Enable 'Next Article' (#171)

app/src/main/java/me/ash/reader/ui/page/common/HomeEntry.kt

@@ -132,7 +132,7 @@ fun HomeEntry(
                 )
             }
             animatedComposable(route = "${RouteName.READING}/{articleId}") {
-                ReadingPage(navController = navController)
+                ReadingPage(navController = navController, homeViewModel = homeViewModel)
             }
 
             // Settings

app/src/main/java/me/ash/reader/ui/page/home/HomeViewModel.kt

@@ -99,4 +99,5 @@ data class FilterState(
 data class HomeUiState(
     val pagingData: Flow<PagingData<ArticleFlowItem>> = emptyFlow(),
     val searchContent: String = "",
+    var nextArticleId: String = ""
 )

app/src/main/java/me/ash/reader/ui/page/home/reading/BottomBar.kt

@@ -33,6 +33,7 @@ fun BottomBar(
     isFullContent: Boolean,
     onUnread: (isUnread: Boolean) -> Unit = {},
     onStarred: (isStarred: Boolean) -> Unit = {},
+    onNextArticle: () -> Unit = {},
     onFullContent: (isFullContent: Boolean) -> Unit = {},
 ) {
     val tonalElevation = LocalReadingPageTonalElevation.current
@@ -95,13 +96,14 @@ fun BottomBar(
                         onStarred(!isStarred)
                     }
                     CanBeDisabledIconButton(
-                        disabled = true,
+                        disabled = false,
                         modifier = Modifier.size(40.dp),
                         imageVector = Icons.Rounded.ExpandMore,
                         contentDescription = "Next Article",
                         tint = MaterialTheme.colorScheme.outline,
                     ) {
                         view.performHapticFeedback(HapticFeedbackConstants.KEYBOARD_TAP)
+                        onNextArticle()
                     }
                     CanBeDisabledIconButton(
                         modifier = Modifier.size(36.dp),

app/src/main/java/me/ash/reader/ui/page/home/reading/ReadingPage.kt

@@ -9,25 +9,32 @@ import androidx.compose.ui.Modifier
 import androidx.compose.ui.unit.dp
 import androidx.hilt.navigation.compose.hiltViewModel
 import androidx.navigation.NavHostController
+import androidx.paging.compose.collectAsLazyPagingItems
 import me.ash.reader.data.model.preference.LocalReadingAutoHideToolbar
 import me.ash.reader.data.model.preference.LocalReadingPageTonalElevation
 import me.ash.reader.ui.component.base.RYScaffold
 import me.ash.reader.ui.ext.collectAsStateValue
 import me.ash.reader.ui.ext.isScrollDown
+import me.ash.reader.ui.page.home.HomeViewModel
 
 @Composable
 fun ReadingPage(
     navController: NavHostController,
+    homeViewModel: HomeViewModel,
     readingViewModel: ReadingViewModel = hiltViewModel(),
 ) {
     val tonalElevation = LocalReadingPageTonalElevation.current
     val readingUiState = readingViewModel.readingUiState.collectAsStateValue()
+    val homeUiState = homeViewModel.homeUiState.collectAsStateValue()
     val isShowToolBar = if (LocalReadingAutoHideToolbar.current.value) {
         readingUiState.articleWithFeed != null && !readingUiState.listState.isScrollDown()
     } else {
         true
     }
 
+    val pagingItems = homeUiState.pagingData.collectAsLazyPagingItems().itemSnapshotList
+    readingViewModel.recorderNextArticle(readingUiState, homeUiState, pagingItems)
+
     LaunchedEffect(Unit) {
         navController.currentBackStackEntryFlow.collect {
             it.arguments?.getString("articleId")?.let {
@@ -90,6 +97,9 @@ fun ReadingPage(
                         onStarred = {
                             readingViewModel.markStarred(it)
                         },
+                        onNextArticle = {
+                            readingViewModel.nextArticle(navController, homeUiState.nextArticleId)
+                        },
                         onFullContent = {
                             if (it) readingViewModel.renderFullContent()
                             else readingViewModel.renderDescriptionContent()

app/src/main/java/me/ash/reader/ui/page/home/reading/ReadingViewModel.kt

@@ -4,6 +4,8 @@ import android.util.Log
 import androidx.compose.foundation.lazy.LazyListState
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
+import androidx.navigation.NavController
+import androidx.paging.ItemSnapshotList
 import dagger.hilt.android.lifecycle.HiltViewModel
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.flow.MutableStateFlow
@@ -11,9 +13,12 @@ import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.asStateFlow
 import kotlinx.coroutines.flow.update
 import kotlinx.coroutines.launch
+import me.ash.reader.data.model.article.ArticleFlowItem
 import me.ash.reader.data.model.article.ArticleWithFeed
 import me.ash.reader.data.repository.RssHelper
 import me.ash.reader.data.repository.RssRepository
+import me.ash.reader.ui.page.common.RouteName
+import me.ash.reader.ui.page.home.HomeUiState
 import javax.inject.Inject
 
 @HiltViewModel
@@ -114,6 +119,13 @@ class ReadingViewModel @Inject constructor(
         }
     }
 
+    fun nextArticle(navController: NavController, nextArticleId: String) {
+        navController.popBackStack()
+        if (nextArticleId.isNotBlank()) {
+            navController.navigate("${RouteName.READING}/${nextArticleId}")
+        }
+    }
+
     private fun showLoading() {
         _readingUiState.update {
             it.copy(isLoading = true)
@@ -125,6 +137,30 @@ class ReadingViewModel @Inject constructor(
             it.copy(isLoading = false)
         }
     }
+
+    fun recorderNextArticle(
+        readingUiState: ReadingUiState, homeUiState: HomeUiState, pagingItems:
+        ItemSnapshotList<ArticleFlowItem>
+    ) {
+        if (pagingItems.size > 0) {
+            val cur = readingUiState.articleWithFeed?.article
+            if (cur != null) {
+                var found = false
+                for (item in pagingItems) {
+                    if (item is ArticleFlowItem.Article) {
+                        val itemId = item.articleWithFeed.article.id
+                        if (itemId == cur.id) {
+                            found = true
+                            homeUiState.nextArticleId = ""
+                        } else if (found) {
+                            homeUiState.nextArticleId = itemId
+                            break
+                        }
+                    }
+                }
+            }
+        }
+    }
 }
 
 data class ReadingUiState(