Fix reader loading indefinitely in some scenarios (#3686)

Init the reader from the view model instead of the activity so it isn't
cancelled by a configuration change mid init, which left the retained
view model half initialized and needsInit() returning false.

Assisted-by: Claude Code:claude-opus-5

CHANGELOG.md

@@ -23,6 +23,7 @@ The format is a modified version of [Keep a Changelog](https://keepachangelog.co
 ### Fixed
 - Fixed extension installation with shizuku installer ([@NGB-Was-Taken](https://github.com/NGB-Was-Taken)) ([#3676](https://github.com/mihonapp/mihon/pull/3676))
 - Fixed `X-Requested-With` spoofing leaking to unrelated callers ([@AntsyLich](https://github.com/AntsyLich)) ([#3678](https://github.com/mihonapp/mihon/pull/3678))
+- Fixed reader loading indefinitely in some scenarios ([@AntsyLich](https://github.com/AntsyLich)) ([#3686](https://github.com/mihonapp/mihon/pull/3686))
 
 ## [v0.20.2] - 2026-08-01
 ### Added

app/src/main/java/eu/kanade/tachiyomi/ui/reader/ReaderActivity.kt

@@ -98,7 +98,6 @@ import tachiyomi.core.common.Constants
 import tachiyomi.core.common.i18n.stringResource
 import tachiyomi.core.common.util.lang.launchIO
 import tachiyomi.core.common.util.lang.launchNonCancellable
-import tachiyomi.core.common.util.lang.withUIContext
 import tachiyomi.core.common.util.system.logcat
 import tachiyomi.i18n.MR
 import tachiyomi.presentation.core.util.collectAsState
@@ -171,26 +170,17 @@ class ReaderActivity : BaseActivity() {
         setContentView(binding.root)
         binding.setComposeOverlay()
 
-        if (viewModel.needsInit()) {
-            val manga = intent.extras?.getLong("manga", -1) ?: -1L
-            val chapter = intent.extras?.getLong("chapter", -1) ?: -1L
-            if (manga == -1L || chapter == -1L) {
-                finish()
-                return
-            }
-            NotificationReceiver.dismissNotification(this, manga.hashCode(), Notifications.ID_NEW_CHAPTERS)
-
-            lifecycleScope.launch {
-                val initResult = viewModel.init(manga, chapter)
-                if (!initResult.getOrDefault(false)) {
-                    val exception = initResult.exceptionOrNull() ?: IllegalStateException("Unknown err")
-                    withUIContext {
-                        setInitialChapterError(exception)
-                    }
-                }
-            }
+        if (!viewModel.hasValidArgs) {
+            finish()
+            return
         }
 
+        NotificationReceiver.dismissNotification(
+            this,
+            viewModel.mangaId.hashCode(),
+            Notifications.ID_NEW_CHAPTERS,
+        )
+
         config = ReaderConfig()
         setMenuVisibility(viewModel.state.value.menuVisible)
 
@@ -200,6 +190,13 @@ class ReaderActivity : BaseActivity() {
             .onEach { if (!it) finish() }
             .launchIn(lifecycleScope)
 
+        viewModel.state
+            .map { it.initError }
+            .distinctUntilChanged()
+            .filterNotNull()
+            .onEach(::setInitialChapterError)
+            .launchIn(lifecycleScope)
+
         viewModel.state
             .map { it.isLoadingAdjacentChapter }
             .distinctUntilChanged()

app/src/main/java/eu/kanade/tachiyomi/ui/reader/ReaderViewModel.kt

@@ -53,6 +53,7 @@ import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.onEach
 import kotlinx.coroutines.flow.receiveAsFlow
 import kotlinx.coroutines.flow.update
+import kotlinx.coroutines.launch
 import kotlinx.coroutines.runBlocking
 import logcat.LogPriority
 import tachiyomi.core.common.preference.toggle
@@ -107,6 +108,14 @@ class ReaderViewModel @JvmOverloads constructor(
     private val mutableState = MutableStateFlow(State())
     val state = mutableState.asStateFlow()
 
+    /**
+     * Ids of the manga and chapter the reader was launched with, taken from the activity intent.
+     */
+    val mangaId = savedState.get<Long>("manga") ?: -1L
+    private val initialChapterId = savedState.get<Long>("chapter") ?: -1L
+
+    val hasValidArgs = mangaId != -1L && initialChapterId != -1L
+
     private val eventChannel = Channel<Event>()
     val eventFlow = eventChannel.receiveAsFlow()
 
@@ -244,6 +253,10 @@ class ReaderViewModel @JvmOverloads constructor(
                 chapterId = currentChapter.chapter.id!!
             }
             .launchIn(viewModelScope)
+
+        if (hasValidArgs) {
+            viewModelScope.launch { init() }
+        }
     }
 
     override fun onCleared() {
@@ -265,41 +278,28 @@ class ReaderViewModel @JvmOverloads constructor(
     }
 
     /**
-     * Whether this presenter is initialized yet.
+     * Initializes this presenter with the [mangaId] and [initialChapterId] the reader was launched
+     * with. This method will fetch the manga from the database and initialize the initial chapter.
+     * Failures are reported through [State.initError].
      */
-    fun needsInit(): Boolean {
-        return manga == null
-    }
-
-    /**
-     * Initializes this presenter with the given [mangaId] and [initialChapterId]. This method will
-     * fetch the manga from the database and initialize the initial chapter.
-     */
-    suspend fun init(mangaId: Long, initialChapterId: Long): Result<Boolean> {
-        if (!needsInit()) return Result.success(true)
-        return withIOContext {
+    private suspend fun init() {
+        withIOContext {
             try {
-                val manga = getManga.await(mangaId)
-                if (manga != null) {
-                    sourceManager.isInitialized.first { it }
-                    mutableState.update { it.copy(manga = manga) }
-                    if (chapterId == -1L) chapterId = initialChapterId
+                val manga = getManga.await(mangaId) ?: error("Requested manga of id $mangaId not found")
+                sourceManager.isInitialized.first { it }
+                mutableState.update { it.copy(manga = manga) }
+                if (chapterId == -1L) chapterId = initialChapterId
 
-                    val context = Injekt.get<Application>()
-                    val source = sourceManager.getOrStub(manga.source)
-                    loader = ChapterLoader(context, downloadManager, downloadProvider, manga, source)
+                val context = Injekt.get<Application>()
+                val source = sourceManager.getOrStub(manga.source)
+                loader = ChapterLoader(context, downloadManager, downloadProvider, manga, source)
 
-                    loadChapter(loader!!, chapterList.first { chapterId == it.chapter.id })
-                    Result.success(true)
-                } else {
-                    // Unlikely but okay
-                    Result.success(false)
-                }
+                loadChapter(loader!!, chapterList.first { chapterId == it.chapter.id })
             } catch (e: Throwable) {
                 if (e is CancellationException) {
                     throw e
                 }
-                Result.failure(e)
+                mutableState.update { it.copy(initError = e) }
             }
         }
     }
@@ -948,6 +948,7 @@ class ReaderViewModel @JvmOverloads constructor(
     @Immutable
     data class State(
         val manga: Manga? = null,
+        val initError: Throwable? = null,
         val viewerChapters: ViewerChapters? = null,
         val bookmarked: Boolean = false,
         val isLoadingAdjacentChapter: Boolean = false,