MVVM & Nested Fragment: Views - ViewModel Contracts

As smartphones get more and more powerful and with bigger screens, the complexity of tasks that people want to be able to do with them follow the same growth. Google has become very opinionated about how to do architecture and best practices, but examples are often overly simplified and not very dynamic.

Fragments are making a comeback, combined with LiveData and ViewModels. As we adopt these architecture components into our apps, how can we build support for complex use cases with multiple fragments on screen? Should each fragment have a ViewModel? What about custom views?

ViewModel Contracts propose the idea of having fragments (and potentially custom views) declare a ViewModel & LiveData via interface to abstract out all of the communication details between nested fragments and their parents. In this talk, we explain in detail how to implement them, how architecture components deal with ViewModels, ViewModelFactories and how we can reuse them.

Transcript

1. MV V M & N E S T E D F R AG M E N T/ V I E W S - V I E W M O D E L CO N T R AC TS M A R C O S DA M A S C E N O S R . A N D R O I D E NG I N E E R @marcospaulosd B R E T E R I C K S O N A N D R O I D E NG I N E E R I NG M A N AG E R linkedin.com/in/breterickson/
4. A N D R O I D H O N E YCO M B R E L E A S E D O N F E B , 2 01 1
5. A N D R O I D H O N E YCO M B R E L E A S E D O N F E B , 2 01 1 C O M P L E X A N D DY N A M I C V I E W S B EC A M E MO R E PO P U L A R
6. A N D R O I D H O N E YCO M B R E L E A S E D O N F E B , 2 01 1 C O M P L E X A N D DY N A M I C V I E W S B EC A M E MO R E PO P U L A R H E L LO F R AG M E N TS
7. A N D R O I D U I CO M P L E X I T Y TA B L E TS A R E N OW H E R E TO B E S E E N B U T P H O N E S A R E B I G
8. A N D R O I D U I CO M P L E X I T Y TA B L E TS A R E N OW H E R E TO B E S E E N B U T P H O N E S A R E B I G A P P S A R E B EC O M I NG C O N S TA N T LY C O M P L E X
9. A N D R O I D U I CO M P L E X I T Y TA B L E TS A R E N OW H E R E TO B E S E E N B U T P H O N E S A R E B I G A P P S A R E B EC O M I NG C O N S TA N T LY C O M P L E X
10. H O W D O W E CO M M U N IC AT E B E T W E E N S O M A N Y D I F F E R E N T V I E W S A N D F R AG M E N T S
11. CO M M U N I C AT I O N B E T W E E N F R AG M E N T S I N T E N T B R OA D C A S T/ B U N D L E S
12. CO M M U N I C AT I O N B E T W E E N F R AG M E N T S C A L L B AC K S & I N T E R FAC E S O NC L IC K L I ST E N E R I M P L BY AC T IV I T Y - C A L L BAC K H E L L C A ST AC T IV I T Y I N TO A N I N T E R FAC E I N S I D E T H E F R AG M E N T - W H AT I F I WA N T TO R E U S E I T 
 I N S I D E A NOT H E R F R AG M E N T V I E W CO N T R O L L E R S J U G G L E CO M M U N I C AT IO N LOG IC
13. CO M M U N I C AT I O N B E T W E E N F R AG M E N T S R X S U B J EC TS I N J EC T I N G A N R X S U B J EC T I N TO A F R AG M E N T ’ S V M / P R E S E N T E R M AY E X PO S E M U TA B L E VA L U E S E V E RY W H E R E R X S U B J EC T S A R E N OT FAU LT TO L E R A N T - AT T H E E N D, A FA NC Y A LT E R N AT IV E TO E V E N T B U S - O N E E R R O R E M I T T E D 
 A N D YO U ’ R E D O N E D I F F IC U LT TO D E B U G & U N D E R S TA N D F LOW A S CO M P L E X I T Y I NC R E A S E S
14. P O P U L A R A R C H I T EC T U R E S
15. P O P U L A R A R C H I T EC T U R E S D O M A I N - DATA
16. P O P U L A R A R C H I T EC T U R E S D O M A I N - DATA DATA L AY E R R E P O S I TO RY DATA S TO R E A P I C L I E N T
17. P O P U L A R A R C H I T EC T U R E S D O M A I N - DATA DATA L AY E R R E P O S I TO RY DATA S TO R E A P I C L I E N T D O M A I N I N T E R FAC E S U S E C A S E S
18. P O P U L A R A R C H I T EC T U R E S D O M A I N - DATA DATA L AY E R R E P O S I TO RY DATA S TO R E A P I C L I E N T D O M A I N I N T E R FAC E S U S E C A S E S U I V I E W M O D E L S F R AG M E N TS C U STO M V I E W S
19. P O P U L A R A R C H I T EC T U R E S U I V I E W M O D E L S F R AG M E N TS C U STO M V I E W S
20. U I V I E W M O D E L S F R AG M E N TS C U STO M V I E W S
21. U I
22. U I D O U BT S S H O U L D I H AV E O N E V I E W MO D E L FO R M U LT I P L E F R AG M E N T S ?
23. U I D O U BT S S H O U L D I H AV E O N E V I E W MO D E L FO R M U LT I P L E F R AG M E N T S ? I S I T O K TO H AV E V I E W MO D E L S FO R C U STO M V I E W S ?
24. U I D O U BT S S H O U L D I H AV E O N E V I E W MO D E L FO R M U LT I P L E F R AG M E N T S ? I S I T O K TO H AV E V I E W MO D E L S FO R C U STO M V I E W S ? S H O U L D W E S H A R E V I E W MO D E L S AC R O S S M U LT I P L E U I E L E M E N T S ?
25. I N T R O D U C I N G
26. V I E W M O D E L CO N T R AC T S I N T R O D U C I N G
27. B U T B E F O R E
28. B U T B E F O R E L E T ’ S A N A LYZ E A S I M P L E P R O B L E M
29. A R EG I ST R AT IO N F LO W
30. R EG I ST R AT IO N F LOW : F E AT U R E R EQ U I R E M E N TS
31. R EG I ST R AT IO N F LOW : F E AT U R E R EQ U I R E M E N TS U S E R N A M E
32. R EG I ST R AT IO N F LOW : F E AT U R E R EQ U I R E M E N TS E M A I L U S E R N A M E
33. R EG I ST R AT IO N F LOW : F E AT U R E R EQ U I R E M E N TS I N T E R E S TS E M A I L U S E R N A M E
34. R EG I ST R AT IO N F LOW : F E AT U R E R EQ U I R E M E N TS I N T E R E S TS E M A I L U S E R N A M E
35. B A S I C I M P L E M E N TAT I O N M U LT I - AC T IV I T Y ?
36. B A S I C I M P L E M E N TAT I O N M U LT I - AC T IV I T Y ?
37. B A S I C I M P L E M E N TAT I O N M U LT I - AC T IV I T Y ? C A L L B AC K I N T E R FAC E S
38. RegistrationActivity
39. RegistrationActivity RegistrationViewModel L I V E D ATA
40. RegistrationActivity UsernameFragment RegistrationViewModel L I V E D ATA
41. RegistrationActivity UsernameFragment UsernameCallback RegistrationViewModel L I V E D ATA
42. F E AT U R E C R E E P ! ! ! ! !
43. P E R S I S T E D R EG I S T R AT I O N P R O G R E S S U I F E AT U R E C R E E P ! ! ! ! !
44. P E R S I S T E D R EG I S T R AT I O N P R O G R E S S U I F E AT U R E C R E E P ! ! ! ! !
45. P E R S I S T E D R EG I S T R AT I O N P R O G R E S S U I F E AT U R E C R E E P ! ! ! ! !
46. R E FAC TO R I NG C A L L B AC K I N T E R FAC E S
47. R E FAC TO R I NG I N T E R FAC E C A L L B AC K S
48. R E FAC TO R I NG S H A R E D V I E W MO D E L I N T E R FAC E C A L L B AC K S
49. UsernameFragment RegistrationActivity RegistrationViewModel L I V E D ATA UsernameCallback
50. UsernameFragment RegistrationActivity RegistrationViewModel L I V E D ATA
51. UsernameFragment ProgressFragment EmailFragment InterestsFragment RegistrationActivity RegistrationViewModel L I V E D ATA
52. L IV E DATA & V I E W M O D E L R E F R E S H E R
53. L IV E DATA & V I E W MO D E L R E F R E S H E R
54. L IV E DATA & V I E W MO D E L R E F R E S H E R L IV E DATA
55. L IV E DATA W O R K S L I K E A B E H AV I O R S U B J EC T
56. L IV E DATA W O R K S L I K E A B E H AV I O R S U B J EC T E V E RY T I M E W E S U B S C R I B E TO I T, I T E M I TS T H E L AT E ST VA L U E
57. L IV E DATA W O R K S L I K E A B E H AV I O R S U B J EC T E V E RY T I M E W E S U B S C R I B E TO I T, I T E M I TS T H E L AT E ST VA L U E O B S E R VAT IO N C A N B E AT TAC H E D TO A L I F EC YC L E
58. V I E W MO D E L
59. V I E W MO D E L S H A R E V I E W MO D E L
60. V I E W MO D E L S H A R E V I E W MO D E L
61. V I E W MO D E L S H A R E V I E W MO D E L
62. V I E W MO D E L S H A R E V I E W MO D E L
63. V I E W MO D E L S H A R E V I E W MO D E L
64. V I E W MO D E L S H A R E V I E W MO D E L
65. V I E W MO D E L S H A R E V I E W MO D E L
66. V I E W MO D E L S H A R E V I E W MO D E L
67. V I E W MO D E L S H A R E V I E W MO D E L
68. V I E W MO D E L S H A R E V I E W MO D E L
69. V I E W MO D E L S H A R E V I E W MO D E L WAIT A MINUTE!!!!
70. V I E W MO D E L S H A R E V I E W MO D E L
71. V I E W MO D E L
72. V I E W MO D E L V I E W M O D E L I N STA N C E S A R E S TO R E D I N A M A P W H E R E T H E C A NO N I C A L N A M E I S A K E Y A N D T H E C L A Z Z I S T H E VA LU E
73. V I E W MO D E L V I E W M O D E L I N STA N C E S A R E S TO R E D I N A M A P W H E R E T H E C A NO N I C A L N A M E I S A K E Y A N D T H E C L A Z Z I S T H E VA LU E W H E N W E D O N ’ T F I N D A N I N S TA N C E FO R T H AT C L A S S C A N O N I C A L N A M E , W E T H E N M A K E A N E W I N STA NC E A N D A D D TO T H E M A P
74. V I E W MO D E L I F W E H AV E T H E C L A Z Z O F T H E V I E W M O D E L T H AT W E WA N T
75. V I E W MO D E L I F W E H AV E T H E C L A Z Z O F T H E V I E W M O D E L T H AT W E WA N T C A N W E PA S S T H AT I N F O R M AT IO N TO O U R F R AG M E N TS A N D H AV E I T LO O K F O R T H E V I E W M O D E L F O R T H AT C L A Z Z ?
76. V I E W MO D E L I F W E H AV E T H E C L A Z Z O F T H E V I E W M O D E L T H AT W E WA N T C A N W E PA S S T H AT I N F O R M AT IO N TO O U R F R AG M E N TS A N D H AV E I T LO O K F O R T H E V I E W M O D E L F O R T H AT C L A Z Z ? C A N W E ACC E S S T H E PA R E N T V I E W MO D E L W I T HO U T K NOW I NG W H AT T H AT PA R E N T V I E W M O D E L I S ?
77. V I E W MO D E L I F W E H AV E T H E C L A Z Z O F T H E V I E W M O D E L T H AT W E WA N T C A N W E PA S S T H AT I N F O R M AT IO N TO O U R F R AG M E N TS A N D H AV E I T LO O K F O R T H E V I E W M O D E L F O R T H AT C L A Z Z ? C A N W E ACC E S S T H E PA R E N T V I E W MO D E L W I T HO U T K NOW I NG W H AT T H AT PA R E N T V I E W M O D E L I S ?
78. V I E W MO D E L I F W E H AV E T H E C L A Z Z O F T H E V I E W M O D E L T H AT W E WA N T C A N W E PA S S T H AT I N F O R M AT IO N TO O U R F R AG M E N TS A N D H AV E I T LO O K F O R T H E V I E W M O D E L F O R T H AT C L A Z Z ? C A N W E ACC E S S T H E PA R E N T V I E W MO D E L W I T HO U T K NOW I NG W H AT T H AT PA R E N T V I E W M O D E L I S ? Y E S W E C A N
79. UsernameFragment ProgressFragment EmailFragment InterestsFragment RegistrationActivity RegistrationViewModel L I V E D ATA
80. UsernameFragment ProgressFragment EmailFragment InterestsFragment RegistrationViewModel L I V E D ATA
81. RegistrationViewModel L I V E D ATA UsernameFragment EmailFragment ProgressFragment InterestsFragment <ViewModelContract>
82. RegistrationViewModel L I V E D ATA UsernameFragment EmailFragment ProgressFragment InterestsFragment <ViewModelContract> <ViewModelContract>
83. RegistrationViewModel L I V E D ATA UsernameFragment EmailFragment ProgressFragment InterestsFragment <ViewModelContract> <ViewModelContract> <ViewModelContract>
84. RegistrationViewModel L I V E D ATA UsernameFragment EmailFragment ProgressFragment InterestsFragment <ViewModelContract> <ViewModelContract> <ViewModelContract> <ViewModelContract>
85. RegistrationViewModel L I V E D ATA UsernameFragment EmailFragment ProgressFragment InterestsFragment <ViewModelContract> <ViewModelContract> <ViewModelContract> <ViewModelContract> : UsernameFragmentViewModelContract
86. RegistrationViewModel L I V E D ATA UsernameFragment EmailFragment ProgressFragment InterestsFragment <ViewModelContract> <ViewModelContract> <ViewModelContract> <ViewModelContract> : UsernameFragmentViewModelContract : EmailFragmentViewModelContract
87. RegistrationViewModel L I V E D ATA UsernameFragment EmailFragment ProgressFragment InterestsFragment <ViewModelContract> <ViewModelContract> <ViewModelContract> <ViewModelContract> : UsernameFragmentViewModelContract : EmailFragmentViewModelContract : InterestsFragmentViewModelContract
88. RegistrationViewModel L I V E D ATA UsernameFragment EmailFragment ProgressFragment InterestsFragment <ViewModelContract> <ViewModelContract> <ViewModelContract> <ViewModelContract> : UsernameFragmentViewModelContract : EmailFragmentViewModelContract : InterestsFragmentViewModelContract : ProgressFragmentViewModelContract
89. RegistrationViewModel L I V E D ATA UsernameFragment EmailFragment ProgressFragment InterestsFragment <ViewModelContract> <ViewModelContract> <ViewModelContract> <ViewModelContract> : UsernameFragmentViewModelContract : EmailFragmentViewModelContract : InterestsFragmentViewModelContract : ProgressFragmentViewModelContract arguments.put(key, RegistrationViewModel::class.java) instantiate
90. RegistrationViewModel L I V E D ATA UsernameFragment EmailFragment InterestsFragment <ViewModelContract> <ViewModelContract> <ViewModelContract> : UsernameFragmentViewModelContract : EmailFragmentViewModelContract : InterestsFragmentViewModelContract : ProgressFragmentViewModelContract arguments.put(key, RegistrationViewModel::class.java) VMProvider.of(…).get(arguments[key]) as UsernameFragmentViewModelContract) instantiate
91. RegistrationViewModel L I V E D ATA UsernameFragment EmailFragment InterestsFragment <ViewModelContract> <ViewModelContract> <ViewModelContract> : UsernameFragmentViewModelContract : EmailFragmentViewModelContract : InterestsFragmentViewModelContract : ProgressFragmentViewModelContract ProgressFragment <ViewModelContract>
92. RegistrationViewModel L I V E D ATA UsernameFragment EmailFragment InterestsFragment <ViewModelContract> <ViewModelContract> <ViewModelContract> : UsernameFragmentViewModelContract : EmailFragmentViewModelContract : InterestsFragmentViewModelContract : ProgressFragmentViewModelContract ProgressFragment <ViewModelContract>
93. RegistrationViewModel L I V E D ATA UsernameFragment EmailFragment InterestsFragment <ViewModelContract> <ViewModelContract> <ViewModelContract> : UsernameFragmentViewModelContract : EmailFragmentViewModelContract : InterestsFragmentViewModelContract : ProgressFragmentViewModelContract ProgressFragment <ViewModelContract>
94. RegistrationViewModel L I V E D ATA UsernameFragment EmailFragment InterestsFragment <ViewModelContract> <ViewModelContract> <ViewModelContract> : UsernameFragmentViewModelContract : EmailFragmentViewModelContract : InterestsFragmentViewModelContract : ProgressFragmentViewModelContract ProgressFragment <ViewModelContract>
95. RegistrationViewModel L I V E D ATA UsernameFragment EmailFragment InterestsFragment <ViewModelContract> <ViewModelContract> <ViewModelContract> : UsernameFragmentViewModelContract : EmailFragmentViewModelContract : InterestsFragmentViewModelContract : ProgressFragmentViewModelContract ProgressFragment <ViewModelContract>
96. RegistrationViewModel L I V E D ATA UsernameFragment EmailFragment InterestsFragment <ViewModelContract> <ViewModelContract> <ViewModelContract> : UsernameFragmentViewModelContract : EmailFragmentViewModelContract : InterestsFragmentViewModelContract : ProgressFragmentViewModelContract ProgressFragment <ViewModelContract>
97. RegistrationViewModel L I V E D ATA RegistrationActivity
99. RegistrationMasterViewModel L I V E D ATA RegistrationMasterFragment
100. RegistrationMasterViewModel L I V E D ATA RegistrationMasterFragment
101. UsernameFragment EmailFragment InterestsFragment <ViewModelContract> <ViewModelContract> <ViewModelContract> : UsernameFragmentViewModelContract : EmailFragmentViewModelContract : InterestsFragmentViewModelContract : ProgressFragmentViewModelContract ProgressFragment <ViewModelContract> RegistrationMasterViewModel L I V E D ATA
102. UsernameFragment EmailFragment InterestsFragment <ViewModelContract> <ViewModelContract> <ViewModelContract> : UsernameFragmentViewModelContract : EmailFragmentViewModelContract : InterestsFragmentViewModelContract : ProgressFragmentViewModelContract ProgressFragment <ViewModelContract> RegistrationMasterViewModel L I V E D ATA arguments.put(key, RegistrationMasterViewModel::class.java) instantiate
103. A R EG I ST R AT I O N F LO W W I T H V I E W M O D E L CO N T R AC T S
104. ProgressFragment RegistrationActivity RegistrationViewModel L I V E D ATA
105. ProgressFragment RegistrationActivity RegistrationViewModel L I V E D ATA
106. ProgressFragment RegistrationActivity RegistrationViewModel L I V E D ATA
107. ProgressFragment L I V E D ATA RegistrationActivity RegistrationViewModel L I V E D ATA 1 ProgressViewModelContract
108. ProgressFragment L I V E D ATA RegistrationActivity RegistrationViewModel L I V E D ATA 1 2 ProgressViewModelContract
109. ProgressFragment L I V E D ATA RegistrationActivity RegistrationViewModel L I V E D ATA 1 2 3 ProgressViewModelContract
110. ProgressFragment ProgressViewModelContract L I V E D ATA RegistrationActivity RegistrationViewModel L I V E D ATA 1 2 3 4
111. P R OG R E S S V I E W MO D E L CO N T R AC T
112. P R OG R E S S V I E W MO D E L CO N T R AC T
113. P R OG R E S S V I E W MO D E L CO N T R AC T
114. U S I NG T H E V I E W M O D E L CO N T R AC T
115. U S I NG T H E V I E W M O D E L CO N T R AC T
116. U S I NG T H E V I E W M O D E L CO N T R AC T
117. U S I NG T H E V I E W M O D E L CO N T R AC T
118. R E T R I E V I N G A V I E W MO D E L CO N T R AC T
119. R E T R I E V I N G A V I E W MO D E L CO N T R AC T
120. R E T R I E V I N G A V I E W MO D E L CO N T R AC T
121. R E T R I E V I N G A V I E W MO D E L CO N T R AC T
122. E N FO R C I NG V I E W MO D E L CO N T R AC T U SAG E
123. E N FO R C I NG V I E W MO D E L CO N T R AC T U SAG E
124. R EG I ST E R I NG T H E V I E W MO D E L K E Y
125. C R E AT I N G T H E F R AG M E N T
126. C R E AT I N G T H E F R AG M E N T
127. C R E AT I N G T H E F R AG M E N T
128. I M P L E M E N T I N G T H E CO N T R AC T
129. I M P L E M E N T I N G T H E CO N T R AC T
130. I M P L E M E N T I N G T H E CO N T R AC T
131. V I E W MO D E L CO N T R AC TS , A DVA NC E D PA R E N T F R AG M E N T S & AC T IV I T I E S M ATC H BY L A Z Y S T Y L E
132. V I E W MO D E L CO N T R AC TS , A DVA NC E D
133. V I E W MO D E L CO N T R AC TS , A DVA NC E D
134. TA K E AWAYS
135. TA K E AWAYS Decouples Fragments
136. TA K E AWAYS Decouples Fragments Reduces Scope
137. TA K E AWAYS Decouples Fragments Reduces Scope Improves reusability
138. TA K E AWAYS
139. MV V M & N E S T E D F R AG M E N T/ V I E W S - V I E W M O D E L CO N T R AC TS M A R C O S DA M A S C E N O S R . A N D R O I D E NG I N E E R @marcospaulosd B R E T E R I C K S O N A N D R O I D E NG I N E E R I NG M A N AG E R linkedin.com/in/breterickson/
140. MV V M & N E S T E D F R AG M E N T/ V I E W S - V I E W M O D E L CO N T R AC TS M A R C O S DA M A S C E N O S R . A N D R O I D E NG I N E E R @marcospaulosd B R E T E R I C K S O N A N D R O I D E NG I N E E R I NG M A N AG E R linkedin.com/in/breterickson/ T H A N K YO U
141. MV V M & N E S T E D F R AG M E N T/ V I E W S - V I E W M O D E L CO N T R AC TS M A R C O S DA M A S C E N O S R . A N D R O I D E NG I N E E R @marcospaulosd B R E T E R I C K S O N A N D R O I D E NG I N E E R I NG M A N AG E R linkedin.com/in/breterickson/ T H A N K YO U http://bit.ly/
 ViewModelContracts