Android App Architecture & Navigation

Transcript

1. Android App Architecture & Navigation Bryan Herbst (@bryancherbst)

2. Activities & Fragments

3. STOP

4. STOP If you like what you have, keep it

5. When to use what?

6. Where we’ve been

7. In the beginning there was Activity

8. Activity Entry point to your application

9. Activity Entry point to your application Has a Window

10. Activity Entry point to your application Has a Window Has

    a lifecycle

11. Activity Entry point to your application Has a Window Has

    a lifecycle Responds to configuration changes

12. Activity Entry point to your application Has a Window Has

    a lifecycle Responds to configuration changes ActivityManager handles back stack

13. Activity Layout inflation View manipulation Click handlers Animations Navigation Menu

    creation Menu item callbacks Database calls Networking calls Disk I/O Sensor input Geolocation

14. Activity Window transitions can be difficult !

15. Activity Window transitions can be difficult A lot of plumbing

    !

16. Activity Window transitions can be difficult A lot of plumbing

    Nuanced (and limited) backstack !

17. Enter Honeycomb (3.0)

18. None

19. Fragments!

20. Fragment Has lifecycle (less than Activity)

21. Fragment Has lifecycle (less than Activity) Backstack via FragmentManager

22. Fragment Has lifecycle (less than Activity) Backstack via FragmentManager Composable

23. Fragment Has lifecycle (less than Activity) Backstack via FragmentManager Composable

    Belong to an Activity

24. Fragments Transactions are annoying !

25. Fragments Transactions are annoying Lifecycles are annoying !

26. Fragments Transactions are annoying Lifecycles are annoying Can still be

    too big !

27. Fragments Transactions are annoying Lifecycles are annoying Can still be

    too big Bugs !

28. Fragments Transactions are annoying Lifecycles are annoying Can still be

    too big Bugs Differences from Activity !

29. Meanwhile

30. View-based architecture

31. View Draws things Reacts to user interaction

32. View Almost no lifecycle No backstack !

33. Where are we now?

34. Single activity app Easier to manage transitions

35. Single activity app Easier to manage transitions Composable UI elements

36. Single activity app Easier to manage transitions Composable UI elements

    Google can be opinionated

37. Don’t like lifecyles? Use Lifecycle

38. class MainActivity : Activity { override fun onStart() { super.onStart()

    analytics.reportStart() } }

39. activity.lifecycle .addObserver(AnalyticsObserver()) class AnalyticsObserver : LifecycleObserver { @OnLifecycleEvent(ON_START) fun trackPageLoad()

    { analytics.reportStart() } }

40. activity.lifecycle .addObserver(AnalyticsObserver()) class AnalyticsObserver : LifecycleObserver { @OnLifecycleEvent(ON_START) fun trackPageLoad()

    { analytics.reportStart() } }

41. Fragment refresher

42. Which Fragments? Framework fragments Support fragments

43. Which Fragments? Framework fragments Support fragments ! "

44. Fragment transactions

45. Fragment transactions fragmentManager.beginTransaction()

46. Fragment transactions fragmentManager.beginTransaction() .add()

47. Fragment transactions fragmentManager.beginTransaction() .remove()

48. Fragment transactions fragmentManager.beginTransaction() .replace()

49. Fragment transactions fragmentManager.beginTransaction() .show()

50. Fragment transactions fragmentManager.beginTransaction() .hide()

51. Fragment transactions fragmentManager.beginTransaction() .addToBackstack()

52. Fragment transactions fragmentManager.beginTransaction() .commit()

53. Fragment transactions fragmentManager.beginTransaction() .add() .replace() .hide() .addToBackstack() .commit()

54. Transactions are asynchronous

55. The IllegalStateException com.awesomeapp E/MainActivity: java.lang.IllegalStateException: Cannot perform this action after

    onSaveInstanceState

56. The IllegalStateException FM State

57. The IllegalStateException FM State add()

58. The IllegalStateException FM State add()

59. The IllegalStateException FM State add() hide()

60. The IllegalStateException FM State add() hide() onStop()!!

61. The IllegalStateException FM State add() hide() onStop()!! Persisted add() hide()

62. The IllegalStateException FM State onStart() Persisted add() hide()

63. The IllegalStateException FM State add() hide() Persisted add() hide() replace()

64. The IllegalStateException After onSaveInstanceState any future changes may be lost

65. Okay, but async transactions suck

66. Commit() commit() executePendingTransactions() commitAllowingStateLoss() commitNow() commitNowAllowingStateLoss()

67. Commit() commit() executePendingTransactions() commitAllowingStateLoss() commitNow() commitNowAllowingStateLoss()

68. Commit() commit() executePendingTransactions() commitAllowingStateLoss() commitNow() commitNowAllowingStateLoss()

69. Commit() commit() executePendingTransactions() commitAllowingStateLoss() commitNow() commitNowAllowingStateLoss()

70. Back stack addToBackStack(null)

71. Back stack popBackStack()

72. Back stack addToBackStack("screenA")

73. Back stack addToBackStack("screenA")

74. Back stack addToBackStack("screenB")

75. Back stack addToBackStack("screenC")

76. Back stack popBackStack("screenA", 0)

77. But that’s a lot of work

78. Navigation

79. Navigation Challenges Transitions

80. Navigation Challenges Transitions Back stack management

81. Navigation Challenges Transitions Back stack management Up vs. back

82. Navigation Challenges Transitions Back stack management Up vs. back Passing

    data

83. Navigation Challenges Transitions Back stack management Up vs. back Passing

    data Deep linking

84. Android Jetpack: Navigation

85. Principles Navigation is a stack

86. Principles Navigation is a stack Up never exits the app

87. Principles Navigation is a stack Up never exits the app

    Up = Back within your app

88. Principles Navigation is a stack Up never exits the app

    Up = Back within your app Deep linking should yield the same stack

89. Navigation (the library)

90. Navigation library No more Fragment transactions!

91. Navigation library No more Fragment transactions! No more startActivity()!

92. Navigation library No more Fragment transactions! No more startActivity()! Just

    call navigate()

93. Navigation Graph All the destinations in your app, plus the

    action that connect them.

94. Navigation Graph New XML resource type!

95. Navigation tooling

96. Navigator What destination types are available?

97. NavHost Where do those destinations reside?

98. NavController How do I get there?

99. Current Navigators ActivityNavigator

100. Current Navigators ActivityNavigator FragmentNavigator

101. <fragment android:id="@+id/navHost" android:name= "androidx.navigation.fragment.NavHostFragment" android:layout_width="match_parent" android:layout_height="match_parent" app:defaultNavHost="true" app:navGraph="@navigation/nav_graph" />

102. <fragment android:id="@+id/navHost" android:name= "androidx.navigation.fragment.NavHostFragment" android:layout_width="match_parent" android:layout_height="match_parent" app:defaultNavHost="true" app:navGraph="@navigation/nav_graph" />

103. Do the navigation Navigation .findNavController(view) .navigate(R.id.action_id)

104. Destinations: Deep link Destinations can have deep links <fragment android:id="@+id/home”

     android:name="com.example.HomeFragment" android:label="fragment_home"> <deepLink app:uri="http://example.com/detail"/> </fragment>

105. Actions: Animations Actions can have transition animations <action android:id="@+id/action_home_to_detail" app:destination="@id/detail"

     app:popEnterAnim="@anim/slide_in_left" app:popExitAnim="@anim/slide_out_right" app:enterAnim="@anim/slide_in_right" app:exitAnim="@anim/slide_out_left"/>

106. Actions: back stack Each action can define its own behavior

     <action android:id="@+id/home_to_details" app:destination="@id/details” app:popUpTo="@id/splash” app:popUpToInclusive="false" />

107. Arguments Actions can all have arguments <fragment> <argument android:name="name" android:defaultValue="Joe"

     /> </fragment>

108. Arguments Works with deep links! <fragment> <argument android:name="name" android:defaultValue="Joe" />

     <deepLink app:uri="example.com/{name}" /> </fragment>

109. Safeargs androidx.navigation.safeargs

110. Safeargs androidx.navigation.safeargs Generates argument wrapper classes

111. Safeargs Demo time!

112. Demo time!

113. Custom destination You can make your own Navigator!

114. What’s missing Some integration with common elements like bottom navigation

115. What’s missing Some integration with common elements like bottom navigation

     Shared element transitions

116. What’s missing Some integration with common elements like bottom navigation

     Shared element transitions Nested navigation graphs

117. What’s missing Some integration with common elements like bottom navigation

     Shared element transitions Nested navigation graphs Result data (e.g. startActivityForResult())

118. What if I want to migrate to Navigation?

119. I currently have…

120. Single Activity

121. Single Activity Set up navigation graph

122. Single Activity Set up navigation graph Each Fragment is a

     destination

123. Single Activity Set up navigation graph Each Fragment is a

     destination Every transaction is an action

124. Single Activity Set up navigation graph Each Fragment is a

     destination Every transaction is an action Define arguments

125. Single Activity Set up navigation graph Each Fragment is a

     destination Every transaction is an action Define arguments Replace transactions with NavController.navigate()

126. Multiple activities Start by making a graph for each Activity

127. Multiple activities Start by making a graph for each Activity

     If you want a single Activity, combine Activities one screen at a time

128. Activity Chrome

129. Activity Chrome CoordinatorLayout .setStatusBarBackgroundColor()

130. Activity Features <activity android:name=".MainActivity" android:windowSoftInputMode="adjustPan" />

131. Activity Features <activity android:name=".MainActivity" android:windowSoftInputMode="adjustPan" /> activity.window .setSoftInputMode(SOFT_INPUT_ADJUST_PAN)

132. More complex Watch for updates! Provide feedback!

133. Resources https://developer.android.com /topic /libraries /architecture /navigation