':features:login'
     include ':features:dashboard'
     include ':features:sharing'
     include ':libraries:ui-components'
     include ':libraries:actions'
     

     View Slide

137. @MOLSJEROEN
     ORGANIZE SETTINGS.GRADLE
     include ':app'
     include ':features:login'
     include ':features:dashboard'
     include ':features:sharing'
     include ':libraries:ui-components'
     include ':libraries:actions'
     

     View Slide

138. @MOLSJEROEN
     MODULE INTERNALS
     

     View Slide

139. @MOLSJEROEN
     MODULE INTERNALS - ORGANIZATION
     

     View Slide

140. @MOLSJEROEN
     MODULE INTERNALS - ORGANIZATION
     

     View Slide

141. @MOLSJEROEN
     MODULE INTERNALS - PACKAGE NAME
     features: [project-name].features.[feature-name]

     e.g. modularization.features.login
     libraries: [project-name].libraries.[library-name]

     e.g. modularization.libraries.actions
     

     View Slide

142. @MOLSJEROEN
     MODULE INTERNALS - PACKAGE NAME
     import android.content.Intent
     import android.os.Bundle
     import androidx.appcompat.app.AppCompatActivity
     import modularization.features.login.LoginActivity
     import modularization.features.sharing.SharingActivity
     import modularization.features.dashboard.DashboardActivity
     import modularization.libraries.actions.Actions
     import modularization.libraries.uicomponents.RoundedButton
     

     View Slide

143. @MOLSJEROEN
     LAYOUT PREVIEWS
     

     View Slide

144. @MOLSJEROEN
     LAYOUT PREVIEWS
     

     View Slide

145. @MOLSJEROEN
     LAYOUT PREVIEWS
     xmlns:android="http://schemas.android.com/apk/res/android"
     package="modularization.features.dashboard">
     
     
     
     
     

     View Slide

146. @MOLSJEROEN
     LAYOUT PREVIEWS
     xmlns:android="http://schemas.android.com/apk/res/android"
     package="modularization.features.dashboard">
     
     
     
     
     

     View Slide

147. @MOLSJEROEN
     LAYOUT PREVIEWS
     

     View Slide

148. @MOLSJEROEN
     DEPENDENCY MANAGEMENT
     object Config {
     val minSdk = 23
     val javaVersion = JavaVersion.VERSION_1_8
     val buildTools = "28.0.3"
     }
     object Versions {
     val androidx_core = "1.0.1"
     val androidx_nav = "2.0.0"
     ...
     }
     object Deps {
     val androidx_core = "androidx.core:core-ktx:${Versions.androidx_core}"
     val androidx_nav_fragment = "androidx.navigation:navigation-fragment-ktx:${Versions.androidx_nav}"
     val androidx_nav_ui = “androidx.navigation:navigation-ui-ktx:${Versions.androidx_nav}"
     ...
     }
     

     View Slide

149. @MOLSJEROEN
     CONFIGURE MODULES
     apply plugin: 'com.android.library'
     apply plugin: 'kotlin-android-extensions'
     apply plugin: 'kotlin-android'
     dependencies {
     implementation project(':libraries:ui-components')
     implementation project(':libraries:actions')
     implementation Deps.androidx_material
     implementation Deps.androidx_constraintlayout
     implementation Deps.androidx_navigation_fragment
     implementation Deps.androidx_navigation_ui
     testImplementation Deps.testlib_junit
     androidTestImplementation Deps.testandroidx_runner
     androidTestImplementation Deps.testandroidx_rules
     androidTestImplementation Deps.testandroidx_espressocore
     }
     

     View Slide

150. @MOLSJEROEN
     DEPENDENCY MANAGEMENT
     ./gradlew dependencyUpdates
     

     View Slide

151. @MOLSJEROEN
     SPEED UP BUILDS
     dependencies {
     // Avoid doing this
     api project(':libraries:ui-components')
     // Do this instead
     implementation project(':libraries:ui-components')
     }
     

     View Slide

152. @MOLSJEROEN
     API VS IMPLEMENTATION DEPENDENCY
     APP
     

     View Slide

153. @MOLSJEROEN
     API DEPENDENCY
     APP
     

     View Slide

154. @MOLSJEROEN
     API DEPENDENCY
     APP
     

     View Slide

155. @MOLSJEROEN
     API DEPENDENCY
     APP
     

     View Slide

156. @MOLSJEROEN
     IMPLEMENTATION DEPENDENCY
     APP
     

     View Slide

157. WRAP UP
     

     View Slide

158. THERE ARE NO BIG PROBLEMS, THERE
     ARE JUST A LOT OF LITTLE PROBLEMS.
     Henry Ford
     

     View Slide

159. @MOLSJEROEN
     MODULARIZATION HAS TONS OF BENEFITS
     APP FEATURES LIBRARIES
     NAVIGATION WITHIN AND BETWEEN FEATURES
     PUSH CODE DOWN
     SIMPLIFY ADDING MODULES
     

     View Slide

160. @MOLSJEROEN
     

     View Slide

161. @MOLSJEROEN
     HTTPS://JEROENMOLS.COM/BLOG
     

     View Slide

162. @MOLSJEROEN
     REFERENCES
     Blog posts:
     1. http://bit.ly/modularization_why
     2. http://bit.ly/modularization_architecture
     3. http://bit.ly/modularization_example
     4. http://bit.ly/modularization_how
     5. http://bit.ly/modularization_lessons
     http://bit.ly/modularization_code
     

     View Slide

163. @MOLSJEROEN
     IMAGE CREDITS
     Welcome image by Clement127
     https://flic.kr/p/n9ctTn
     Official Android documentation
     https://d.android.com
     Font awesome
     https://fontawesome.com/
     

     View Slide

164. MOLSJEROEN
     

     View Slide