Android Architecture Components

Slides from my presentation on AAC at,

Android Summit, Washington D.C. 2017, 24-Aug-2017
- http://androidsummit.org/

Transcript

1. Viraj Tank Sociomantic Labs @viraj49
2. Viraj Tank Sociomantic Labs @viraj49
4. God Activity Problem
5. Rise of Architectures
6. God P/VM Problem
7. Clean Architecture
8. Lifecycle Question
9. Bind/Subscribe - onResume/onStart UnBind/Dispose - onPause/onStop
10. View Reloading Problem
11. RunTime Config Change e.g. Orientation, Keyboard availability, Language, Docking etc Android restarts running Activity
12. Data call may get interrupted Context Leak View state management
14. - Lifecycle changes - Configuration changes Reloading the view Data call may get interrupted Context Leak View state management Problem Summary
15. MVP Activity/Fragment
20. Bind - onStart Dispose - onDestroy* UnBind - onStop Activity !isConfigurationChanging
21. Bind - onStart Dispose - onDestroy UnBind - onStop Fragment
23. RxJava Subject Hot Observable Behavior / Publish RxRelay
25. Activity class MyActiviy : Activity() { private val myPresenterFactory = MyPresenterFactory() private lateinit var myPresenter: MyPresenter override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) myPresenter = myPresenterFactory.getPresenter() } class MyActiviy : Activity() { private val myPresenterFactory = MyPresenterFactory() private lateinit var myPresenter: MyPresenter override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) myPresenter = myPresenterFactory.getPresenter() } override fun onStart() { super.onStart() myPresenter.bind(this) } override fun onStop() { myPresenter.unBind() super.onStop() } class MyActiviy : Activity() { private val myPresenterFactory = MyPresenterFactory() private lateinit var myPresenter: MyPresenter override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) myPresenter = myPresenterFactory.getPresenter() } override fun onStart() { super.onStart() myPresenter.bind(this) } override fun onStop() { myPresenter.unBind() super.onStop() } override fun onDestroy() { if (!isChangingConfigurations) { myPresenter.dispose() } super.onDestroy() } }
26. Fragment class MyFragment : Fragment() { private val myPresenter = MyPresenter() override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) retainInstance = true } class MyFragment : Fragment() { private val myPresenter = MyPresenter() override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) retainInstance = true } override fun onStart() { super.onStart() myPresenter.bind(this) } override fun onStop() { myPresenter.unBind() super.onStop() } class MyFragment : Fragment() { private val myPresenter = MyPresenter() override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) retainInstance = true } override fun onStart() { super.onStart() myPresenter.bind(this) } override fun onStop() { myPresenter.unBind() super.onStop() } override fun onDestroy() { myPresenter.dispose() super.onDestroy() } }
27. Presenter class MyPresenter { private val hotObservable = BehaviorSubject.create<Model>() private val viewSubscriptions = CompositeDisposable() private val dataSubscriptions = CompositeDisposable() class MyPresenter { private val hotObservable = BehaviorSubject.create<Model>() private val viewSubscriptions = CompositeDisposable() private val dataSubscriptions = CompositeDisposable() fun bind(view: MyFragment) { viewSubscriptions.add(hotObservable .observeOn(AndroidSchedulers.mainThread()) .subscribe({ this.view.updateView(it) })) } class MyPresenter { private val hotObservable = BehaviorSubject.create<Model>() private val viewSubscriptions = CompositeDisposable() private val dataSubscriptions = CompositeDisposable() fun bind(view: MyFragment) { viewSubscriptions.add(hotObservable .observeOn(AndroidSchedulers.mainThread()) .subscribe({ this.view.updateView(it) })) } fun unBind() { viewSubscriptions.clear() this.view = null }
28. Presenter class MyPresenter { fun getData() { dataSubscriptions.add(myDataSource.getData()) .subscribeOn(Schedulers.computation()) .observeOn(Schedulers.computation()) .subscribe({ modelData -> hotObservable.onNext(modelData) }) } class MyPresenter { init { getData() } fun getData() { dataSubscriptions.add(myDataSource.getData()) .subscribeOn(Schedulers.computation()) .observeOn(Schedulers.computation()) .subscribe({ modelData -> hotObservable.onNext(modelData) }) } class MyPresenter { init { getData() } fun getData() { dataSubscriptions.add(myDataSource.getData()) .subscribeOn(Schedulers.computation()) .observeOn(Schedulers.computation()) .subscribe({ modelData -> hotObservable.onNext(modelData) }) } fun dispose() { dataSubscriptions.dispose() } }
29. Reloading the view Data call may get interrupted Context Leak View state management
30. View State Management View data State changing action One time action
31. View Data
32. State Changing Action
33. Unidirectional Dataflow data class MyViewState(val myData: String = "", val loadingState: Boolean = false) data class MyViewState(val myData: String = "", val loadingState: Boolean = false) class MyPresenter { private var myViewState = MyViewState() private val hotObservable = BehaviorSubject.create<MyViewState>() data class MyViewState(val myData: String = "", val loadingState: Boolean = false) class MyPresenter { private var myViewState = MyViewState() private val hotObservable = BehaviorSubject.create<MyViewState>() fun getData() { myViewState = myViewState.copy(myData = data, loadingState = fals hotObservable.onNext(myViewState) } }
34. One Time Action
36. isConsumed data class MyViewState(val isConsumed: Boolean = true, val errorMessage: String = "") data class MyViewState(val isConsumed: Boolean = true, val errorMessage: String = "") class MyPresenter { private var myViewState = MyViewState() private val hotObservable = BehaviorSubject.create<MyViewState>() data class MyViewState(val isConsumed: Boolean = true, val errorMessage: String = "") class MyPresenter { private var myViewState = MyViewState() private val hotObservable = BehaviorSubject.create<MyViewState>() fun getData() { myViewState = myViewState.copy(isConsumed = false, errorMessage = "Error") hotObservable.onNext(myViewState) } data class MyViewState(val isConsumed: Boolean = true, val errorMessage: String = "") class MyPresenter { private var myViewState = MyViewState() private val hotObservable = BehaviorSubject.create<MyViewState>() fun getData() { myViewState = myViewState.copy(isConsumed = false, errorMessage = "Error") hotObservable.onNext(myViewState) } class MyFragment : Fragment() { fun updateView(myViewState: MyViewState) { if (!myViewState.isConsumed) { showError() myPresenter.errorConsumed() } } } data class MyViewState(val isConsumed: Boolean = true, val errorMessage: String = "") class MyPresenter { private var myViewState = MyViewState() private val hotObservable = BehaviorSubject.create<MyViewState>() fun getData() { myViewState = myViewState.copy(isConsumed = false, errorMessage = "Error") hotObservable.onNext(myViewState) } fun errorConsumed() { myViewState = myViewState.copy(true, "") hotObservable.onNext(myViewState) } } class MyFragment : Fragment() { fun updateView(myViewState: MyViewState) { if (!myViewState.isConsumed) { showError() myPresenter.errorConsumed() } } }
37. MVP + Subjects MVVM + Subjects
38. Android Architecture Components Lifecycle ViewModel LiveData Room
39. AAC- core concept
41. Should I use ViewModel with MVP? NO
42. Can I use ViewModel with MVP? YES
43. AAC - ViewModel Retained Fragment Storage Lifecycle Aware onDestroy() clean up
44. AAC - LiveData ~ Hot Observables Lifecycle Aware STARTED or RESUMED onDestroy() clean up
45. Activity class MyActiviy : LifecycleActivity() { private val myViewModelFactory = MyViewModelFactory() private lateinit var myViewModel: MyViewModel override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) myViewModel = ViewModelProviders.of(this, myViewModelFactory) .get(MyViewModel::class.java) myViewModel.myLiveData.observe(this, Observer { /* Update View */ }) } }
46. Fragment class MyFragment : LifecycleFragment() { private val myViewModelFactory = MyViewModelFactory() private lateinit var myViewModel: MyViewModel override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) myViewModel = ViewModelProviders.of(this, myViewModelFactory) .get(MyViewModel::class.java) myViewModel.myLiveData.observe(this, Observer { /* Update View */ }) } }
47. ViewModel class MyViewModel : ViewModel() { private val dataSubscription = CompositeDisposable() private var myViewState = MyViewState() val myLiveData = MutableLiveData<MyViewState>() init { getData() } fun getData() { dataSubscriptions.add(myDataSource.getData()) .subscribeOn(Schedulers.computation()) .observeOn(Schedulers.computation()) .subscribe({ data -> myViewState = myViewState.copy(myData = data) myLiveData.postValue(myViewState) }) } override fun onCleared() { dataSubscription.dispose() super.onCleared() } }
48. Summary
49. - Lifecycle changes - Configuration changes Reloading the view Data call may get interrupted Context Leak Recreating view state
50. MVP - Subject based solution - AAC based solution MVVM - AAC based solution
51. Thanks speakerdeck.com/viraj49 github.com/viraj49 twitter.com/viraj49