Prevent underlying page from stealing focus from ResponsiveDialog.

lib/app/message.dart

@@ -32,17 +32,16 @@ Future<T?> showBlurDialog<T>({
   required BuildContext context,
   required Widget Function(BuildContext) builder,
   RouteSettings? routeSettings,
-}) async {
-  const transitionDelay = Duration(milliseconds: 150);
-  final result = await showGeneralDialog<T>(
+}) async =>
+    await showGeneralDialog<T>(
       context: context,
       barrierDismissible: true,
       barrierLabel: MaterialLocalizations.of(context).modalBarrierDismissLabel,
       pageBuilder: (ctx, anim1, anim2) => builder(ctx),
-    transitionDuration: transitionDelay,
+      transitionDuration: const Duration(milliseconds: 150),
       transitionBuilder: (ctx, anim1, anim2, child) => BackdropFilter(
-      filter:
-          ImageFilter.blur(sigmaX: 20 * anim1.value, sigmaY: 20 * anim1.value),
+        filter: ImageFilter.blur(
+            sigmaX: 20 * anim1.value, sigmaY: 20 * anim1.value),
         child: FadeTransition(
           opacity: anim1,
           child: child,
@@ -50,9 +49,3 @@ Future<T?> showBlurDialog<T>({
       ),
       routeSettings: routeSettings,
     );
-  // Make sure we wait for the dialog to fade out before returning the result.
-  // This is needed for subsequent dialogs with autofocus.
-  await Future.delayed(transitionDelay);
-
-  return result;
-}

lib/widgets/responsive_dialog.dart

@@ -39,14 +39,15 @@ class ResponsiveDialog extends StatefulWidget {
 
 class _ResponsiveDialogState extends State<ResponsiveDialog> {
   final Key _childKey = GlobalKey();
+  final _focus = FocusScopeNode();
 
   @override
-  Widget build(BuildContext context) =>
-      LayoutBuilder(builder: ((context, constraints) {
-        final l10n = AppLocalizations.of(context)!;
-        if (constraints.maxWidth < 540) {
-          // Fullscreen
-          return Scaffold(
+  void dispose() {
+    super.dispose();
+    _focus.dispose();
+  }
+
+  Widget _buildFullscreen(BuildContext context) => Scaffold(
         appBar: AppBar(
           title: widget.title,
           actions: widget.actions,
@@ -60,12 +61,13 @@ class _ResponsiveDialogState extends State<ResponsiveDialog> {
                   : null),
         ),
         body: SingleChildScrollView(
-              child: SafeArea(
-                  child: Container(key: _childKey, child: widget.child)),
+          child:
+              SafeArea(child: Container(key: _childKey, child: widget.child)),
         ),
       );
-        } else {
-          // Dialog
+
+  Widget _buildDialog(BuildContext context) {
+    final l10n = AppLocalizations.of(context)!;
     final cancelText = widget.onCancel == null && widget.actions.isEmpty
         ? l10n.s_close
         : l10n.s_cancel;
@@ -90,5 +92,22 @@ class _ResponsiveDialogState extends State<ResponsiveDialog> {
       ],
     );
   }
+
+  @override
+  Widget build(BuildContext context) =>
+      LayoutBuilder(builder: ((context, constraints) {
+        // This keeps the focus in the dialog, even if the underlying page changes.
+        return FocusScope(
+          node: _focus,
+          autofocus: true,
+          onFocusChange: (focused) {
+            if (!focused) {
+              _focus.requestFocus();
+            }
+          },
+          child: constraints.maxWidth < 540
+              ? _buildFullscreen(context)
+              : _buildDialog(context),
+        );
       }));
 }