Android Architecture ComponentのLifecyle対応コンポーネントのおさらい / Review of Lifecyle aware components of AAC

Android研究&発表会#4で発表した資料です！
https://arap.connpass.com/event/161452/

リンク集
- Android Architecture Component
https://www.youtube.com/watch?v=LmkKFCfmnhQ&feature=youtu.be&hl=ja
https://www.youtube.com/watch?v=pErTyQpA390

- Lifecycle 2.2.0-alpha03のリリースノート
https://developer.android.com/jetpack/androidx/releases/lifecycle#2.2.0-alpha03

- Lifecycle-Aware Componentsのコードラボ
https://codelabs.developers.google.com/codelabs/android-lifecycles/#0

- zipLiveData
https://medium.com/@gauravgyal/combine-results-from-multiple-async-requests-90b6b45978f7

- Eventクラス(LiveDataのラッパークラス)
https://medium.com/androiddevelopers/livedata-with-snackbar-navigation-and-other-events-the-singleliveevent-case-ac2622673150

- 資料に使ったコードはこのあたり
https://github.com/kwmt/android-lifecycles/tree/master/app/src/main/java/com/example/android/lifecycles/arap_osaka

- ブログ
https://kwmt27.net/2019/09/19/android-lifecycle-codelab/

Transcript

1. Android Architecture Componentͷ LifecyleରԠίϯϙʔωϯτͷ ͓͞Β͍ Androidݚڀ&ൃදձ #4 2020/01/25
2. • Տຊ ହ޹(͔Θ΋ͱ ΍͔ͨ͢) • ॴଐɿגࣜձࣾ tech vein 
 (େࡕࢢதԝ۠ຊொ) • ϞόΠϧΞϓϦΤϯδχΞ
 (AndroidଟΊɺiOS΋ŧŔŕŪũƄŝſ) • GitHub: kwmt ɺtwitter: kwmt27 • Google I/O2018 ॳࢀՃ • ෱Ԭग़਎ • ΫϥϑτϏʔϧ޷͖ ࣗݾ঺հ
3. • Android Architecture Componentͱ͸ʁ • ViewModelͰ؆୯ը໘ճస • LiveDataΛ࢖ͬͯUIΛߋ৽ • LifecycleͰActivity΍FragmentΛεοΩϦ • ViewModelͷڞ༗ • Tips • ·ͱΊ ΞδΣϯμ
4. Android Architecture Componentͱ͸ https://www.youtube.com/watch?v=LmkKFCfmnhQ&feature=youtu.be&hl=ja
5. Android Architecture Componentͱ͸ https://www.youtube.com/watch?v=pErTyQpA390
6. ViewModel, LiveData, Lifecycle ࠓ೔ͷओ໾
7. ViewModelͰ؆୯ը໘ճస
8. ՝୊ Activity ViewModelΛ࢖Θͣ ࣮૷ͨ͠৔߹ ը໘ճసͷͱ͖ɺ ʢͳʹ΋͠ͳ͍ͱʣ λΠϚʔ͕ΫϦΞ͞ΕΔ ※savedInstanceStateΛ࢖͑͹ ΫϦΞ͞Εͳ͍Α͏ʹ͢Δ͜ͱ͸Ͱ͖·͕͢ɺ ͜͜Ͱ͸ߟ͑·ͤΜɻ ྫɿλΠϚʔΞϓϦ
9. ՝୊ Activity ViewModelΛ࢖Θͣ ࣮૷ͨ͠৔߹ ը໘ճసͷͱ͖ɺ ʢͳʹ΋͠ͳ͍ͱʣ λΠϚʔ͕ΫϦΞ͞ΕΔ ※savedInstanceStateΛ࢖͑͹ ΫϦΞ͞Εͳ͍Α͏ʹ͢Δ͜ͱ͸Ͱ͖·͕͢ɺ ͜͜Ͱ͸ߟ͑·ͤΜɻ ྫɿλΠϚʔΞϓϦ
10. ViewModelΛ࢖͏ͱ Activity viewModel ը໘ճసͷͱ͖ɺ λΠϚʔ͕ΫϦΞ͞Εͳ͍Α͏ʹ ؆୯ʹͰ͖Δ ViewModel timer
11. ViewModelΛ࢖͏ͱ Activity viewModel ը໘ճసͷͱ͖ɺ λΠϚʔ͕ΫϦΞ͞Εͳ͍Α͏ʹ ؆୯ʹͰ͖Δ ViewModel timer
12. ViewModelͷੜଘظؒ ࣌ؒ Activity ViewModel
13. ViewModelͷੜଘظؒ ࣌ؒ ىಈ Activity ViewModel
14. ViewModelͷੜଘظؒ onCreate ࣌ؒ ViewModelੜ੒ onStart onResume ىಈ Activity ViewModel
15. ViewModelͷੜଘظؒ onCreate ࣌ؒ ViewModelੜ੒ onStart onResume ىಈ ճస Activity ViewModel
16. ViewModelͷੜଘظؒ onCreate ࣌ؒ ViewModelੜ੒ onStart onResume onPause onStop onDestroy onCreate onStart onResume ىಈ ճస Activity ViewModel
17. ViewModelͷੜଘظؒ onCreate ࣌ؒ ViewModelੜ੒ onStart onResume onPause onStop onDestroy onCreate onStart onResume ىಈ ճస όοΫΩʔͰΞϓϦऴྃ Activity ViewModel
18. ViewModelͷੜଘظؒ onCreate ࣌ؒ ViewModelੜ੒ onStart onResume onPause onStop onDestroy onCreate onStart onResume onPause onStop onDestroy ىಈ ճస όοΫΩʔͰΞϓϦऴྃ onCleared Activity ViewModel
19. ViewModelͷੜଘظؒ onCreate ࣌ؒ ViewModelੜ੒ onStart onResume onPause onStop onDestroy onCreate onStart onResume onPause onStop onDestroy ىಈ ճస όοΫΩʔͰΞϓϦऴྃ onCleared Activity ViewModel
20. override fun onCreate(savedInstanceState: Bundle?) { // লུ val chronometer = findViewById(R.id.chronometer) val startTime = viewModel.startTime if (startTime == null) { val time = SystemClock.elapsedRealtime() viewModel.startTime = time chronometer.base = time } else { chronometer.base = startTime } chronometer.start() } Activity class ChronoViewModel: ViewModel() { var startTime: Long? = null } ViewModel
21. • Kotlin ϓϩύςΟσϦήʔτΛ࢖͏ํ๏ ViewModelΠϯελϯεͷऔಘํ๏ (஫ҙ)fragment-ktxͷ1.1.0Ҏ্Λ࢖͏ඞཁ͋Γ val viewModel by viewModels<MyViewModel>() https://developer.android.com/jetpack/androidx/releases/lifecycle#2.2.0-alpha03 ViewModelProviders.of(this) .get(MyViewModel::class.java) • ViewModelProviderΛ࢖͏ํ๏ viewModel = ViewModelProvider(this) .get(MyViewModel::class.java)
22. • Kotlin ϓϩύςΟσϦήʔτΛ࢖͏ํ๏ ViewModelΠϯελϯεͷऔಘํ๏ (஫ҙ)fragment-ktxͷ1.1.0Ҏ্Λ࢖͏ඞཁ͋Γ val viewModel by viewModels<MyViewModel>() https://developer.android.com/jetpack/androidx/releases/lifecycle#2.2.0-alpha03 ViewModelProviders.of(this) .get(MyViewModel::class.java) • ViewModelProviderΛ࢖͏ํ๏ viewModel = ViewModelProvider(this) .get(MyViewModel::class.java) 2.2.0-alpha03͔ΒDeprecated
23. • Activity΍FragmentͷϥΠϑαΠΫϧશମͰσʔλΛอ࣋ Ͱ͖Δ • Activity΍FragmentΑΓੜଘظ͕ؒ௕͍ΦϒδΣΫτ • ViewModelΫϥεͷ࡞੒͸ɺViewModel()Λܧঝ͢Δ͚ͩ • ViewModelΠϯελϯεΛऔಘ͢Δʹ͸ɺ
 KotlinϓϩύςΟσϦήʔτͱViewModelProviderΛ࢖͏ ํ๏͕͋Δ ViewModel ·ͱΊ
24. LiveDataΛ࢖ͬͯUIΛߋ৽
25. • ઌఔͷλΠϚʔΞϓϦͰɺ
 UIΛ1ඵִؒͰ
 ʮʙඵܦաʯ
 ͱද͍ࣔͨ͠ • ͔ͭɺը໘ճస΋ߟྀ͍ͨ͠ ͜͜Ͱղܾ͍ͨ͠՝୊
26. • ઌఔͷλΠϚʔΞϓϦͰɺ
 UIΛ1ඵִؒͰ
 ʮʙඵܦաʯ
 ͱද͍ࣔͨ͠ • ͔ͭɺը໘ճస΋ߟྀ͍ͨ͠ ͜͜Ͱղܾ͍ͨ͠՝୊
27. ViewModelʹߋ৽͍ͨ͠ViewΛ ࣋ͨͤͨΒ͍͍Μ͡Όʁ class MyViewModel : ViewModel() { val initialTime = SystemClock.elapsedRealtime() private val timer = Timer() var timerTextView: TextView? = null init{ timer.scheduleAtFixedRate(object : TimerTask() { override fun run() { timerTextView?.text = "$ඵ਺ ඵܦա" } }, 1000, 1000) } }
28. ViewModelʹߋ৽͍ͨ͠ViewΛ ࣋ͨͤͨΒ͍͍Μ͡Όʁ class MyViewModel : ViewModel() { val initialTime = SystemClock.elapsedRealtime() private val timer = Timer() var timerTextView: TextView? = null init{ timer.scheduleAtFixedRate(object : TimerTask() { override fun run() { timerTextView?.text = "$ඵ਺ ඵܦա" } }, 1000, 1000) } } • ΞϓϦऴྃ࣌ʹϝϞϦϦʔΫ͢ΔͷͰɺͰ͖·ͤΜɻ
29. ViewModelʹߋ৽͍ͨ͠ViewΛ ࣋ͨͤͨΒ͍͍Μ͡Όʁ class MyViewModel : ViewModel() { val initialTime = SystemClock.elapsedRealtime() private val timer = Timer() var timerTextView: TextView? = null init{ timer.scheduleAtFixedRate(object : TimerTask() { override fun run() { timerTextView?.text = "$ඵ਺ ඵܦա" } }, 1000, 1000) } } • ΞϓϦऴྃ࣌ʹϝϞϦϦʔΫ͢ΔͷͰɺͰ͖·ͤΜɻ AACͷLiveDataΛ࢖͍·͢ʂ
30. LiveDataΛ࢖͏ class MyViewModel : ViewModel() { val initialTime = SystemClock.elapsedRealtime() private val timer = Timer() private val elapsedTime = MutableLiveData<Long>() fun getElapsedTime(): LiveData<Long> = elapsedTime init{ timer.scheduleAtFixedRate(object : TimerTask() { override fun run() { elapsedTime.postValue(ඵ਺) } }, 1000, 1000) } } viewModel.getElapsedTime()
 .observe(this, Observer { timerTextView.text = "${t}ඵܦա" }) • Activityଆ
31. LiveDataΛ࢖͏ class MyViewModel : ViewModel() { val initialTime = SystemClock.elapsedRealtime() private val timer = Timer() private val elapsedTime = MutableLiveData<Long>() fun getElapsedTime(): LiveData<Long> = elapsedTime init{ timer.scheduleAtFixedRate(object : TimerTask() { override fun run() { elapsedTime.postValue(ඵ਺) } }, 1000, 1000) } } viewModel.getElapsedTime()
 .observe(this, Observer { timerTextView.text = "${t}ඵܦա" }) • Activityଆ
32. LiveDataΛ࢖͏ ViewModel Activity viewModel elapsedTime timerTextView.text
33. LiveDataΛ࢖͏ ViewModel Activity viewModel elapsedTime observeͰ؂ࢹ timerTextView.text
34. LiveDataΛ࢖͏ ViewModel Activity viewModel elapsedTime observeͰ؂ࢹ 1ඵ͝ͱʹߋ৽ timerTextView.text
35. LiveDataΛ࢖͏ ViewModel Activity viewModel elapsedTime observeͰ؂ࢹ 1ඵ͝ͱʹߋ৽ timerTextView.text ௨஌
36. • ViewModelʹViewΛ࣋ͨͤΔͷ͸ɺ
 ϝϞϦϦʔΫ͢ΔͷͰμϝ • ViewModelʹLiveDataΛ࣋ͨͤͯɺActivity΍Fragment͔ Β؂ࢹ(observe)͠ɺViewModel͔Β௨஌͢Δ LiveData ·ͱΊ
37. LifecycleͰActivity΍FragmentΛεοΩϦ
38. • ͨͱ͑͹ɺݱࡏ஍Λऔಘ͢ΔͨΊʹɺ LocationManager Λ࢖͏ͱ͠·͢ɻ
 ͜ͷΑ͏ͳAPIΛ࢖͏ͨΊʹ͸ɺ
 onResumeͰॳظԽɾsubscribeͨ͠Γ
 onPauseͰετοϓͨ͠Γɺunsubscribe͢Δ͜ͱ͕ඞཁ Ͱ͢ɻ ͜͜Ͱղܾ͍ͨ͠՝୊
39. ͜͜Ͱղܾ͍ͨ͠՝୊ Activity override fun onResume(){ locationManager.requestLocationUpdates(লུ) } override fun onPause(){ locationManager.removeUpdates(লུ) } • AndroidͷϥΠϒϥϦ΍API͸͜ͷΑ͏ͳॲཧΛ͢Δ΋ͷ ͕ଟ͍ͷͰɺActivity΍FragmentΫϥε͕๲ΒΜͰ͖ͯɺ ಡΈʹ͘͘ͳΓ·͢ɻ
40. Activity override fun onCreate(){ LocationLifecyle(this) } Lifecycle class LocationLifecycle(lifecycleOwner: LifecycleOwner) ɹɹɹ: LifecycleObserver { init { lifecycleOwner.lifecycle.addObserver(this) } @OnLifecycleEvent(ON_RESUME) fun addLocationListener() { locationManager.requestLocationUpdates(লུ) } @OnLifecycleEvent(ON_PAUSE) fun removeLocationListener() { locationManager.removeUpdates(লུ) } }
41. Activity override fun onCreate(){ LocationLifecyle(this) } Lifecycle class LocationLifecycle(lifecycleOwner: LifecycleOwner) ɹɹɹ: LifecycleObserver { init { lifecycleOwner.lifecycle.addObserver(this) } @OnLifecycleEvent(ON_RESUME) fun addLocationListener() { locationManager.requestLocationUpdates(লུ) } @OnLifecycleEvent(ON_PAUSE) fun removeLocationListener() { locationManager.removeUpdates(লུ) } } interfaceΛ࣮૷
42. Activity override fun onCreate(){ LocationLifecyle(this) } Lifecycle class LocationLifecycle(lifecycleOwner: LifecycleOwner) ɹɹɹ: LifecycleObserver { init { lifecycleOwner.lifecycle.addObserver(this) } @OnLifecycleEvent(ON_RESUME) fun addLocationListener() { locationManager.requestLocationUpdates(লུ) } @OnLifecycleEvent(ON_PAUSE) fun removeLocationListener() { locationManager.removeUpdates(লུ) } } interfaceΛ࣮૷ observerΛొ࿥
43. Activity override fun onCreate(){ LocationLifecyle(this) } Lifecycle class LocationLifecycle(lifecycleOwner: LifecycleOwner) ɹɹɹ: LifecycleObserver { init { lifecycleOwner.lifecycle.addObserver(this) } @OnLifecycleEvent(ON_RESUME) fun addLocationListener() { locationManager.requestLocationUpdates(লུ) } @OnLifecycleEvent(ON_PAUSE) fun removeLocationListener() { locationManager.removeUpdates(লུ) } } interfaceΛ࣮૷ observerΛొ࿥ ϥΠϑαΠΫϧʹґ ଘ͍ͨ͠ϝιουʹ ΞϊςʔγϣϯΛͭ ͚Δ
44. • AndroidϥΠϑαΠΫϧʹؔΘΔAPI΍ϥΠϒϥϦΛ࢖͏ ࣌ʹɺAAC LifecycleΛ࢖͏ͱActivity΍FragmentҎ֎ͷ ΫϥεͰϥΠϑαΠΫϧݕ஌͕Ͱ͖Δɻ Lifecycle ·ͱΊ
45. ViewModelͷڞ༗
46. • Fragment͔ΒActivityʹͳʹ͔௨஌͍ͨͬͯ͠໘౗ͩͬͨ ΑͶʁ ͜͜Ͱղܾ͍ͨ͠՝୊
47. class FugaFragment : Fragment() { interface OnClickListener { fun onClick() } private var onClickListener: OnClickListener? = null // লུ override fun onActivityCreated { // লུ onClickListener = requireActivity() as? OnClickListener // ϘλϯͳͲͷΫϦοΫΠϕϯτͰonClickΛݺͿ onClickListener?.onClick() } } class HogeActivity : AppCompatActivity(), FugaFragment.OnClickListener { // লུ override fun onClick() { // ͳʹ͔ } }
48. class FugaFragment : Fragment() { interface OnClickListener { fun onClick() } private var onClickListener: OnClickListener? = null // লུ override fun onActivityCreated { // লུ onClickListener = requireActivity() as? OnClickListener // ϘλϯͳͲͷΫϦοΫΠϕϯτͰonClickΛݺͿ onClickListener?.onClick() } } class HogeActivity : AppCompatActivity(), FugaFragment.OnClickListener { // লུ override fun onClick() { // ͳʹ͔ } } ௨஌༻interfaceΛఆٛ ϑΟʔϧυʹม਺༻ҙ Activity͕interfaceΛ࣮૷ͯͨ͠ΒΩϟετ ௨஌༻ͷinterfaceΛ࣮૷
49. • ActivityͱFragmentͰViewModelΛڞ༗ͯ͠ɺ
 ಉ͜͡ͱΛ΍ͬͯΈΔ ViewModelΛڞ༗
50. class HogeActivity : AppCompatActivity() { private val viewModel by viewModels<HogeViewModel>() override fun onCreate(savedInstanceState: Bundle?) { // লུ viewModel.clickEvent.observe(this) { textView.text = it } } } private val viewModel by viewModels<HogeViewModel> ({ requireActivity() }) viewModel.onClick() class HogeViewModel : ViewModel() { val clickEvent = MutableLiveData<String>() fun onClick() { clickEvent.value = "Ϙλϯ͕ԡ͞ΕͨΑ" } }
51. ͜ΕΛಈ͔͢ͱ
52. ͜ΕΛಈ͔͢ͱ
53. • Fragment͔ΒActivity΁ͷ௨஌͕؆୯ • (͜͜Ͱ͸આ໌ͯ͠·ͤΜ͕)Fragmentಉ࢜ͷڞ༗΋Մೳ ViewModelڞ༗ͷ·ͱΊ
54. ͜͜·Ͱ͸΄΅Codelabͷ಺༰ https://codelabs.developers.google.com/codelabs/android-lifecycles/#0
55. Tips
56. • 2ͭͷLiveDataΛ݁߹͍ͨ͠ • LiveDataͷൃՐΛҰ౓͚ͩʹ͍ͨ͠ Tips
57. • 2ͭͷLiveDataΛ݁߹͍ͨ͠ • LiveDataͷൃՐΛҰ౓͚ͩʹ͍ͨ͠ Tips
58. 2ͭͷLiveDataΛ݁߹͍ͨ͠
59. MediatorLiveDataΛ࢖͏ class ZipLIveDataViewModel : ViewModel() { val editText1 = MutableLiveData<String>() val editText2 = MutableLiveData<String>() val isEnabled = MediatorLiveData<Boolean>() init { val observer = Observer<String> { isEnabled.value = editText1.value?.isNotEmpty() ?: false && editText2.value?.isNotEmpty() ?: false } isEnabled.addSource(editText1, observer) isEnabled.addSource(editText2, observer) } }
60. MediatorLiveDataͷϥούʔؔ਺Λ࡞Δ fun <A, B> zipLiveData(a: LiveData<A>, b: LiveData<B>): LiveData<Pair<A, B>> { return MediatorLiveData<Pair<A, B>>().apply { var lastA: A? = null var lastB: B? = null fun update() { val localLastA = lastA val localLastB = lastB if (localLastA != null && localLastB != null) { this.value = Pair(localLastA, localLastB) } } addSource(a) { lastA = it update() } addSource(b) { lastB = it update() } } } https://medium.com/@gauravgyal/combine-results-from-multiple-async-requests-90b6b45978f7
61. MediatorLiveDataͷϥούʔؔ਺Λ࢖͏ class ZipLIveDataViewModel : ViewModel() { val editText1 = MutableLiveData<String>() val editText2 = MutableLiveData<String>() val isEnabled: LiveData<Boolean> = zipLiveData(editText1, editText2) .map { (t1, t2) -> t1.isNotEmpty() && t2.isNotEmpty() } }
62. ൺ΂Δ class ZipLIveDataViewModel : ViewModel() { val editText1 = MutableLiveData<String>() val editText2 = MutableLiveData<String>() val isEnabled: LiveData<Boolean> = zipLiveData(editText1, editText2) .map { (t1, t2) -> t1.isNotEmpty() && t2.isNotEmpty() } } class ZipLIveDataViewModel : ViewModel() { val editText1 = MutableLiveData<String>() val editText2 = MutableLiveData<String>() val isEnabled = MediatorLiveData<Boolean>() init { val observer = Observer<String> { isEnabled.value = editText1.value?.isNotEmpty() ?: false && editText2.value?.isNotEmpty() ?: false } isEnabled.addSource(editText1, observer) isEnabled.addSource(editText2, observer) } }
63. ಈ͔͢
64. ಈ͔͢
65. • 2ͭͷLiveDataΛ݁߹͍ͨ͠ • LiveDataͷൃՐΛҰ౓͚ͩʹ͍ͨ͠ Tips
66. • ը໘ભҠʹLiveDataΛ࢖͏ͱɺ໭Δ͜ͱ͕Ͱ͖ͳ͍ LiveDataͷൃՐΛҰ౓͚ͩʹ͍ͨ͠
67. ભҠݩʹ໭Εͳ͍࣮૷ྫ override fun onViewCreated() { viewModel.nextLiveData .observe(viewLifecycleOwner) { nextViewType -> // ը໘ભҠ͢Δ } button .setOnClickListener{viewModel.onClickNextButton()}
 } fun onClickNextButton() { // APIϨεϙϯεͷ݁ՌʹΑͬͯɺը໘ભҠΛม͍͑ͨ৔߹ val data = repository.fetchData() // লུ _nextLiveData.value = nextType } Fragment ViewModel
68. ભҠݩʹ໭Εͳ͍࣮૷ྫ override fun onViewCreated() { viewModel.nextLiveData .observe(viewLifecycleOwner) { nextViewType -> // ը໘ભҠ͢Δ } button .setOnClickListener{viewModel.onClickNextButton()}
 } fun onClickNextButton() { // APIϨεϙϯεͷ݁ՌʹΑͬͯɺը໘ભҠΛม͍͑ͨ৔߹ val data = repository.fetchData() // লུ _nextLiveData.value = nextType } Fragment ViewModel όοΫͰ໭͖ͬͯͨͱ͖ʹɺ onViewCreated͕ݺ͹Εͯɺ observe͍ͯ͠ΔonChanged͕ݺ͹ΕΔͨΊ
69. LiveDataͷϥούʔΫϥεΛ࡞Δ https://medium.com/androiddevelopers/livedata-with-snackbar-navigation-and-other-events-the-singleliveevent-case-ac2622673150 data class Event<out T>(private val content: T) { var hasBeenHandled = false private set fun getContentIfNotHandled(): T? { return if (hasBeenHandled) { null } else { hasBeenHandled = true content } } }
70. LiveDataͷϥούʔΫϥε(Event)Λ࢖͏ override fun onViewCreated() { viewModel.nextLiveData .observe(viewLifecycleOwner) { event -> event.getContentIfNotHandled()?.let {nextViewType -> // ը໘ભҠ͢Δ
 } } button .setOnClickListener{viewModel.onClickNextButton()}
 } fun onClickNextButton() { // APIϨεϙϯεͷ݁ՌʹΑͬͯɺը໘ભҠΛม͍͑ͨ৔߹ val data = repository.fetchData() // লུ _nextLiveData.value = Event(nextType) } Fragment ViewModel
71. LiveDataͷϥούʔΫϥε(Event)Λ࢖͏ override fun onViewCreated() { viewModel.nextLiveData .observe(viewLifecycleOwner) { event -> event.getContentIfNotHandled()?.let {nextViewType -> // ը໘ભҠ͢Δ
 } } button .setOnClickListener{viewModel.onClickNextButton()}
 } fun onClickNextButton() { // APIϨεϙϯεͷ݁ՌʹΑͬͯɺը໘ભҠΛม͍͑ͨ৔߹ val data = repository.fetchData() // লུ _nextLiveData.value = Event(nextType) } Fragment ViewModel EventΛηοτ͢ΔΑ͏ʹมߋ
72. LiveDataͷϥούʔΫϥε(Event)Λ࢖͏ override fun onViewCreated() { viewModel.nextLiveData .observe(viewLifecycleOwner) { event -> event.getContentIfNotHandled()?.let {nextViewType -> // ը໘ભҠ͢Δ
 } } button .setOnClickListener{viewModel.onClickNextButton()}
 } fun onClickNextButton() { // APIϨεϙϯεͷ݁ՌʹΑͬͯɺը໘ભҠΛม͍͑ͨ৔߹ val data = repository.fetchData() // লུ _nextLiveData.value = Event(nextType) } Fragment ViewModel getContentIfNotHandled()ͷ࢓૊ΈͰɺ όοΫͰ໭͖ͬͯͨͱ͖͸null͕ฦΔ ͨΊɺը໘ભҠ͠ͳ͘ͳΓɺ ݩͷը໘ʹ໭Δ͜ͱ͕Ͱ͖Δ EventΛηοτ͢ΔΑ͏ʹมߋ
73. ಈ͔͢
74. ಈ͔͢
75. • Activity΍Fragment͕ը໘ճసͳͲͰ࠶ੜ੒͞Εͯ΋อ͓͖࣋ͯͨ͠ ͍৘ใΛViewModelʹอ࣋͢Δͱ޾ͤʹͳΔ • ViewModelͰܭࢉͨ͠Γอ࣋ͨ͠σʔλͰUIΛߋ৽͢Δʹ͸ɺ LiveDataΛ࢖ͬͯUIʹ௨஌͢Δɻ • AACͷLifecycle͸Activity΍FragmentͷϥΠϑαΠΫϧͰॳظԽ΍ഁغ Λ͍ͯͨ͠ίϯϙʔωϯτΛɺผΫϥεʹ੾Γग़ͤͯεοΩϦͰ͖Δ • ViewModelΛڞ༗͢Δ͜ͱͰɺFragment−ActivityؒΛָʹڞ༗Ͱ͖Δ • ը໘ભҠͰLiveDataΛ࢖͏ͱ͖͸ɺϥούʔΫϥεΛ࡞͓ͬͯ͘ඞཁ ͕͋Γͦ͏ ·ͱΊ
76. • ΋ͬͱৄ͍͠࢓૊ΈΛϒϩάʹ·ͱΊͯ·͢ͷͰɺ͝ ڵຯ͕͋Δํ͸ݟͯΈ͍ͯͩ͘͞ɻ ࠷ޙʹ https://kwmt27.net/2019/09/19/android-lifecycle-codelab/