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lib/utils/ui_utils.dart

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+import 'package:flutter/material.dart';
+
+/// User interface utilities
+
+/// Build and return a full loading page
+Widget buildLoadingPage() {
+  return Scaffold(
+    body: Center(
+      child: CircularProgressIndicator(),
+    ),
+  );
+}
+
+/// Build and return an error card
+Widget buildErrorCard(String message) {
+  return Card(
+    elevation: 2.0,
+    color: Colors.red,
+    child: Padding(
+      padding: const EdgeInsets.all(8.0),
+      child: Row(
+        children: <Widget>[
+          Padding(
+            padding: const EdgeInsets.only(right: 8.0),
+            child: Icon(
+              Icons.error,
+              color: Colors.white,
+            ),
+          ),
+          Flexible(
+            child: Text(
+              message,
+              style: TextStyle(color: Colors.white),
+              maxLines: null,
+            ),
+          )
+        ],
+      ),
+    ),
+  );
+}