Update General Error Handling Implementation

Include OFFLINE message in list of messages, with precedence over other messages. Pass offline value to state for use in other purposes.

Include action handling for success/failure to click snackbar button. Implementation of Bookmark UNDO function.

Moved implementations of onShowSnackbar and errorHandler closer to use case, removed unnecessary passed down parameters.

app/src/androidTest/kotlin/com/google/samples/apps/nowinandroid/ui/NiaAppStateTest.kt

@@ -76,7 +76,6 @@ class NiaAppStateTest {
                 NiaAppState(
                     navController = navController,
                     coroutineScope = backgroundScope,
-                    networkMonitor = networkMonitor,
                     errorMonitor = errorMonitor,
                     userNewsResourceRepository = userNewsResourceRepository,
                     timeZoneMonitor = timeZoneMonitor,
@@ -99,7 +98,6 @@ class NiaAppStateTest {
     fun niaAppState_destinations() = runTest {
         composeTestRule.setContent {
             state = rememberNiaAppState(
-                networkMonitor = networkMonitor,
                 errorMonitor = errorMonitor,
                 userNewsResourceRepository = userNewsResourceRepository,
                 timeZoneMonitor = timeZoneMonitor,
@@ -118,7 +116,6 @@ class NiaAppStateTest {
             state = NiaAppState(
                 navController = NavHostController(LocalContext.current),
                 coroutineScope = backgroundScope,
-                networkMonitor = networkMonitor,
                 errorMonitor = errorMonitor,
                 userNewsResourceRepository = userNewsResourceRepository,
                 timeZoneMonitor = timeZoneMonitor,
@@ -129,7 +126,7 @@ class NiaAppStateTest {
         networkMonitor.setConnected(false)
         assertEquals(
             true,
-            state.isOffline.value,
+            state.isOfflineState.value,
         )
     }
 
@@ -139,7 +136,6 @@ class NiaAppStateTest {
             state = NiaAppState(
                 navController = NavHostController(LocalContext.current),
                 coroutineScope = backgroundScope,
-                networkMonitor = networkMonitor,
                 errorMonitor = errorMonitor,
                 userNewsResourceRepository = userNewsResourceRepository,
                 timeZoneMonitor = timeZoneMonitor,
@@ -160,14 +156,13 @@ class NiaAppStateTest {
             state = NiaAppState(
                 navController = NavHostController(LocalContext.current),
                 coroutineScope = backgroundScope,
-                networkMonitor = networkMonitor,
                 errorMonitor = errorMonitor,
                 userNewsResourceRepository = userNewsResourceRepository,
                 timeZoneMonitor = timeZoneMonitor,
             )
         }
 
-        val id = state.addErrorMessage("Test Error Message 1")
+        val id = state.addShortErrorMessage("Test Error Message 1")
 
         backgroundScope.launch { state.snackbarMessage.collect() }
 

app/src/main/kotlin/com/google/samples/apps/nowinandroid/MainActivity.kt

@@ -136,7 +136,6 @@ class MainActivity : ComponentActivity() {
             }
 
             val appState = rememberNiaAppState(
-                networkMonitor = networkMonitor,
                 errorMonitor = errorMonitor,
                 userNewsResourceRepository = userNewsResourceRepository,
                 timeZoneMonitor = timeZoneMonitor,

app/src/main/kotlin/com/google/samples/apps/nowinandroid/navigation/NiaNavHost.kt

@@ -38,12 +38,11 @@ import com.google.samples.apps.nowinandroid.ui.interests2pane.interestsListDetai
 @Composable
 fun NiaNavHost(
     appState: NiaAppState,
-    onShowSnackbar: suspend (String, String?) -> Boolean,
-    errorHandler: (String) -> Unit,
     modifier: Modifier = Modifier,
     startDestination: String = FOR_YOU_ROUTE,
 ) {
     val navController = appState.navController
+
     NavHost(
         navController = navController,
         startDestination = startDestination,
@@ -52,13 +51,13 @@ fun NiaNavHost(
         forYouScreen(onTopicClick = navController::navigateToInterests)
         bookmarksScreen(
             onTopicClick = navController::navigateToInterests,
-            onShowSnackbar = onShowSnackbar,
+            onShowSnackbar = { message, label, actionSuccess, actionFailure -> appState.addLongErrorMessage(error = message, label = label, successAction = actionSuccess, failureAction = actionFailure) },
         )
         searchScreen(
             onBackClick = navController::popBackStack,
             onInterestsClick = { appState.navigateToTopLevelDestination(INTERESTS) },
             onTopicClick = navController::navigateToInterests,
-            errorHandler = errorHandler,
+            errorHandler = { message -> appState.addShortErrorMessage(message) },
         )
         interestsListDetailScreen()
     }

app/src/main/kotlin/com/google/samples/apps/nowinandroid/ui/NiaApp.kt

@@ -30,6 +30,7 @@ import androidx.compose.material3.ExperimentalMaterial3Api
 import androidx.compose.material3.Icon
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Scaffold
+import androidx.compose.material3.SnackbarDuration
 import androidx.compose.material3.SnackbarDuration.Indefinite
 import androidx.compose.material3.SnackbarDuration.Short
 import androidx.compose.material3.SnackbarHost
@@ -42,6 +43,7 @@ import androidx.compose.material3.adaptive.WindowAdaptiveInfo
 import androidx.compose.material3.adaptive.currentWindowAdaptiveInfo
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.SideEffect
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
@@ -62,6 +64,8 @@ import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import androidx.navigation.NavDestination
 import androidx.navigation.NavDestination.Companion.hierarchy
 import com.google.samples.apps.nowinandroid.R
+import com.google.samples.apps.nowinandroid.core.data.util.ErrorMessage
+import com.google.samples.apps.nowinandroid.core.data.util.MessageDuration
 import com.google.samples.apps.nowinandroid.core.designsystem.component.NiaBackground
 import com.google.samples.apps.nowinandroid.core.designsystem.component.NiaGradientBackground
 import com.google.samples.apps.nowinandroid.core.designsystem.component.NiaNavigationSuiteScaffold
@@ -95,32 +99,26 @@ fun NiaApp(
         ) {
             val snackbarHostState = remember { SnackbarHostState() }
 
-            val isOffline by appState.isOffline.collectAsStateWithLifecycle()
+            val offlineMessage = stringResource(R.string.not_connected)
+            SideEffect {
+                appState.offlineMessage = offlineMessage
+            }
+
             val snackbarMessage by appState.snackbarMessage.collectAsStateWithLifecycle()
 
-            // If user is not connected to the internet show a snack bar to inform them.
-            val notConnectedMessage = stringResource(R.string.not_connected)
-            LaunchedEffect(isOffline) {
-                if (isOffline) {
-                    snackbarHostState.showSnackbar(
-                        message = notConnectedMessage,
-                        duration = Indefinite,
-                    )
-                }
-            }
             LaunchedEffect(snackbarMessage) {
                 snackbarMessage?.let {
                     val snackBarResult = snackbarHostState.showSnackbar(
                         message = it.message,
-                        actionLabel = "Continue",
-                        duration = Indefinite,
+                        actionLabel = it.label,
+                        duration = snackbarDurationOf(it.duration),
                     ) == ActionPerformed
 
-                    if (snackBarResult) {
+                    handleSnackbarResult(snackBarResult, it)
+                    // Remove Message from Queue
                     appState.clearErrorMessage(it.id)
                 }
             }
-            }
 
             NiaApp(
                 appState = appState,
@@ -243,14 +241,6 @@ internal fun NiaApp(
                 ) {
                     NiaNavHost(
                         appState = appState,
-                        onShowSnackbar = { message, action ->
-                            snackbarHostState.showSnackbar(
-                                message = message,
-                                actionLabel = action,
-                                duration = Short,
-                            ) == ActionPerformed
-                        },
-                        errorHandler = { message -> appState.addErrorMessage(message) },
                     )
                 }
 
@@ -284,3 +274,20 @@ private fun NavDestination?.isTopLevelDestinationInHierarchy(destination: TopLev
     this?.hierarchy?.any {
         it.route?.contains(destination.name, true) ?: false
     } ?: false
+
+private fun snackbarDurationOf(duration: MessageDuration?): SnackbarDuration {
+    return when (duration) {
+        MessageDuration.Short -> SnackbarDuration.Short
+        MessageDuration.Long -> SnackbarDuration.Long
+        MessageDuration.Indefinite -> SnackbarDuration.Indefinite
+        else -> SnackbarDuration.Short
+    }
+}
+
+private fun handleSnackbarResult(snackBarResult: Boolean, message: ErrorMessage) {
+    if (snackBarResult) {
+        message.actionPerformed?.invoke()
+    } else {
+        message.actionNotPerformed?.invoke()
+    }
+}

app/src/main/kotlin/com/google/samples/apps/nowinandroid/ui/NiaAppState.kt

@@ -29,8 +29,8 @@ import androidx.navigation.compose.rememberNavController
 import androidx.navigation.navOptions
 import androidx.tracing.trace
 import com.google.samples.apps.nowinandroid.core.data.repository.UserNewsResourceRepository
+import com.google.samples.apps.nowinandroid.core.data.util.ErrorMessage
 import com.google.samples.apps.nowinandroid.core.data.util.ErrorMonitor
-import com.google.samples.apps.nowinandroid.core.data.util.NetworkMonitor
 import com.google.samples.apps.nowinandroid.core.data.util.TimeZoneMonitor
 import com.google.samples.apps.nowinandroid.core.ui.TrackDisposableJank
 import com.google.samples.apps.nowinandroid.feature.bookmarks.navigation.BOOKMARKS_ROUTE
@@ -48,13 +48,11 @@ import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.flow.SharingStarted
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.combine
-import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.stateIn
 import kotlinx.datetime.TimeZone
 
 @Composable
 fun rememberNiaAppState(
-    networkMonitor: NetworkMonitor,
     errorMonitor: ErrorMonitor,
     userNewsResourceRepository: UserNewsResourceRepository,
     timeZoneMonitor: TimeZoneMonitor,
@@ -65,7 +63,6 @@ fun rememberNiaAppState(
     return remember(
         navController,
         coroutineScope,
-        networkMonitor,
         errorMonitor,
         userNewsResourceRepository,
         timeZoneMonitor,
@@ -73,7 +70,6 @@ fun rememberNiaAppState(
         NiaAppState(
             navController = navController,
             coroutineScope = coroutineScope,
-            networkMonitor = networkMonitor,
             errorMonitor = errorMonitor,
             userNewsResourceRepository = userNewsResourceRepository,
             timeZoneMonitor = timeZoneMonitor,
@@ -85,7 +81,6 @@ fun rememberNiaAppState(
 class NiaAppState(
     val navController: NavHostController,
     coroutineScope: CoroutineScope,
-    networkMonitor: NetworkMonitor,
     errorMonitor: ErrorMonitor,
     userNewsResourceRepository: UserNewsResourceRepository,
     timeZoneMonitor: TimeZoneMonitor,
@@ -102,17 +97,13 @@ class NiaAppState(
             else -> null
         }
 
-    val isOffline = networkMonitor.isOnline
-        .map(Boolean::not)
-        .stateIn(
+    val isOfflineState: StateFlow<Boolean> = isOffline.stateIn(
         scope = coroutineScope,
         started = SharingStarted.WhileSubscribed(5_000),
         initialValue = false,
     )
 
-    val snackbarMessage = errorMessages
-        .map { it.firstOrNull() }
-        .stateIn(
+    val snackbarMessage: StateFlow<ErrorMessage?> = errorMessage.stateIn(
         scope = coroutineScope,
         started = SharingStarted.WhileSubscribed(5_000),
         initialValue = null,

app/src/testDemo/kotlin/com/google/samples/apps/nowinandroid/ui/NiaAppScreenSizesScreenshotTests.kt

@@ -138,7 +138,6 @@ class NiaAppScreenSizesScreenshotTests {
                 ) {
                     NiaTheme {
                         val fakeAppState = rememberNiaAppState(
-                            networkMonitor = networkMonitor,
                             errorMonitor = errorMonitor,
                             userNewsResourceRepository = userNewsResourceRepository,
                             timeZoneMonitor = timeZoneMonitor,

app/src/testDemo/kotlin/com/google/samples/apps/nowinandroid/ui/SnackbarScreenshotTests.kt

@@ -218,7 +218,6 @@ class SnackbarScreenshotTests {
                     BoxWithConstraints {
                         NiaTheme {
                             val appState = rememberNiaAppState(
-                                networkMonitor = networkMonitor,
                                 errorMonitor = errorMonitor,
                                 userNewsResourceRepository = userNewsResourceRepository,
                                 timeZoneMonitor = timeZoneMonitor,

core/data/src/main/kotlin/com/google/samples/apps/nowinandroid/core/data/util/ErrorMonitor.kt

@@ -22,7 +22,11 @@ import kotlinx.coroutines.flow.Flow
  * Interface for handling error messages.
  */
 interface ErrorMonitor {
-    fun addErrorMessage(error: String): String?
+    fun addShortErrorMessage(error: String, label: String? = null, successAction: (() -> Unit)? = null, failureAction: (() -> Unit)? = null): String?
+    fun addLongErrorMessage(error: String, label: String? = null, successAction: (() -> Unit)? = null, failureAction: (() -> Unit)? = null): String?
+    fun addIndefiniteErrorMessage(error: String, label: String? = null, successAction: (() -> Unit)? = null, failureAction: (() -> Unit)? = null): String?
     fun clearErrorMessage(id: String)
-    val errorMessages: Flow<List<ErrorMessage?>>
+    val errorMessage: Flow<ErrorMessage?>
+    val isOffline: Flow<Boolean>
+    var offlineMessage: String?
 }

core/data/src/main/kotlin/com/google/samples/apps/nowinandroid/core/data/util/SnackbarErrorMonitor.kt

@@ -18,6 +18,8 @@ package com.google.samples.apps.nowinandroid.core.data.util
 
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.combine
+import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.update
 import java.util.UUID
 import javax.inject.Inject
@@ -26,12 +28,25 @@ import javax.inject.Inject
  * Interface implementation for handling general errors.
  */
 
-class SnackbarErrorMonitor @Inject constructor() : ErrorMonitor {
+class SnackbarErrorMonitor @Inject constructor(val networkMonitor: NetworkMonitor) : ErrorMonitor {
     /**
      * List of [ErrorMessage] to be shown to the user, via Snackbar.
      */
-    private val _errorMessages = MutableStateFlow<List<ErrorMessage>>(emptyList())
-    override val errorMessages: Flow<List<ErrorMessage>> = _errorMessages
+    private val errorMessages = MutableStateFlow<List<ErrorMessage>>(emptyList())
+
+    override val isOffline = networkMonitor.isOnline
+        .map(Boolean::not)
+
+    override var offlineMessage: String? = null
+
+    override val errorMessage: Flow<ErrorMessage?> = combine(errorMessages, isOffline) { messages, isOffline ->
+        // Offline Error Message takes precedence over other messages
+        if (isOffline) {
+            ErrorMessage(offlineMessage ?: "You are offline", duration = MessageDuration.Indefinite)
+        } else {
+            messages.firstOrNull()
+        }
+    }
 
     /**
      * Creates an [ErrorMessage] from String value and adds it to the list.
@@ -41,20 +56,32 @@ class SnackbarErrorMonitor @Inject constructor() : ErrorMonitor {
      * Returns the ID of the new [ErrorMessage] if success
      * Returns null if [error] is Blank
      */
-    override fun addErrorMessage(error: String): String? {
+    private fun addErrorMessage(error: String, label: String?, duration: MessageDuration?, actionPerformed: (() -> Unit)?, actionNotPerformed: (() -> Unit)?): String? {
         if (error.isNotBlank()) {
-            val newError = ErrorMessage(error)
-            _errorMessages.update { it + newError }
+            val newError = ErrorMessage(error, label = label, duration = duration, actionPerformed = actionPerformed, actionNotPerformed = actionNotPerformed)
+            errorMessages.update { it + newError }
             return newError.id
         }
         return null
     }
 
+    override fun addShortErrorMessage(error: String, label: String?, successAction: (() -> Unit)?, failureAction: (() -> Unit)?): String? {
+        return addErrorMessage(error, label, MessageDuration.Short, successAction, failureAction)
+    }
+
+    override fun addLongErrorMessage(error: String, label: String?, successAction: (() -> Unit)?, failureAction: (() -> Unit)?): String? {
+        return addErrorMessage(error, label, MessageDuration.Long, successAction, failureAction)
+    }
+
+    override fun addIndefiniteErrorMessage(error: String, label: String?, successAction: (() -> Unit)?, failureAction: (() -> Unit)?): String? {
+        return addErrorMessage(error, label, MessageDuration.Indefinite, successAction, failureAction)
+    }
+
     /**
      * Removes the [ErrorMessage] with the specified [id] from the list.
      */
     override fun clearErrorMessage(id: String) {
-        _errorMessages.update { it.filter { item -> item.id != id } }
+        errorMessages.update { it.filter { item -> item.id != id } }
     }
 }
 
@@ -64,4 +91,14 @@ class SnackbarErrorMonitor @Inject constructor() : ErrorMonitor {
 data class ErrorMessage(
     val message: String,
     val id: String = UUID.randomUUID().toString(),
+    val label: String? = null,
+    val duration: MessageDuration? = MessageDuration.Short,
+    val actionPerformed: (() -> Unit)? = null,
+    val actionNotPerformed: (() -> Unit)? = null,
 )
+
+enum class MessageDuration {
+    Short,
+    Long,
+    Indefinite,
+}

feature/bookmarks/src/androidTest/kotlin/com/google/samples/apps/nowinandroid/feature/bookmarks/BookmarksScreenTest.kt

@@ -55,7 +55,7 @@ class BookmarksScreenTest {
         composeTestRule.setContent {
             BookmarksScreen(
                 feedState = NewsFeedUiState.Loading,
-                onShowSnackbar = { _, _ -> false },
+                onShowSnackbar = { _, _, _, _ -> Unit },
                 removeFromBookmarks = {},
                 onTopicClick = {},
                 onNewsResourceViewed = {},
@@ -76,7 +76,7 @@ class BookmarksScreenTest {
                 feedState = NewsFeedUiState.Success(
                     userNewsResourcesTestData.take(2),
                 ),
-                onShowSnackbar = { _, _ -> false },
+                onShowSnackbar = { _, _, _, _ -> Unit },
                 removeFromBookmarks = {},
                 onTopicClick = {},
                 onNewsResourceViewed = {},
@@ -117,7 +117,7 @@ class BookmarksScreenTest {
                 feedState = NewsFeedUiState.Success(
                     userNewsResourcesTestData.take(2),
                 ),
-                onShowSnackbar = { _, _ -> false },
+                onShowSnackbar = { _, _, _, _ -> Unit },
                 removeFromBookmarks = { newsResourceId ->
                     assertEquals(userNewsResourcesTestData[0].id, newsResourceId)
                     removeFromBookmarksCalled = true
@@ -152,7 +152,7 @@ class BookmarksScreenTest {
         composeTestRule.setContent {
             BookmarksScreen(
                 feedState = NewsFeedUiState.Success(emptyList()),
-                onShowSnackbar = { _, _ -> false },
+                onShowSnackbar = { _, _, _, _ -> Unit },
                 removeFromBookmarks = {},
                 onTopicClick = {},
                 onNewsResourceViewed = {},
@@ -181,7 +181,7 @@ class BookmarksScreenTest {
             CompositionLocalProvider(LocalLifecycleOwner provides testLifecycleOwner) {
                 BookmarksScreen(
                     feedState = NewsFeedUiState.Success(emptyList()),
-                    onShowSnackbar = { _, _ -> false },
+                    onShowSnackbar = { _, _, _, _ -> Unit },
                     removeFromBookmarks = {},
                     onTopicClick = {},
                     onNewsResourceViewed = {},

feature/bookmarks/src/main/kotlin/com/google/samples/apps/nowinandroid/feature/bookmarks/BookmarksScreen.kt

@@ -78,7 +78,7 @@ import com.google.samples.apps.nowinandroid.core.ui.newsFeed
 @Composable
 internal fun BookmarksRoute(
     onTopicClick: (String) -> Unit,
-    onShowSnackbar: suspend (String, String?) -> Boolean,
+    onShowSnackbar: (String, String?, (() -> Unit)?, (() -> Unit)?) -> Unit,
     modifier: Modifier = Modifier,
     viewModel: BookmarksViewModel = hiltViewModel(),
 ) {
@@ -103,7 +103,7 @@ internal fun BookmarksRoute(
 @Composable
 internal fun BookmarksScreen(
     feedState: NewsFeedUiState,
-    onShowSnackbar: suspend (String, String?) -> Boolean,
+    onShowSnackbar: (String, String?, (() -> Unit)?, (() -> Unit)?) -> Unit,
     removeFromBookmarks: (String) -> Unit,
     onNewsResourceViewed: (String) -> Unit,
     onTopicClick: (String) -> Unit,
@@ -117,12 +117,7 @@ internal fun BookmarksScreen(
 
     LaunchedEffect(shouldDisplayUndoBookmark) {
         if (shouldDisplayUndoBookmark) {
-            val snackBarResult = onShowSnackbar(bookmarkRemovedMessage, undoText)
-            if (snackBarResult) {
-                undoBookmarkRemoval()
-            } else {
-                clearUndoState()
-            }
+            onShowSnackbar(bookmarkRemovedMessage, undoText, { undoBookmarkRemoval() }, { clearUndoState() })
         }
     }
 

feature/bookmarks/src/main/kotlin/com/google/samples/apps/nowinandroid/feature/bookmarks/navigation/BookmarksNavigation.kt

@@ -28,7 +28,7 @@ fun NavController.navigateToBookmarks(navOptions: NavOptions) = navigate(BOOKMAR
 
 fun NavGraphBuilder.bookmarksScreen(
     onTopicClick: (String) -> Unit,
-    onShowSnackbar: suspend (String, String?) -> Boolean,
+    onShowSnackbar: (String, String?, (() -> Unit)?, (() -> Unit)?) -> Unit,
 ) {
     composable(route = BOOKMARKS_ROUTE) {
         BookmarksRoute(onTopicClick, onShowSnackbar)