From c6f1d7182a87b3d837c08bc69443a0c9cee8b7e5 Mon Sep 17 00:00:00 2001
From: Herwig Birke <Herwig.Birke@windesign.at>
Date: Thu, 28 Mar 2024 08:46:19 +0100
Subject: [PATCH] FutureBuilder

---
 lib/widgets/grocery_list.dart | 138 ++++++++++++++++------------------
 1 file changed, 63 insertions(+), 75 deletions(-)

diff --git a/lib/widgets/grocery_list.dart b/lib/widgets/grocery_list.dart
index 68ad7c4..d6af5ba 100644
--- a/lib/widgets/grocery_list.dart
+++ b/lib/widgets/grocery_list.dart
@@ -16,59 +16,44 @@ class GroceryList extends StatefulWidget {
 
 class _GroceryListState extends State<GroceryList> {
   List<GroceryItem> _groceryItems = [];
-  var _isLoading = true;
+  late Future<List<GroceryItem>> _loadedItems;
   String? _error;
 
   @override
   void initState() {
     super.initState();
-    _loadItems();
+    _loadedItems = _loadItems();
   }
 
-  void _loadItems() async {
+  Future<List<GroceryItem>> _loadItems() async {
     final url = Uri.https(
         'flutter-prep-dccfe-default-rtdb.firebaseio.com', 'shopping-list.json');
 
-    try {
-      final response = await http.get(url);
+    final response = await http.get(url);
 
-      if (response.statusCode >= 400) {
-        setState(() {
-          _error = 'Failed to fetch data. Please try again later.';
-        });
-      }
-
-      if (response.body == 'null') {
-        setState(() {
-          _isLoading = false;
-        });
-        return;
-      }
-
-      final Map<String, dynamic> listData = json.decode(response.body);
-      final List<GroceryItem> loadedItems = [];
-      for (final item in listData.entries) {
-        final category = categories.entries
-            .firstWhere(
-                (catItem) => catItem.value.title == item.value['category'])
-            .value;
-        loadedItems.add(GroceryItem(
-          id: item.key,
-          name: item.value['name'],
-          quantity: item.value['quantity'],
-          category: category,
-        ));
-      }
-
-      setState(() {
-        _groceryItems = loadedItems;
-        _isLoading = false;
-      });
-    } catch (error) {
-      setState(() {
-        _error = 'Something went wrong. Please try again later.';
-      });
+    if (response.statusCode >= 400) {
+      throw Exception('Failed to fetch grocery items. Please try again later.');
     }
+
+    if (response.body == 'null') {
+      return [];
+    }
+
+    final Map<String, dynamic> listData = json.decode(response.body);
+    final List<GroceryItem> loadedItems = [];
+    for (final item in listData.entries) {
+      final category = categories.entries
+          .firstWhere(
+              (catItem) => catItem.value.title == item.value['category'])
+          .value;
+      loadedItems.add(GroceryItem(
+        id: item.key,
+        name: item.value['name'],
+        quantity: item.value['quantity'],
+        category: category,
+      ));
+    }
+    return loadedItems;
   }
 
   void _addItem() async {
@@ -107,39 +92,6 @@ class _GroceryListState extends State<GroceryList> {
 
   @override
   Widget build(BuildContext context) {
-    Widget content = const Center(child: Text('No items added yet.'));
-
-    if (_isLoading) {
-      content = const Center(child: CircularProgressIndicator());
-    }
-
-    if (_groceryItems.isNotEmpty) {
-      content = ListView.builder(
-        itemCount: _groceryItems.length,
-        itemBuilder: (ctx, index) => Dismissible(
-          onDismissed: (direction) {
-            _removeItem(_groceryItems[index]);
-          },
-          key: ValueKey(_groceryItems[index].id),
-          child: ListTile(
-            title: Text(_groceryItems[index].name),
-            leading: Container(
-              width: 24,
-              height: 24,
-              color: _groceryItems[index].category.color,
-            ),
-            trailing: Text(
-              _groceryItems[index].quantity.toString(),
-            ),
-          ),
-        ),
-      );
-    }
-
-    if (_error != null) {
-      content = Center(child: Text(_error!));
-    }
-
     return Scaffold(
       appBar: AppBar(
         title: const Text('Your Groceries'),
@@ -150,7 +102,43 @@ class _GroceryListState extends State<GroceryList> {
           ),
         ],
       ),
-      body: content,
+      body: FutureBuilder(
+        future: _loadedItems,
+        builder: (context, snapshot) {
+          if (snapshot.connectionState == ConnectionState.waiting) {
+            return const Center(child: CircularProgressIndicator());
+          }
+
+          if (snapshot.hasError) {
+            return Center(child: Text(snapshot.error.toString()));
+          }
+
+          if (snapshot.data!.isEmpty) {
+            return const Center(child: Text('No items added yet.'));
+          }
+
+          return ListView.builder(
+            itemCount: snapshot.data!.length,
+            itemBuilder: (ctx, index) => Dismissible(
+              onDismissed: (direction) {
+                _removeItem(snapshot.data![index]);
+              },
+              key: ValueKey(snapshot.data![index].id),
+              child: ListTile(
+                title: Text(snapshot.data![index].name),
+                leading: Container(
+                  width: 24,
+                  height: 24,
+                  color: snapshot.data![index].category.color,
+                ),
+                trailing: Text(
+                  snapshot.data![index].quantity.toString(),
+                ),
+              ),
+            ),
+          );
+        },
+      ),
     );
   }
 }