fix(split-cardbrowser): list is empty when toggling to notes only mode

Author: sanjaysargam

AnkiDroid/src/main/java/com/ichi2/anki/CardBrowser.kt

@@ -713,19 +713,19 @@ open class CardBrowser :
      * We use the Card ID to specify the preview target  */
     @NeedsTest("note edits are saved")
     @NeedsTest("I/O edits are saved")
-    fun openNoteEditorForCard(cardId: CardId) {
+    fun openNoteEditorForCard(cardId: CardId?) {
         viewModel.openNoteEditorForCard(cardId)
     }
 
     /**
      * In case of selection, the first card that was selected, otherwise the first card of the list.
      */
-    private suspend fun getCardIdForNoteEditor(): CardId {
+    private suspend fun getCardIdForNoteEditor(): CardId? {
         // Just select the first one if there's a multiselect occurring.
         return if (viewModel.isInMultiSelectMode) {
             viewModel.querySelectedCardIdAtPosition(0)
         } else {
-            viewModel.getRowAtPosition(0).toCardId(viewModel.cardsOrNotes)
+            viewModel.getRowAtPosition(0)?.toCardId(viewModel.cardsOrNotes)
         }
     }
 
@@ -1146,7 +1146,7 @@ open class CardBrowser :
             // Hide note editor frame if deck is empty and fragmented
             binding.noteEditorFrame?.visibility =
                 if (fragmented && !isDeckEmpty) {
-                    viewModel.currentCardId = (viewModel.focusedRow ?: viewModel.cards[0]).toCardId(viewModel.cardsOrNotes)
+                    viewModel.currentCardId = viewModel.safeGetCurrentCardId()
                     loadNoteEditorFragmentIfFragmented()
                     View.VISIBLE
                 } else {

AnkiDroid/src/main/java/com/ichi2/anki/browser/CardBrowserViewModel.kt

@@ -168,7 +168,22 @@ class CardBrowserViewModel(
     val cardsOrNotes get() = flowOfCardsOrNotes.value
 
     // card that was clicked (not marked)
-    var currentCardId: CardId = 0
+    var currentCardId: CardId? = null
+
+    /**
+     * Safely determines the current card ID to display in the note editor.
+     */
+    suspend fun safeGetCurrentCardId(): CardId? {
+        // Early return if no cards available
+        if (cards.isEmpty()) return 0
+
+        // Try to use editor row first
+        val focusedCard = focusedRow?.toCardId(cardsOrNotes)
+        if (focusedCard != null) return focusedCard
+
+        // Fallback to first card in list
+        return cards.firstOrNull()?.toCardId(cardsOrNotes)
+    }
 
     var cardIdToBeScrolledTo: CardId? = null
         private set
@@ -332,7 +347,7 @@ class CardBrowserViewModel(
         return CardInfoDestination(firstSelectedCard, TR.currentCardBrowse())
     }
 
-    suspend fun queryDataForCardEdit(id: CardOrNoteId): CardId = id.toCardId(cardsOrNotes)
+    suspend fun queryDataForCardEdit(id: CardOrNoteId): CardId? = id.toCardId(cardsOrNotes)
 
     private suspend fun getInitialDeck(): SelectableDeck {
         // TODO: Handle the launch intent
@@ -565,7 +580,7 @@ class CardBrowserViewModel(
     }
 
     // on a row tap
-    fun openNoteEditorForCard(cardId: CardId) {
+    fun openNoteEditorForCard(cardId: CardId?) {
         currentCardId = cardId
         if (!isFragmented) {
             endMultiSelectMode(SingleSelectCause.OpenNoteEditorActivity)
@@ -1236,7 +1251,7 @@ class CardBrowserViewModel(
 
     suspend fun queryCardIdAtPosition(index: Int): CardId = cards.queryCardIdsAt(index).first()
 
-    suspend fun querySelectedCardIdAtPosition(index: Int): CardId = selectedRows.toList()[index].toCardId(cardsOrNotes)
+    suspend fun querySelectedCardIdAtPosition(index: Int): CardId? = selectedRows.toList()[index].toCardId(cardsOrNotes)
 
     /**
      * Obtains two lists of column headings with preview data

AnkiDroid/src/main/java/com/ichi2/anki/browser/CardOrNoteId.kt

@@ -39,9 +39,9 @@ value class CardOrNoteId(
 
     // TODO: We use this for 'Edit Note' or 'Card Info'. We should reconsider whether we ever want
     //  to move from NoteId to CardId. Our move to 'Notes' mode wasn't well thought-through
-    suspend fun toCardId(type: CardsOrNotes): CardId =
+    suspend fun toCardId(type: CardsOrNotes): CardId? =
         when (type) {
             CardsOrNotes.CARDS -> cardOrNoteId
-            CardsOrNotes.NOTES -> withCol { cardIdsOfNote(cardOrNoteId).first() }
+            CardsOrNotes.NOTES -> withCol { cardIdsOfNote(cardOrNoteId).firstOrNull() }
         }
 }

AnkiDroid/src/main/java/com/ichi2/anki/noteeditor/NoteEditorLauncher.kt

@@ -169,7 +169,7 @@ sealed interface NoteEditorLauncher : Destination {
      * @property animation The animation direction.
      */
     data class EditCard(
-        val cardId: CardId,
+        val cardId: CardId?,
         val animation: ActivityTransitionAnimation.Direction,
         val inCardBrowserActivity: Boolean = false,
     ) : NoteEditorLauncher {

AnkiDroid/src/test/java/com/ichi2/anki/browser/CardBrowserViewModelTest.kt

@@ -154,7 +154,7 @@ class CardBrowserViewModelTest : JvmTest() {
                 assertThat("Deck should be changed", col.getCard(cardId).did, equalTo(newDeck))
             }
 
-            val hasSomeDecksUnchanged = cards.any { row -> col.getCard(row.toCardId(cardsOrNotes)).did != newDeck }
+            val hasSomeDecksUnchanged = cards.any { row -> row.toCardId(cardsOrNotes)?.let { col.getCard(it) }?.did != newDeck }
             assertThat("some decks are unchanged", hasSomeDecksUnchanged)
         }
 
@@ -633,7 +633,7 @@ class CardBrowserViewModelTest : JvmTest() {
     @Test
     fun `suspend - cards - some suspended`() =
         runViewModelTest(notes = 2) {
-            suspendCards(cards.first().toCardId(cardsOrNotes))
+            cards.first().toCardId(cardsOrNotes)?.let { suspendCards(it) }
             ensureOpsExecuted(1) {
                 selectAll()
                 toggleSuspendCards()
@@ -689,7 +689,7 @@ class CardBrowserViewModelTest : JvmTest() {
     fun `suspend - notes - some cards suspended`() =
         runViewModelNotesTest(notes = 2) {
             // this suspends o single cid from a nid
-            suspendCards(cards.first().toCardId(cardsOrNotes))
+            cards.first().toCardId(cardsOrNotes)?.let { suspendCards(it) }
             ensureOpsExecuted(1) {
                 selectAll()
                 toggleSuspendCards()