ankidroid · sanjaysargam · Jan 5, 2026
diff --git a/AnkiDroid/src/main/java/com/ichi2/anki/AbstractFlashcardViewer.kt b/AnkiDroid/src/main/java/com/ichi2/anki/AbstractFlashcardViewer.kt
@@ -799,7 +799,7 @@ abstract class AbstractFlashcardViewer :
         }
         val animation = fromGesture.toAnimationTransition().invert()
         Timber.i("Launching 'edit card'")
-        val editCardIntent = NoteEditorLauncher.EditCard(currentCard!!.id, animation).toIntent(this)
+        val editCardIntent = NoteEditorLauncher.EditSelection(currentCard!!.id, animation).toIntent(this)
         editCurrentCardLauncher.launch(editCardIntent)
     }
 

diff --git a/AnkiDroid/src/main/java/com/ichi2/anki/CardBrowser.kt b/AnkiDroid/src/main/java/com/ichi2/anki/CardBrowser.kt
@@ -127,7 +127,7 @@ open class CardBrowser :
      */
     private val editNoteLauncher: NoteEditorLauncher
         get() =
-            NoteEditorLauncher.EditCard(viewModel.currentCardId, Direction.DEFAULT, fragmented).also {
+            NoteEditorLauncher.EditSelection(viewModel.currentCardId, Direction.DEFAULT, fragmented).also {
                 Timber.i("editNoteLauncher: %s", it)
             }
 
@@ -709,18 +709,22 @@ open class CardBrowser :
         cardBrowserFragment.updateFlagForSelectedRows(flag)
     }
 
-    /** Opens the note editor for a card.
-     * We use the Card ID to specify the preview target  */
+    /**
+     * Opens the note editor for the given card.
+     *
+     * @param cardId The ID of the card to open in the note editor.
+     * Passing `null` indicates that no card is selected and will close the note editor
+     */
     @NeedsTest("note edits are saved")
     @NeedsTest("I/O edits are saved")
-    fun openNoteEditorForCard(cardId: CardId) {
-        viewModel.openNoteEditorForCard(cardId)
+    fun setNoteEditorCard(cardId: CardId?) {
+        viewModel.setNoteEditorCard(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)
@@ -739,7 +743,7 @@ open class CardBrowser :
 
             try {
                 val cardId = getCardIdForNoteEditor()
-                openNoteEditorForCard(cardId)
+                setNoteEditorCard(cardId)
             } catch (e: Exception) {
                 Timber.w(e, "Error Opening Note Editor")
                 showSnackbar(R.string.multimedia_editor_something_wrong)
@@ -1143,10 +1147,10 @@ open class CardBrowser :
             updateList()
             // Check whether deck is empty or not
             val isDeckEmpty = viewModel.rowCount == 0
+            val currentCardId = viewModel.updateCurrentCardId()
             // 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)
+                if (fragmented && !isDeckEmpty && currentCardId != null) {
                     loadNoteEditorFragmentIfFragmented()
                     View.VISIBLE
                 } else {

diff --git a/AnkiDroid/src/main/java/com/ichi2/anki/browser/CardBrowserFragment.kt b/AnkiDroid/src/main/java/com/ichi2/anki/browser/CardBrowserFragment.kt
@@ -653,7 +653,7 @@ class CardBrowserFragment :
                 }
             } else {
                 val cardId = activityViewModel.queryDataForCardEdit(id)
-                requireCardBrowserActivity().openNoteEditorForCard(cardId)
+                requireCardBrowserActivity().setNoteEditorCard(cardId)
             }
         }
 

diff --git a/AnkiDroid/src/main/java/com/ichi2/anki/browser/CardBrowserViewModel.kt b/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
+
+    /**
+     * Computes and stores the current card ID used by the note editor.
+     */
+    suspend fun updateCurrentCardId(): CardId? {
+        currentCardId =
+            // Early return if no cards available
+            if (cards.isEmpty()) {
+                null
+            } else {
+                focusedRow?.toCardId(cardsOrNotes)
+                    ?: cards.firstOrNull()?.toCardId(cardsOrNotes)
+            }
+        return currentCardId
+    }
 
     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
@@ -564,8 +579,13 @@ class CardBrowserViewModel(
         }
     }
 
-    // on a row tap
-    fun openNoteEditorForCard(cardId: CardId) {
+    /**
+     * Opens the note editor for the given card.
+     *
+     * @param cardId The ID of the card to open in the note editor.
+     * Passing `null` indicates that no card is selected and will close the note editor
+     */
+    fun setNoteEditorCard(cardId: CardId?) {
         currentCardId = cardId
         if (!isFragmented) {
             endMultiSelectMode(SingleSelectCause.OpenNoteEditorActivity)
@@ -1236,7 +1256,7 @@ 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

diff --git a/AnkiDroid/src/main/java/com/ichi2/anki/browser/CardOrNoteId.kt b/AnkiDroid/src/main/java/com/ichi2/anki/browser/CardOrNoteId.kt
@@ -39,9 +39,16 @@ 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 =
+
+    // TODO: Notes without cards likely indicate an invalid or corrupted collection state.
+    //  We currently handle this gracefully by returning an empty list,
+    //  we may want to surface this as a warning or integrity check for the user.
+    suspend fun toCardId(type: CardsOrNotes): CardId? =
         when (type) {
             CardsOrNotes.CARDS -> cardOrNoteId
-            CardsOrNotes.NOTES -> withCol { cardIdsOfNote(cardOrNoteId).first() }
+            // A note can map to multiple cards or none at all.
+            // See [cardIdsOfNote] for the full explanation and edge cases
+            // (empty templates, orphaned notes, etc).
+            CardsOrNotes.NOTES -> withCol { cardIdsOfNote(cardOrNoteId).firstOrNull() }
         }
 }
diff --git a/AnkiDroid/src/main/java/com/ichi2/anki/noteeditor/NoteEditorLauncher.kt b/AnkiDroid/src/main/java/com/ichi2/anki/noteeditor/NoteEditorLauncher.kt
@@ -164,12 +164,12 @@ sealed interface NoteEditorLauncher : Destination {
     }
 
     /**
-     * Represents editing a card in the NoteEditor.
-     * @property cardId The ID of the card to edit.
+     * Opens the NoteEditor for the current selection (card or note).
+     * @property cardId The selected card ID, or null when editing a note.
      * @property animation The animation direction.
      */
-    data class EditCard(
-        val cardId: CardId,
+    data class EditSelection(
+        val cardId: CardId?,
         val animation: ActivityTransitionAnimation.Direction,
         val inCardBrowserActivity: Boolean = false,
     ) : NoteEditorLauncher {

diff --git a/AnkiDroid/src/test/java/com/ichi2/anki/NoteEditorTest.kt b/AnkiDroid/src/test/java/com/ichi2/anki/NoteEditorTest.kt
@@ -719,7 +719,7 @@ class NoteEditorTest : RobolectricTest() {
     ): NoteEditorFragment {
         val bundle =
             when (from) {
-                REVIEWER -> NoteEditorLauncher.EditCard(n.firstCard().id, DEFAULT).toBundle()
+                REVIEWER -> NoteEditorLauncher.EditSelection(n.firstCard().id, DEFAULT).toBundle()
                 DECK_LIST -> NoteEditorLauncher.AddNote().toBundle()
             }
         return openNoteEditorWithArgs(bundle)

diff --git a/AnkiDroid/src/test/java/com/ichi2/anki/browser/CardBrowserViewModelTest.kt b/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 -> col.getCard(row.requireCardId(cardsOrNotes)).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))
+            suspendCards(cards.first().requireCardId(cardsOrNotes))
             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))
+            suspendCards(cards.first().requireCardId(cardsOrNotes))
             ensureOpsExecuted(1) {
                 selectAll()
                 toggleSuspendCards()
@@ -1263,6 +1263,24 @@ class CardBrowserViewModelTest : JvmTest() {
             }
         }
 
+    @Test
+    fun `notes mode - a note maps to all its cards`() =
+        runViewModelNotesTest(notes = 1) {
+            // One Basic+Reversed note = 2 cards
+            assertThat("one note", rowCount, equalTo(1))
+            val row = cards.single()
+            // When in NOTES mode, selecting a row should map to all its cards
+            val cardIds = BrowserRowCollection(cardsOrNotes, mutableListOf(row)).queryCardIds()
+            assertThat(
+                "a single note expands to all its cards",
+                cardIds,
+                hasSize(2),
+            )
+            for (cardId in cardIds) {
+                assertNotNull(col.getCard(cardId))
+            }
+        }
+
     private fun assertDate(str: String?) {
         // 2025-01-09 @ 18:06
         assertNotNull(str)
@@ -1447,6 +1465,9 @@ private fun AnkiTest.suspendNote(note: Note) {
     col.sched.suspendCards(note.cardIds(col))
 }
 
+suspend fun CardOrNoteId.requireCardId(cardsOrNotes: CardsOrNotes): CardId =
+    toCardId(cardsOrNotes) ?: error("Expected card ID to be non-null for $this in $cardsOrNotes mode")
+
 val CardBrowserViewModel.column1
     get() = this.activeColumns[0]
 

diff --git a/libanki/src/main/java/com/ichi2/anki/libanki/Collection.kt b/libanki/src/main/java/com/ichi2/anki/libanki/Collection.kt
@@ -683,6 +683,16 @@ class Collection(
         backend.removeNotes(noteIds = emptyList(), cardIds = cardIds)
     }
 
+    /**
+     * Returns all card IDs linked to the given note.
+     *
+     * IMPORTANT:
+     * A note may not always have cards.
+     *
+     * This can happen in cases like:
+     * - The note type has no card templates (empty cards).
+     * - Cards were deleted but the note still exists (orphaned notes).
+     */
     @CheckResult
     @LibAnkiAlias("card_ids_of_note")
     fun cardIdsOfNote(nid: NoteId): List<CardId> = backend.cardsOfNote(nid = nid)