feat: add loading and error widget support for StacNetworkWidget

packages/stac/lib/src/parsers/widgets/stac_network_widget/stac_network_widget_parser.dart

@@ -1,5 +1,6 @@
 import 'package:flutter/cupertino.dart';
 import 'package:stac/src/framework/framework.dart';
+import 'package:stac/src/parsers/core/stac_widget_parser.dart';
 import 'package:stac_core/stac_core.dart';
 import 'package:stac_framework/stac_framework.dart';
 
@@ -15,6 +16,16 @@ class StacNetworkWidgetParser extends StacParser<StacNetworkWidget> {
 
   @override
   Widget parse(BuildContext context, StacNetworkWidget model) {
-    return Stac.fromNetwork(context: context, request: model.request);
+    return Stac.fromNetwork(
+      context: context,
+      request: model.request,
+      loadingWidget: model.loadingWidget != null
+          ? (context) => model.loadingWidget!.parse(context) ?? const SizedBox()
+          : null,
+      errorWidget: model.errorWidget != null
+          ? (context, error) =>
+                model.errorWidget!.parse(context) ?? const SizedBox()
+          : null,
+    );
   }
 }

packages/stac_core/lib/widgets/network_widget/stac_network_widget.dart

@@ -8,7 +8,8 @@ part 'stac_network_widget.g.dart';
 /// A Stac model representing a network-driven widget.
 ///
 /// This widget triggers a [StacNetworkRequest] to fetch a Stac UI JSON from a
-/// URL and renders it.
+/// URL and renders it. Optionally, you can provide custom loading and error
+/// widgets to display during the network request lifecycle.
 ///
 /// {@tool snippet}
 /// Dart Example:
@@ -18,6 +19,12 @@ part 'stac_network_widget.g.dart';
 ///     url: 'https://example.com/data',
 ///     method: 'get',
 ///   ),
+///   loadingWidget: StacCenter(
+///     child: StacCircularProgressIndicator(),
+///   ),
+///   errorWidget: StacCenter(
+///     child: StacText(data: 'Failed to load'),
+///   ),
 /// )
 /// ```
 /// {@end-tool}
@@ -31,18 +38,51 @@ part 'stac_network_widget.g.dart';
 ///     "actionType": "networkRequest",
 ///     "url": "https://example.com/data",
 ///     "method": "get"
+///   },
+///   "loadingWidget": {
+///     "type": "center",
+///     "child": {
+///       "type": "circularProgressIndicator"
+///     }
+///   },
+///   "errorWidget": {
+///     "type": "center",
+///     "child": {
+///       "type": "text",
+///       "data": "Failed to load"
+///     }
 ///   }
 /// }
 /// ```
 /// {@end-tool}
 @JsonSerializable()
 class StacNetworkWidget extends StacWidget {
   /// Creates a [StacNetworkWidget].
-  const StacNetworkWidget({required this.request});
+  ///
+  /// The [request] parameter is required and defines the network request
+  /// to execute. The [loadingWidget] and [errorWidget] parameters are
+  /// optional and allow you to customize the loading and error states.
+  const StacNetworkWidget({
+    required this.request,
+    this.loadingWidget,
+    this.errorWidget,
+  });
 
   /// The network request to execute.
+  ///
+  /// This defines the URL, method, headers, and body for the network request.
   final StacNetworkRequest request;
 
+  /// Optional widget to display while the network request is in progress.
+  ///
+  /// If not provided, a default loading indicator is shown.
+  final StacWidget? loadingWidget;
+
+  /// Optional widget to display when the network request fails.
+  ///
+  /// If not provided, an empty [SizedBox] is shown on error.
+  final StacWidget? errorWidget;
+
   /// Widget type identifier.
   @override
   String get type => WidgetType.networkWidget.name;