取消已经开始的活动？

huangapple
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英文:

How do I cancel an event after another one has started?

问题

我遇到一个问题，即在Snackbar出现后，FAB在Snackbar消息的时间段内不执行导航。如果我在Snackbar显示时多次点击它，它会堆叠并打开多个相同屏幕的实例（仅在Snackbar消失后）。如何在点击FAB时取消显示Snackbar并在任何时候保留FAB的功能？

TasksList.kt：

  1. @OptIn(ExperimentalMaterial3Api::class)
  2. @Composable
  3. fun TasksListScreen(
  4.     modifier: Modifier = Modifier,
  5.     onNavigate: (UiEvent.Navigate) -> Unit,
  6.     viewModel: TaskListViewModel = hiltViewModel()
  7. ) {
  8.     val tasks = viewModel.tasks.collectAsState(initial = emptyList())
  9.     val snackbarHostState = remember { SnackbarHostState() }
  10.     LaunchedEffect(key1 = true) {
  11.         viewModel.uiEvent.collect { event ->
  12.             when (event) {
  13.                 is UiEvent.ShowSnackbar -> {
  14.                     val result = snackbarHostState.showSnackbar(
  15.                         message = event.message,
  16.                         actionLabel = event.action,
  17.                         duration = SnackbarDuration.Long,
  18.                     )
  19.                     if (result == SnackbarResult.ActionPerformed) {
  20.                         viewModel.onEvent(TaskListEvent.OnUndoDeleteTask)
  21.                     }
  22.                 }
  23.                 is UiEvent.Navigate -> onNavigate(event)
  24.                 else -> Unit
  25.             }
  26.         }
  27.     }
  28.     Scaffold(
  29.         snackbarHost = {
  30.             SnackbarHost(snackbarHostState) { data ->
  31.                 Snackbar(
  32.                     shape = RoundedShapes.medium,
  33.                     actionColor = MaterialTheme.colorScheme.primary,
  34.                     contentColor = MaterialTheme.colorScheme.background,
  35.                     snackbarData = data
  36.                 )
  37.             }
  38.         },
  39.         floatingActionButton = {
  40.             FloatingActionButton(
  41.                 shape = RoundedShapes.medium,
  42.                 onClick = { viewModel.onEvent(TaskListEvent.OnAddTask) },
  43.                 containerColor = MaterialTheme.colorScheme.primary,
  44.                 contentColor = MaterialTheme.colorScheme.background
  45.             ) {
  46.                 Icon(
  47.                     imageVector = Icons.Default.Add,
  48.                     contentDescription = stringResource(R.string.fab_cd)
  49.                 )
  50.             }
  51.         },
  52.         topBar = {
  53.             TopAppBar(
  54.                 title = { Text(stringResource(R.string.app_name)) },
  55.                 colors = TopAppBarDefaults.topAppBarColors(
  56.                     containerColor = MaterialTheme.colorScheme.primary,
  57.                     titleContentColor = MaterialTheme.colorScheme.background
  58.                 )
  59.             }
  60.         },
  61.     ) { padding ->
  62.         LazyColumn(
  63.             state = rememberLazyListState(),
  64.             verticalArrangement = spacedBy(12.dp),
  65.             contentPadding = PaddingValues(vertical = 16.dp),
  66.             modifier = modifier
  67.                 .fillMaxSize()
  68.                 .padding(padding)
  69.                 .padding(horizontal = 16.dp),
  70.         ) {
  72.             items(items = tasks.value, key = { task -> task.hashCode() }) { task ->
  73.                 val currentTask by rememberUpdatedState(newValue = task)
  74.                 val dismissState = rememberDismissState(confirmValueChange = {
  75.                     if (it == DismissValue.DismissedToStart) {
  76.                         viewModel.onEvent(TaskListEvent.OnDeleteTask(currentTask))
  77.                     }
  78.                     true
  79.                 })
  80.                 SwipeToDismiss(state = dismissState,
  81.                     directions = setOf(DismissDirection.EndToStart),
  82.                     background = { },
  83.                     dismissContent = {
  84.                         TaskItem(
  85.                             task = task, modifier = modifier
  86.                         )
  87.                     })
  88.             }
  89.         }
  90.     }
  91. }

TaskListViewModel：

  1. @HiltViewModel
  2. class TaskListViewModel @Inject constructor(private val repository: TaskRepositoryImplementation) :
  3.     ViewModel() {
  5.     val tasks = repository.getTasks()
  7.     private val _uiEvent = Channel<UiEvent>()
  8.     val uiEvent = _uiEvent.receiveAsFlow()
  10.     private var deletedTask: Task? = null
  12.     fun onEvent(event: TaskListEvent) {
  13.         when (event) {
  14.             is TaskListEvent.OnAddTask -> {
  15.                 sendUiEvent(UiEvent.Navigate(Routes.ADD_EDIT_TASK))
  16.             }
  17.             is TaskListEvent.OnEditClick -> {
  18.                 sendUiEvent(UiEvent.Navigate(Routes.ADD_EDIT_TASK + "?taskId=${event.task.id}"))
  19.             }
  20.             is TaskListEvent.OnDeleteTask -> {
  21.                 val context = TaskApp.instance?.context
  22.                 viewModelScope.launch(Dispatchers.IO) {
  23.                     deletedTask = event.task
  24.                     repository.deleteTask(event.task)
  25.                     if (context != null) {
  26.                         sendUiEvent(
  27.                             UiEvent.ShowSnackbar(
  28.                                 message = context.getString(R.string.snackbar_deleted),
  29.                                 action = context.getString(R.string.snackbar_action)
  30.                             )
  31.                         )
  32.                     }
  33.                 }
  35.             }
  36.             is TaskListEvent.OnUndoDeleteTask -> {
  37.                 deletedTask?.let { task ->
  38.                     viewModelScope.launch {
  39.                         repository.addTask(task)
  40.                     }
  41.                 }
  43.             }
  44.         }
  45.     }
  47.     private fun sendUiEvent(event: UiEvent) {
  48.         viewModelScope.launch(Dispatchers.IO) {
  49.             _uiEvent.send(event)
  50.         }
  51.     }
  53. }
英文:

I am having an issue, where after a Snackbar appears the FAB won't perform navigation for the period of the Snackbar message. If I click it multiple times when the Snackbar is displayed it will stack and open multiple instances of one screen (only after the Snackbar is gone). How do I cancel showing the Snackbar on click of the FAB and preserve the functionality of the FAB at all times?

TasksList.kt:

  1. @OptIn(ExperimentalMaterial3Api::class)
  2. @Composable
  3. fun TasksListScreen(
  4. modifier: Modifier = Modifier,
  5. onNavigate: (UiEvent.Navigate) -&gt; Unit,
  6. viewModel: TaskListViewModel = hiltViewModel()
  7. ) {
  8. val tasks = viewModel.tasks.collectAsState(initial = emptyList())
  9. val snackbarHostState = remember { SnackbarHostState() }
  10. LaunchedEffect(key1 = true) {
  11. viewModel.uiEvent.collect { event -&gt;
  12. when (event) {
  13. is UiEvent.ShowSnackbar -&gt; {
  14. val result = snackbarHostState.showSnackbar(
  15. message = event.message,
  16. actionLabel = event.action,
  17. duration = SnackbarDuration.Long,
  18. )
  19. if (result == SnackbarResult.ActionPerformed) {
  20. viewModel.onEvent(TaskListEvent.OnUndoDeleteTask)
  21. }
  22. }
  23. is UiEvent.Navigate -&gt; onNavigate(event)
  24. else -&gt; Unit
  25. }
  26. }
  27. }
  28. Scaffold(
  29. snackbarHost = {
  30. SnackbarHost(snackbarHostState) { data -&gt;
  31. Snackbar(
  32. shape = RoundedShapes.medium,
  33. actionColor = MaterialTheme.colorScheme.primary,
  34. contentColor = MaterialTheme.colorScheme.background,
  35. snackbarData = data
  36. )
  37. }
  38. },
  39. floatingActionButton = {
  40. FloatingActionButton(
  41. shape = RoundedShapes.medium,
  42. onClick = { viewModel.onEvent(TaskListEvent.OnAddTask) },
  43. containerColor = MaterialTheme.colorScheme.primary,
  44. contentColor = MaterialTheme.colorScheme.background
  45. ) {
  46. Icon(
  47. imageVector = Icons.Default.Add,
  48. contentDescription = stringResource(R.string.fab_cd)
  49. )
  50. }
  51. },
  52. topBar = {
  53. TopAppBar(
  54. title = { Text(stringResource(R.string.app_name)) },
  55. colors = TopAppBarDefaults.topAppBarColors(
  56. containerColor = MaterialTheme.colorScheme.primary,
  57. titleContentColor = MaterialTheme.colorScheme.background
  58. )
  59. )
  60. },
  61. ) { padding -&gt;
  62. LazyColumn(
  63. state = rememberLazyListState(),
  64. verticalArrangement = spacedBy(12.dp),
  65. contentPadding = PaddingValues(vertical = 16.dp),
  66. modifier = modifier
  67. .fillMaxSize()
  68. .padding(padding)
  69. .padding(horizontal = 16.dp),
  70. ) {
  71. items(items = tasks.value, key = { task -&gt; task.hashCode() }) { task -&gt;
  72. val currentTask by rememberUpdatedState(newValue = task)
  73. val dismissState = rememberDismissState(confirmValueChange = {
  74. if (it == DismissValue.DismissedToStart) {
  75. viewModel.onEvent(TaskListEvent.OnDeleteTask(currentTask))
  76. }
  77. true
  78. })
  79. SwipeToDismiss(state = dismissState,
  80. directions = setOf(DismissDirection.EndToStart),
  81. background = { },
  82. dismissContent = {
  83. TaskItem(
  84. task = task, modifier = modifier
  85. )
  86. })
  87. }
  88. }
  89. }
  90. }

TaskListViewModel:

  1. @HiltViewModel
  2. class TaskListViewModel @Inject constructor(private val repository: TaskRepositoryImplementation) :
  3. ViewModel() {
  4. val tasks = repository.getTasks()
  5. private val _uiEvent = Channel&lt;UiEvent&gt;()
  6. val uiEvent = _uiEvent.receiveAsFlow()
  7. private var deletedTask: Task? = null
  8. fun onEvent(event: TaskListEvent) {
  9. when (event) {
  10. is TaskListEvent.OnAddTask -&gt; {
  11. sendUiEvent(UiEvent.Navigate(Routes.ADD_EDIT_TASK))
  12. }
  13. is TaskListEvent.OnEditClick -&gt; {
  14. sendUiEvent(UiEvent.Navigate(Routes.ADD_EDIT_TASK + &quot;?taskId=${event.task.id}&quot;))
  15. }
  16. is TaskListEvent.OnDeleteTask -&gt; {
  17. val context = TaskApp.instance?.context
  18. viewModelScope.launch(Dispatchers.IO) {
  19. deletedTask = event.task
  20. repository.deleteTask(event.task)
  21. if (context != null) {
  22. sendUiEvent(
  23. UiEvent.ShowSnackbar(
  24. message = context.getString(R.string.snackbar_deleted),
  25. action = context.getString(R.string.snackbar_action)
  26. )
  27. )
  28. }
  29. }
  30. }
  31. is TaskListEvent.OnUndoDeleteTask -&gt; {
  32. deletedTask?.let { task -&gt;
  33. viewModelScope.launch {
  34. repository.addTask(task)
  35. }
  36. }
  37. }
  38. }
  39. }
  40. private fun sendUiEvent(event: UiEvent) {
  41. viewModelScope.launch(Dispatchers.IO) {
  42. _uiEvent.send(event)
  43. }
  44. }
  45. }

答案1

得分: 2

以下是您要的代码的中文翻译：

  1. // 创建SnackbarController类以创建可取消的Snackbar
  3. // 受此存储库启发 [SnackbarController][1]
  5. // 公开方法**cancelActiveJob**以取消可见的Snackbar
  7. class SnackBarController(private val coroutineScope: CoroutineScope) {
  8.     private var snackBarJob: Job? = null
  10.     init {
  11.         cancelActiveJob()
  12.     }
  14.     suspend fun showSnackBar(
  15.         snackBarHostState: SnackbarHostState,
  16.         message: String,
  17.         actionLabel: String? = null,
  18.         duration: SnackbarDuration
  19.     ): SnackbarResult {
  20.         var result: SnackbarResult = SnackbarResult.Dismissed
  21.         if (snackBarJob == null) {
  22.             snackBarJob = coroutineScope.launch {
  23.                 result = snackBarHostState.showSnackbar(
  24.                     message = message,
  25.                     actionLabel = actionLabel,
  26.                     duration = duration
  27.                 )
  28.                 cancelActiveJob()
  29.             }
  30.         } else {
  31.             cancelActiveJob()
  32.             snackBarJob = coroutineScope.launch {
  33.                 result = snackBarHostState.showSnackbar(
  34.                     message = message,
  35.                     actionLabel = actionLabel,
  36.                     duration = duration
  37.                 )
  38.                 cancelActiveJob()
  39.             }
  40.         }
  41.         snackBarJob?.join()
  42.         return result
  43.     }
  45.     fun cancelActiveJob() {
  46.         snackBarJob?.let { job ->
  47.             job.cancel()
  48.             snackBarJob = Job()
  49.         }
  50.     }
  51. }

在TaskListScreen中：

  1. val tasks = viewModel.tasks.collectAsState(initial = emptyList())
  2. val snackbarHostState = remember { SnackbarHostState() }
  3. val coroutineScope = rememberCoroutineScope()
  4. val snackBarController = SnackBarController(coroutineScope)
  6. LaunchedEffect(key1 = true) {
  7.     viewModel.uiEvent.collectLatest { event ->
  8.         when (event) {
  9.             is UiEvent.ShowSnackbar -> {
  10.                 val result = snackBarController.showSnackBar(
  11.                     message = event.message,
  12.                     actionLabel = event.action,
  13.                     duration = SnackbarDuration.Long,
  14.                 )
  15.                 if (result == SnackbarResult.ActionPerformed) {
  16.                     viewModel.onEvent(TaskListEvent.OnUndoDeleteTask)
  17.                 }
  18.             }
  19.             is UiEvent.Navigate -> {
  20.                 // 如果要隐藏Snackbar
  21.                 snackBarController.cancelActiveJob()
  22.                 onNavigate(event)
  23.             }
  24.             else -> Unit
  25.         }
  26.     }
  27. }

注意：如果多次调用snackbarController.showSnackBar()，它会替换当前可见的Snackbar。

  2. <details>
  3. <summary>英文:</summary>
  4. Create this SnackbarController class to create a cancellable snackbar
  5. Inspired by this repo [SnackbarController][1]
  6. Expose the method **cancelActiveJob** to cancel the visible snackbar
  7. class SnackBarController(private val coroutineScope: CoroutineScope) {
  8. private var snackBarJob: Job? = null
  9. init {
  10. cancelActiveJob()
  11. }
  12. suspend fun showSnackBar(
  13. snackBarHostState: SnackbarHostState,
  14. message: String,
  15. actionLabel: String? = null,
  16. duration: SnackbarDuration
  17. ): SnackbarResult {
  18. var result: SnackbarResult = SnackbarResult.Dismissed
  19. if (snackBarJob == null) {
  20. snackBarJob = coroutineScope.launch {
  21. result = snackBarHostState.showSnackbar(
  22. message = message,
  23. actionLabel = actionLabel,
  24. duration = duration
  25. )
  26. cancelActiveJob()
  27. }
  28. } else {
  29. cancelActiveJob()
  30. snackBarJob = coroutineScope.launch {
  31. result = snackBarHostState.showSnackbar(
  32. message = message,
  33. actionLabel = actionLabel,
  34. duration = duration
  35. )
  36. cancelActiveJob()
  37. }
  38. }
  39. snackBarJob?.join()
  40. return result
  41. }
  42. fun cancelActiveJob() {
  43. snackBarJob?.let { job -&gt;
  44. job.cancel()
  45. snackBarJob = Job()
  46. }
  47. }
  48. }
  49. In the TaskListScreen
  50. val tasks = viewModel.tasks.collectAsState(initial = emptyList())
  51. val snackbarHostState = remember { SnackbarHostState() }
  52. val coroutineScope = rememberCoroutineScope()
  53. val snackBarController = SnackBarController(coroutineScope)
  54. LaunchedEffect(key1 = true) {
  55. viewModel.uiEvent.collectLatest{ event -&gt;
  56. when (event) {
  57. is UiEvent.ShowSnackbar -&gt; {
  58. val result = snackBarController.showSnackBar(
  59. message = event.message,
  60. actionLabel = event.action,
  61. duration = SnackbarDuration.Long,
  62. )
  63. if (result == SnackbarResult.ActionPerformed) {
  64. viewModel.onEvent(TaskListEvent.OnUndoDeleteTask)
  65. }
  66. }
  67. is UiEvent.Navigate -&gt; {
  68. //if you want to hide the snackBar
  69. snackBarController.cancelActiveJob()
  70. onNavigate(event)
  71. }
  72. else -&gt; Unit
  73. }
  74. }
  75. }
  76. Note if you call snackbarController.showSnackbar() more than once
  77. It replaces the current visible snackbar
  78. [1]: https://github.com/mitchtabian/food2fork-compose/blob/d291d5114a0a5dd09e7d5ab2de3804607cfbd5d2/app/src/main/java/com/codingwithmitch/food2forkcompose/presentation/components/util/SnackbarController.kt
  79. </details>

huangapple
  • 本文由 发表于 2023年2月18日 02:51:21
  • 转载请务必保留本文链接：https://go.coder-hub.com/75488259.html
  • android
  • android-jetpack-compose
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