fix: show correct placeholder states in single-note widget

Three distinct states are now handled correctly:

- Startup / system update: the widget shows "Loading note…" while the
  RemoteViewsAdapter connects. updateAppWidget() sets the placeholder
  visible with that text on every full reset (ACTION_APPWIDGET_UPDATE).

- Note refresh (edit or sync): updateSingleNoteWidgets() now sends a
  custom ACTION_DATA_CHANGED instead of ACTION_APPWIDGET_UPDATE. onReceive()
  handles this with notifyAppWidgetViewDataChanged() only, leaving the
  existing RemoteViews intact so the note content updates in place with
  no blank gap or flash.

- Note missing: once onDataSetChanged() confirms getNoteById() returns null,
  partiallyUpdateAppWidget() sets the placeholder visible with "Note not found".
  When the note is found the placeholder is hidden via the same mechanism.

Fixes #1611

AI-assisted: Claude Code (Sonnet 4.6)
Signed-off-by: Jan C. Borchardt <925062+jancborchardt@users.noreply.github.com>

Author: jancborchardt

app/src/main/java/it/niedermann/owncloud/notes/widget/singlenote/SingleNoteWidget.kt

@@ -12,6 +12,7 @@ import android.appwidget.AppWidgetProvider
 import android.content.ComponentName
 import android.content.Context
 import android.content.Intent
+import android.view.View
 import android.widget.RemoteViews
 import androidx.core.net.toUri
 import it.niedermann.owncloud.notes.R
@@ -35,10 +36,16 @@ class SingleNoteWidget : AppWidgetProvider() {
     override fun onReceive(context: Context, intent: Intent?) {
         super.onReceive(context, intent)
         val awm = AppWidgetManager.getInstance(context)
-
         val provider = ComponentName(context, SingleNoteWidget::class.java)
         val appWidgetIds = awm.getAppWidgetIds(provider)
-        updateAppWidget(context, awm, appWidgetIds)
+
+        if (intent?.action == ACTION_DATA_CHANGED) {
+            appWidgetIds.forEach { appWidgetId ->
+                awm.notifyAppWidgetViewDataChanged(appWidgetId, R.id.single_note_widget_lv)
+            }
+        } else {
+            updateAppWidget(context, awm, appWidgetIds)
+        }
     }
 
     override fun onDeleted(context: Context, appWidgetIds: IntArray) {
@@ -104,19 +111,19 @@ class SingleNoteWidget : AppWidgetProvider() {
             R.layout.widget_single_note
         ).apply {
             setPendingIntentTemplate(R.id.single_note_widget_lv, pendingIntent)
-            setEmptyView(
-                R.id.single_note_widget_lv,
-                R.id.widget_single_note_placeholder_tv
-            )
             setRemoteAdapter(R.id.single_note_widget_lv, serviceIntent)
+            setViewVisibility(R.id.widget_single_note_placeholder_tv, View.VISIBLE)
+            setTextViewText(R.id.widget_single_note_placeholder_tv, context.getString(R.string.widget_single_note_loading))
         }
     }
 
     companion object {
+        private const val ACTION_DATA_CHANGED = "it.niedermann.owncloud.notes.ACTION_WIDGET_DATA_CHANGED"
+
         @JvmStatic
         fun updateSingleNoteWidgets(context: Context) {
             val intent = Intent(context, SingleNoteWidget::class.java).apply {
-                setAction(AppWidgetManager.ACTION_APPWIDGET_UPDATE)
+                action = ACTION_DATA_CHANGED
             }
             context.sendBroadcast(intent)
         }

app/src/main/java/it/niedermann/owncloud/notes/widget/singlenote/SingleNoteWidgetFactory.java

@@ -10,6 +10,7 @@
 import android.content.Context;
 import android.content.Intent;
 import android.util.Log;
+import android.view.View;
 import android.widget.RemoteViews;
 import android.widget.RemoteViewsService;
 
@@ -53,9 +54,16 @@ public void onDataSetChanged() {
             Log.v(TAG, "Fetch note with id " + noteId);
             note = repo.getNoteById(noteId);
 
+            final var views = new RemoteViews(context.getPackageName(), R.layout.widget_single_note);
             if (note == null) {
                 Log.e(TAG, "Error: note not found");
+                views.setViewVisibility(R.id.widget_single_note_placeholder_tv, View.VISIBLE);
+                views.setTextViewText(R.id.widget_single_note_placeholder_tv,
+                        context.getString(R.string.widget_single_note_note_not_found));
+            } else {
+                views.setViewVisibility(R.id.widget_single_note_placeholder_tv, View.GONE);
             }
+            AppWidgetManager.getInstance(context).partiallyUpdateAppWidget(appWidgetId, views);
         } else {
             Log.w(TAG, "Widget with ID " + appWidgetId + " seems to be not configured yet.");
         }
@@ -110,7 +118,6 @@ public RemoteViews getViewAt(int position) {
     }
 
 
-    // TODO Set loading view
     @Override
     public RemoteViews getLoadingView() {
         return null;

app/src/main/res/layout/widget_single_note.xml

@@ -25,8 +25,9 @@
         android:layout_height="match_parent"
         android:gravity="center"
         android:padding="@dimen/spacer_1x"
-        android:text="@string/widget_single_note_placeholder_tv"
+        android:text="@string/widget_single_note_note_not_found"
         android:textAlignment="center"
-        android:textColor="@color/widget_foreground" />
+        android:textColor="@color/widget_foreground"
+        android:visibility="gone" />
 
 </RelativeLayout>

app/src/main/res/values/strings.xml

@@ -241,7 +241,8 @@
     <string name="widget_note_list_title">Note list</string>
     <string name="widget_note_list_placeholder">No notes</string>
     <string name="widget_single_note_title">Single note</string>
-    <string name="widget_single_note_placeholder_tv">Note not found</string>
+    <string name="widget_single_note_loading">Loading note…</string>
+    <string name="widget_single_note_note_not_found">Note not found</string>
     <string name="widget_not_logged_in">Please login to Notes before using this widget</string>
     <string name="widget_entry_fav_contentDescription">Star icon is used to denote an item as a favorite</string>