안드로이드 UI 상태 저장 권장사항

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1. 안드로이드 UI 상태 저장 권장사항 GwangMoo You GDG Songdo Organizer GDG TUK Lead
2. 상상하는 것을 소프트웨어로 구현하는 것을 좋아하는 팡무 GDG Songdo Organizer GDSC TUK Lead 전 아우토크립트 안드로이드 개발 팀장 Who Am I? Section 00 @kisa002 @kisa002 @holykisa
3. Section 00
4. 상태 저장을 아시나요?
5. Section 00 UI 상태 데이터 사용자 입력 데이터 화면 상태 진행도 …. 백그라운드 상태 리사이즈 예외 케이스 화면 회전 테마 변경 시스템 리소스 부족
6. Section 00 By UI UX Expert
7. Section 00 By UI UX Expert
8. 앱에서의 상태 손실 상태 저장 모범 사례 고급 사용 사례 Section 00
9. 고급 사용 사례 개인적인 팁 모음 요약 정리 Section 00
10. 앱에서의 상태 손실 Section 01
11. Section 01 구성요소 변경 화면 회전
12. Section 01 구성요소 변경 테마 변경
13. Section 01 구성요소 변경 • 앱 디스플레이 크기 • 화면 방향 • 글꼴 크기 및 두께 • 언어 • 다크 테마 / 라이트 테마 • 키보드 사용 가능 여부 • And then more… bit.ly/runtime changes
14. Section 01 구성요소 변경 시스템 리소스 필요한 경우 메모리 부족 백그라운드 다른 앱 사용
15. Section 01 성요소 변경 시스템 리소스 필요한 경우 예기치 않은 종료
16. 상태 저장을 위한 모범 사례 Section 02
17. Section 02 구성요소 변경 시스템 리소스 필요한 경우 예기치 않은 종료
18. Section 02 구성요소 변경
19. Section 02 구성요소 변경 ViewModel
20. Section 02 ViewModel 메모리 저장 제한된 메모리 구성 변경에서의 생존 백스택 있는 내비게이션 캐시 UI 상태 빠른 읽고 쓰기
21. sealed class ProfileUIState { object Loading : ProfileUIState() data class Error(val throwable: Throwable? = null) : ProfileUIState() data class Success(val profile: Profile) : ProfileUIState() }
22. class ProfileViewModel(userRepository: UserRepository) : ViewModel() { val uiState = flow { emit(ProfileUIState.Success(userRepository.fetchProfile())) }.catch { ProfileUIState.Error(it) }.stateIn( scope = viewModelScope, started = SharingStarted.WhileSubscribed(5_000), initialValue = ProfileUIState.Loading ) }
23. class ProfileViewModel(userRepository: UserRepository) : ViewModel() { val uiState = flow { emit(ProfileUIState.Success(userRepository.fetchProfile())) }.catch { ProfileUIState.Error(it) }.stateIn( scope = viewModelScope, started = SharingStarted.WhileSubscribed(5_000), initialValue = ProfileUIState.Loading ) }
24. class ProfileViewModel(userRepository: UserRepository) : ViewModel() { val uiState = flow { emit(ProfileUIState.Success(userRepository.fetchProfile())) }.catch { ProfileUIState.Error(it) }.stateIn( scope = viewModelScope, started = SharingStarted.WhileSubscribed(5_000), initialValue = ProfileUIState.Loading ) }
25. class ProfileViewModel(userRepository: UserRepository) : ViewModel() { val uiState = flow { emit(ProfileUIState.Success(userRepository.fetchProfile())) }.catch { ProfileUIState.Error(it) }.stateIn( scope = viewModelScope, started = SharingStarted.WhileSubscribed(5_000), initialValue = ProfileUIState.Loading ) }
26. Section 02 예기치 않은 종료
27. Section 02 예기치 않은 종료 영구 저장
28. Section 02 영구 저장 소규모 단순 데이터 적합 소규모 단순 데이터 적합 비동기 처리 SharedPreferences DataStore 복잡한 데이터 처리 참조 무결성 Room
29. Section 02 영구 저장 디스크 저장 제한된 디스크 공간 구성 변경, 시스템 리소스 부족, 예외 케이스에서의 생존 느린 읽고 쓰기 애플리케이션 데이터
30. Section 02 상태 저장 API 시스템 리소스 필요한 경우
31. Section 02 상태 저장 API 메모리 저장 제한된 번들 구성 변경, 시스템 리소스 부족 생존 느린 읽고 쓰기 큰 정보와 리스트 내비게이션, 사용자 입력에 의존하는 일시적인 상태
32. Section 02 상태 저장 API 느린 읽고 쓰기 큰 정보와 리스트 내비게이션, 사용자 입력에 의존하는 일시적인 상태 리스트의 스크롤 위치 상세화면의 아이템 ID 사용자 설정 진행 상태
33. Section 02 상태 저장 API Jetpack Compose rememberSaveable View System onSaveInstanceState
34. @Composable private fun FaqItem(title: String, content: String) { var visibleContent by remember { mutableStateOf(false) } Column { FaqItemTitle( title = title, visibleContent = visibleContent, onChangeVisibleRequest = { visibleContent = it } ) FaqItemContent( content = content, visibleContent = visibleContent ) Divider() } }
35. @Composable private fun FaqItem(title: String, content: String) { var visibleContent by rememberSaveable { mutableStateOf(false) } Column { FaqItemTitle( title = title, visibleContent = visibleContent, onChangeVisibleRequest = { visibleContent = it } ) FaqItemContent( content = content, visibleContent = visibleContent ) Divider() } }
36. class FaqItemView @JvmOverloads constructor(context: Context, ...) : View(context, ...) { private var isExpanded = false override fun onSaveInstanceState(): Parcelable { super.onSaveInstanceState() return bundleOf(IS_EXPANDED to isExpanded) } override fun onRestoreInstanceState(state: Parcelable) { if (state is Bundle) { isExpanded = state.getBoolean(IS_EXPANDED) } super.onRestoreInstanceState(state) } companion object { private const val IS_EXPANDED = "is_expanded" } } View의 ID 지정되야함
37. Section 02 상태 저장 API 테스트 Jetpack Compose StateRestorationTester View System ActivityScenario.recreate
38. class FaqItemTests { @get:Rule val composeTestRule = createComposeRule() @Test fun onRecreation_stateIsRestored() { val restorationTester = StateRestorationTester(composeTestRule) val (title, content) = "This is title" to "This is content" restorationTester.setContent { FaqItem(title = title, content = content) } composeTestRule.onNodeWithText(title).performClick() composeTestRule.onNodeWithText(content).assertIsDisplayed() restorationTester.emulateSavedInstanceStateRestore() composeTestRule.onNodeWithText(content).assertIsDisplayed() } }
39. Section 02 상태 저장 API UI 로직 Jetpack Compose rememberSaveable View System onSaveInstanceState
40. Section 02 상태 저장 API 비즈니스 로직 ViewModel intergration SavedStateHandle
41. class KeywordViewModel( private val savedStateHandle: SavedStateHandle ) : ViewModel() { var keyword by savedStateHandle.saveable(stateSaver = TextFieldValue.Saver) { mutableStateOf(TextFieldValue("")) } private set fun updateKeyword(newKeyword: TextFieldValue) { keyword = newKeyword } } SavedStateHandle은 액티비티가 Stop 될 때 저장됨
42. Section 02 Jetpack Compose View System UI 로직 rememberSaveable onSaveInstanceState 비즈니스 로직 SavedStateHandle SavedStateHandle
43. 고급 사용 사례 Section 03
44. Section 03 커스텀 UI 상태 저장
45. @Stable class SearchKeywordState( private val articleRepository: ArticleRepository, initialKeyword: String, ) { var keyword by mutableStateOf(TextFieldValue(initialKeyword)) private set }
46. @Composable fun rememberSearchKeywordState( articleRepository: ArticleRepository, initialKeyword: String = "" ) = rememberSaveable( articleRepository, initialKeyword, saver = // TODO: Custom Saver ) { SearchKeywordState(articleRepository, initialKeyword) }
47. @Composable fun rememberSearchKeywordState( articleRepository: ArticleRepository, initialKeyword: String = "" ) = rememberSaveable( articleRepository, initialKeyword, saver = // TODO: Custom Saver ) { SearchKeywordState(articleRepository, initialKeyword) }
48. @Composable fun rememberSearchKeywordState( articleRepository: ArticleRepository, initialKeyword: String = "" ) = rememberSaveable( articleRepository, initialKeyword, saver = // TODO: Custom Saver ) { SearchKeywordState(articleRepository, initialKeyword) }
49. @Stable class SearchKeywordState( private val articleRepository: ArticleRepository, initialKeyword: String ) { var keyword by mutableStateOf(TextFieldValue(initialKeyword)) private set }
50. @Stable class SearchKeywordState( private val articleRepository: ArticleRepository, initialKeyword: String ) { var keyword by mutableStateOf(TextFieldValue(initialKeyword)) private set companion object { fun saver(articleRepository: ArticleRepository): Saver<SearchKeywordState, *> = Saver( save = { it.keyword.text }, restore = { keyword -> SearchKeywordState(articleRepository, keyword) } ) } }
51. @Stable class SearchKeywordState( private val articleRepository: ArticleRepository, initialKeyword: String ) { var keyword by mutableStateOf(TextFieldValue(initialKeyword)) private set companion object { fun saver(articleRepository: ArticleRepository): Saver<SearchKeywordState, *> = Saver( save = { it.keyword.text }, restore = { keyword -> SearchKeywordState(articleRepository, keyword) } ) } }
52. @Stable class SearchKeywordState( private val articleRepository: ArticleRepository, initialKeyword: String ) { var keyword by mutableStateOf(TextFieldValue(initialKeyword)) private set companion object { fun saver(articleRepository: ArticleRepository): Saver<SearchKeywordState, *> = Saver( save = { it.keyword.text }, restore = { keyword -> SearchKeywordState(articleRepository, keyword) } ) } }
53. @Stable class SearchKeywordState( private val articleRepository: ArticleRepository, initialKeyword: String ) { var keyword by mutableStateOf(TextFieldValue(initialKeyword)) private set companion object { fun saver(articleRepository: ArticleRepository): Saver<SearchKeywordState, *> = Saver( save = { it.keyword.text }, restore = { keyword -> SearchKeywordState(articleRepository, keyword) } ) } }
54. @Stable class SearchKeywordState( private val articleRepository: ArticleRepository, initialKeyword: String ) { var keyword by mutableStateOf(TextFieldValue(initialKeyword)) private set companion object { fun saver(articleRepository: ArticleRepository): Saver<SearchKeywordState, *> = Saver( save = { it.keyword.text }, restore = { keyword -> SearchKeywordState(articleRepository, keyword) } ) } }
55. @Composable fun rememberSearchKeywordState( articleRepository: ArticleRepository, initialKeyword: String = "" ) = rememberSaveable( articleRepository, initialKeyword, saver = SearchKeywordState.saver(articleRepository) ) { SearchKeywordState(articleRepository, initialKeyword) }
56. Section 03 View System
57. class SearchKeywordState( private val articleRepository: ArticleRepository, private val initialKeyword: String ) { var keyword = initialKeyword private set }
58. class SearchKeywordState( private val articleRepository: ArticleRepository, private val initialKeyword: String ) : SavedStateRegistry.SavedStateProvider { var keyword = initialKeyword private set }
59. class SearchKeywordState( private val articleRepository: ArticleRepository, private val initialKeyword: String ) : SavedStateRegistry.SavedStateProvider { var keyword = initialKeyword private set override fun saveState(): Bundle = bundleOf(KEYWORD to keyword) companion object { private const val KEYWORD = "keyword" private const val PROVIDER = "search_keyword_state" } }
60. class SearchKeywordState( private val articleRepository: ArticleRepository, private val initialKeyword: String, private val registryOwner: SavedStateRegistryOwner ) : SavedStateRegistry.SavedStateProvider { var keyword = initialKeyword private set init { } }
61. class SearchKeywordState( private val articleRepository: ArticleRepository, private val initialKeyword: String, private val registryOwner: SavedStateRegistryOwner ) : SavedStateRegistry.SavedStateProvider { var keyword = initialKeyword private set init { registryOwner.lifecycle.addObserver(LifecycleEventObserver { _, event -> if (event == Lifecycle.Event.ON_CREATE) { val registry = registryOwner.savedStateRegistry if (registry.getSavedStateProvider(PROVIDER) == null) { registry.registerSavedStateProvider(PROVIDER, this) } val savedState = registry.consumeRestoredStateForKey(PROVIDER) keyword = savedState?.getString(KEYWORD) ?: initialKeyword } }) } }
62. class SearchKeywordState( private val articleRepository: ArticleRepository, private val initialKeyword: String, private val registryOwner: SavedStateRegistryOwner ) : SavedStateRegistry.SavedStateProvider { var keyword = initialKeyword private set init { registryOwner.lifecycle.addObserver(LifecycleEventObserver { _, event -> if (event == Lifecycle.Event.ON_CREATE) { val registry = registryOwner.savedStateRegistry if (registry.getSavedStateProvider(PROVIDER) == null) { registry.registerSavedStateProvider(PROVIDER, this) } val savedState = registry.consumeRestoredStateForKey(PROVIDER) keyword = savedState?.getString(KEYWORD) ?: initialKeyword } }) } }
63. class SearchKeywordState( private val articleRepository: ArticleRepository, private val initialKeyword: String, private val registryOwner: SavedStateRegistryOwner ) : SavedStateRegistry.SavedStateProvider { var keyword = initialKeyword private set init { registryOwner.lifecycle.addObserver(LifecycleEventObserver { _, event -> if (event == Lifecycle.Event.ON_CREATE) { val registry = registryOwner.savedStateRegistry if (registry.getSavedStateProvider(PROVIDER) == null) { registry.registerSavedStateProvider(PROVIDER, this) } val savedState = registry.consumeRestoredStateForKey(PROVIDER) keyword = savedState?.getString(KEYWORD) ?: initialKeyword } }) } }
64. class SearchKeywordState( private val articleRepository: ArticleRepository, private val initialKeyword: String, private val registryOwner: SavedStateRegistryOwner ) : SavedStateRegistry.SavedStateProvider { var keyword = initialKeyword private set init { registryOwner.lifecycle.addObserver(LifecycleEventObserver { _, event -> if (event == Lifecycle.Event.ON_CREATE) { val registry = registryOwner.savedStateRegistry if (registry.getSavedStateProvider(PROVIDER) == null) { registry.registerSavedStateProvider(PROVIDER, this) } val savedState = registry.consumeRestoredStateForKey(PROVIDER) keyword = savedState?.getString(KEYWORD) ?: initialKeyword } }) } }
65. class SearchKeywordState( private val articleRepository: ArticleRepository, private val initialKeyword: String, private val registryOwner: SavedStateRegistryOwner ) : SavedStateRegistry.SavedStateProvider { var keyword = initialKeyword private set init { registryOwner.lifecycle.addObserver(LifecycleEventObserver { _, event -> if (event == Lifecycle.Event.ON_CREATE) { val registry = registryOwner.savedStateRegistry if (registry.getSavedStateProvider(PROVIDER) == null) { registry.registerSavedStateProvider(PROVIDER, this) } val savedState = registry.consumeRestoredStateForKey(PROVIDER) keyword = savedState?.getString(KEYWORD) ?: initialKeyword } }) } }
66. Section 04 개인적인 팁 모음
67. Section 04 커스텀 UI 상태 저장 응용하기
68. Section 04 커스텀 UI 상태 저장 응용하기
69. @Stable class SearchKeywordState( private val articleRepository: ArticleRepository, initialKeyword: String ) { var keyword by mutableStateOf(TextFieldValue(initialKeyword)) private set companion object { fun saver(articleRepository: ArticleRepository): Saver<SearchKeywordState, *> = Saver( save = { it.keyword.text }, restore = { keyword -> SearchKeywordState(articleRepository, keyword) } ) } }
70. @Stable class SearchKeywordState( private val articleRepository: ArticleRepository, initialKeyword: String ) { var keyword by mutableStateOf(TextFieldValue(initialKeyword)) private set companion object { fun saver(articleRepository: ArticleRepository): Saver<SearchKeywordState, *> = Saver( save = { it.keyword.text }, restore = { keyword -> SearchKeywordState(articleRepository, keyword) } ) } }
71. @Stable class SearchKeywordState( coroutineScope: CoroutineScope, private val articleRepository: ArticleRepository, initialKeyword: String ) { var keyword by mutableStateOf(TextFieldValue(initialKeyword)) private set companion object { fun saver(articleRepository: ArticleRepository): Saver<SearchKeywordState, *> = Saver( save = { it.keyword.text }, restore = { keyword -> SearchKeywordState(articleRepository, keyword) } ) } }
72. @Stable class SearchKeywordState( coroutineScope: CoroutineScope, private val articleRepository: ArticleRepository, initialKeyword: String ) { var keyword by mutableStateOf(TextFieldValue(initialKeyword)) private set companion object { fun saver(coroutineScope: CoroutineScope, articleRepository: ArticleRepository): Saver<SearchKeywordState, *> = Saver( save = { it.keyword.text }, restore = { keyword -> SearchKeywordState(coroutineScope, articleRepository, keyword) } ) } }
73. @Stable class SearchKeywordState( coroutineScope: CoroutineScope, private val articleRepository: ArticleRepository, initialKeyword: String ) { val autoCompleteKeywords = snapshotFlow { keyword.text } .transformLatest { if (it.isEmpty()) emit(emptyList()) else { delay(700) emit(articleRepository.fetchAutoCompleteKeywords(it)) } } .stateIn( scope = coroutineScope, started = SharingStarted.Lazily, initialValue = emptyList() ) }
74. @Stable class SearchKeywordState( coroutineScope: CoroutineScope, private val articleRepository: ArticleRepository, initialKeyword: String ) { val autoCompleteKeywords = snapshotFlow { keyword.text } .transformLatest { if (it.isEmpty()) emit(emptyList()) else { delay(700) emit(articleRepository.fetchAutoCompleteKeywords(it)) } } .stateIn( scope = coroutineScope, started = SharingStarted.Lazily, initialValue = emptyList() ) }
75. @Stable class SearchKeywordState( coroutineScope: CoroutineScope, private val articleRepository: ArticleRepository, initialKeyword: String ) { val autoCompleteKeywords = snapshotFlow { keyword.text } .transformLatest { if (it.isEmpty()) emit(emptyList()) else { delay(700) emit(articleRepository.fetchAutoCompleteKeywords(it)) } } .stateIn( scope = coroutineScope, started = SharingStarted.Lazily, initialValue = emptyList() ) }
76. @Stable class SearchKeywordState( coroutineScope: CoroutineScope, private val articleRepository: ArticleRepository, initialKeyword: String ) { val autoCompleteKeywords = snapshotFlow { keyword.text } .transformLatest { if (it.isEmpty()) emit(emptyList()) else { delay(700) emit(articleRepository.fetchAutoCompleteKeywords(it)) } } .stateIn( scope = coroutineScope, started = SharingStarted.Lazily, initialValue = emptyList() ) }
77. @Stable class SearchKeywordState( coroutineScope: CoroutineScope, private val articleRepository: ArticleRepository, initialKeyword: String ) { fun updateKeyword(newKeyword: TextFieldValue) { keyword = newKeyword } fun clearKeyword() { keyword = TextFieldValue("") } }
78. @Composable fun rememberSearchKeywordState( articleRepository: ArticleRepository, initialKeyword: String = "" ) = rememberSaveable( articleRepository, initialKeyword, saver = SearchKeywordState.saver(articleRepository) ) { SearchKeywordState(articleRepository, initialKeyword) }
79. @Composable fun rememberSearchKeywordState( coroutineScope: CoroutineScope = rememberCoroutineScope(), articleRepository: ArticleRepository, initialKeyword: String = "" ) = rememberSaveable( articleRepository, initialKeyword, saver = SearchKeywordState.saver(articleRepository) ) { SearchKeywordState(articleRepository, initialKeyword) }
80. @Composable fun rememberSearchKeywordState( coroutineScope: CoroutineScope = rememberCoroutineScope(), articleRepository: ArticleRepository, initialKeyword: String = "" ) = rememberSaveable( articleRepository, initialKeyword, saver = SearchKeywordState.saver(coroutineScope, articleRepository) ) { SearchKeywordState(coroutineScope, articleRepository, initialKeyword) }
81. @Composable fun KeywordScreen(articleRepository: ArticleRepository) { val keywordSearchState = rememberSearchKeywordState(articleRepository = articleRepository) val autoCompleteKeywords by searchKeywordState.autoCompleteKeywords.collectAsState() Column { TextField( value = searchKeywordState.keyword, onValueChange = searchKeywordState::updateKeyword, trailingIcon = { IconButton(onClick = searchKeywordState::clearKeyword) { ... } } ... ) LazyColumn { items(autoCompleteKeywords) { keyword -> Text(text = keyword, ...) } } } }
82. @Composable fun KeywordScreen(articleRepository: ArticleRepository) { val keywordSearchState = rememberSearchKeywordState(articleRepository = articleRepository) val autoCompleteKeywords by searchKeywordState.autoCompleteKeywords.collectAsState() Column { TextField( value = searchKeywordState.keyword, onValueChange = searchKeywordState::updateKeyword, trailingIcon = { IconButton(onClick = searchKeywordState::clearKeyword) { ... } } ... ) LazyColumn { items(autoCompleteKeywords) { keyword -> Text(text = keyword, ...) } } } }
83. @Composable fun KeywordScreen(articleRepository: ArticleRepository) { val keywordSearchState = rememberSearchKeywordState(articleRepository = articleRepository) val autoCompleteKeywords by searchKeywordState.autoCompleteKeywords.collectAsState() Column { TextField( value = searchKeywordState.keyword, onValueChange = searchKeywordState::updateKeyword, trailingIcon = { IconButton(onClick = searchKeywordState::clearKeyword) { ... } } ... ) LazyColumn { items(autoCompleteKeywords) { keyword -> Text(text = keyword, ...) } } } }
84. @Composable fun KeywordScreen(articleRepository: ArticleRepository) { val keywordSearchState = rememberSearchKeywordState(articleRepository = articleRepository) val autoCompleteKeywords by searchKeywordState.autoCompleteKeywords.collectAsState() Column { TextField( value = searchKeywordState.keyword, onValueChange = searchKeywordState::updateKeyword, trailingIcon = { IconButton(onClick = searchKeywordState::clearKeyword) { ... } } ... ) LazyColumn { items(autoCompleteKeywords) { keyword -> Text(text = keyword, ...) } } } }
85. @Composable fun KeywordScreen(articleRepository: ArticleRepository) { val keywordSearchState = rememberSearchKeywordState(articleRepository = articleRepository) val autoCompleteKeywords by searchKeywordState.autoCompleteKeywords.collectAsState() Column { TextField( value = searchKeywordState.keyword, onValueChange = searchKeywordState::updateKeyword, trailingIcon = { IconButton(onClick = searchKeywordState::clearKeyword) { ... } } ... ) LazyColumn { items(autoCompleteKeywords) { keyword -> Text(text = keyword, ...) } } } }
86. @Composable fun KeywordScreen(articleRepository: ArticleRepository) { val keywordSearchState = rememberSearchKeywordState(articleRepository = articleRepository) val autoCompleteKeywords by searchKeywordState.autoCompleteKeywords.collectAsState() Column { TextField( value = searchKeywordState.keyword, onValueChange = searchKeywordState::updateKeyword, trailingIcon = { IconButton(onClick = searchKeywordState::clearKeyword) { ... } } ... ) LazyColumn { items(autoCompleteKeywords) { keyword -> Text(text = keyword, ...) } } } }
87. @Composable fun KeywordScreen(articleRepository: ArticleRepository) { val keywordSearchState = rememberSearchKeywordState(articleRepository = articleRepository) val autoCompleteKeywords by searchKeywordState.autoCompleteKeywords.collectAsState() Column { TextField( value = searchKeywordState.keyword, onValueChange = searchKeywordState::updateKeyword, trailingIcon = { IconButton(onClick = searchKeywordState::clearKeyword) { ... } } ... ) LazyColumn { items(autoCompleteKeywords) { keyword -> Text(text = keyword, ...) } } } }
88. @Composable fun KeywordScreen(articleRepository: ArticleRepository) { val keywordSearchState = rememberSearchKeywordState(articleRepository = articleRepository) val autoCompleteKeywords by searchKeywordState.autoCompleteKeywords.collectAsState() Column { TextField( value = searchKeywordState.keyword, onValueChange = searchKeywordState::updateKeyword, trailingIcon = { IconButton(onClick = searchKeywordState::clearKeyword) { ... } } ... ) LazyColumn { items(autoCompleteKeywords) { keyword -> Text(text = keyword, ...) } } } }
89. Section 04 실제로도 이렇게 쓰나요?
90. Section 04 Now in Android 에서도 기본 앱 상태로 사용하고 있음
91. @Stable class NiaAppState( val navController: NavHostController, val coroutineScope: CoroutineScope, networkMonitor: NetworkMonitor, userNewsResourceRepository: UserNewsResourceRepository, ) { val topLevelDestinationsWithUnreadResources: StateFlow<Set<TopLevelDestination>> = userNewsResourceRepository.observeAllForFollowedTopics() .combine(userNewsResourceRepository.observeAllBookmarked()) { forYouNewsResources, bookmarkedNewsResources -> setOfNotNull( FOR_YOU.takeIf { forYouNewsResources.any { !it.hasBeenViewed } }, BOOKMARKS.takeIf { bookmarkedNewsResources.any { !it.hasBeenViewed } }, ) }.stateIn( coroutineScope, SharingStarted.WhileSubscribed(5_000), initialValue = emptySet(), ) // More code... }
92. Section 04 영구 저장 응용하기
93. Section 04 영구 저장 응용하기
94. class ArticleWriteViewModel( private val articleRepository: ArticleRepository ) : ViewModel() { /* ... */ fun saveDraftArticle() { viewModelScope.launch { articleRepository.saveDraftArticle(title.value, content.value) } } }
95. // Activity override fun onStop() { super.onStop() viewModel.saveDraftArticle() } 실제 구현 시에는 업로드 성공 후 저장하지 않도록 개편 필요
96. Section 04 영구 저장 응용하기 Exception 및 강제 종료에는 저장 ❌
97. private val _title = MutableStateFlow("") private val _content = MutableStateFlow("") val title = _title.asStateFlow() val content = _content.asStateFlow() init { viewModelScope.launch { title.combine(content) { title, content -> title to content } .debounce(5_000) .collect { (title, content) -> articleRepository.saveDraftArticle(title, content) } } }
98. private val _title = MutableStateFlow("") private val _content = MutableStateFlow("") val title = _title.asStateFlow() val content = _content.asStateFlow() init { viewModelScope.launch { title.combine(content) { title, content -> title to content } .debounce(5_000) .collect { (title, content) -> articleRepository.saveDraftArticle(title, content) } } }
99. private val _title = MutableStateFlow("") private val _content = MutableStateFlow("") val title = _title.asStateFlow() val content = _content.asStateFlow() init { viewModelScope.launch { title.combine(content) { title, content -> title to content } .debounce(5_000) .collect { (title, content) -> articleRepository.saveDraftArticle(title, content) } } }
100. private val _title = MutableStateFlow("") private val _content = MutableStateFlow("") val title = _title.asStateFlow() val content = _content.asStateFlow() init { viewModelScope.launch { title.combine(content) { title, content -> title to content } .debounce(5_000) .collect { (title, content) -> articleRepository.saveDraftArticle(title, content) } } }
101. private val _title = MutableStateFlow("") private val _content = MutableStateFlow("") val title = _title.asStateFlow() val content = _content.asStateFlow() init { viewModelScope.launch { title.combine(content) { title, content -> title to content } .debounce(5_000) .collect { (title, content) -> articleRepository.saveDraftArticle(title, content) } } }
102. Section 04 영구 저장 응용하기 Exception 및 강제 종료에도 생존 ✅
103. Section 04 시스템 리소스 필요한 경우 연출하기
104. Section 04
105. Section 04
106. Section 04 활성화되어 있는 경우 ActivityScenario 테스트 시 오류 발생
107. Section 04 메모리에서 제거될 가능성
108. Section 04
109. Section 04
110. Section 04 종료될 확률 프로세스 상태 최종 액티비티 상태 매우 낮음 포그라운드 포커스를 갖거나 갖을 예정 재개됨 낮음 보임 포커스 없음 시작됨/일시정지됨 높음 백그라운드 보이지 않음 중지됨 매우 높음 비어있음 소멸됨 bit.ly/docs activity lifecycle
111. Section 05 요약 정리
112. Section 05 구성요소 변경 시스템 리소스 필요한 경우 예기치 않은 종료
113. 구성 변경 메모리 UI 상태 시스템 리소스 필요한 경우 번들 사용자 입력, 내비게이션 의존하는 일시적인 UI 상태 예상치 못한 앱 종료 디스크 애플리케이션 데이터 생존 공간 용도 ViewModel 상태 저장 API 영구 저장
114. Section 05 bit.ly/saving states
115. Thank You GwangMoo You GDG Songdo Organizer GDG TUK Lead GitHub