update provider example

adding addAll use case

Author: Vadaski

mecury_project/example/provider_example/lib/goods_model.dart

@@ -1,6 +1,9 @@
 import 'package:flutter/material.dart' show ChangeNotifier;
 
 class GoodsListProvider with ChangeNotifier {
+
+  bool shouldRebuild = false;
+
   List<Goods> _goodsList =
       List.generate(10, (index) => Goods(false, 'Goods No. $index'));
 
@@ -12,6 +15,16 @@ class GoodsListProvider with ChangeNotifier {
     _goodsList[index] = Goods(!good.isCollection, good.goodsName);
     notifyListeners();
   }
+
+  addAll(){
+    _goodsList.addAll(List.generate(10, (index)=>Goods(false, 'Goods No. $index')));
+    shouldRebuild = true;
+    notifyListeners();
+  }
+
+  rebuild(){
+    shouldRebuild = false;
+  }
 }
 
 class Goods {

mecury_project/example/provider_example/lib/screens.dart

@@ -152,31 +152,44 @@ class GoodsListScreen extends StatelessWidget {
   Widget build(BuildContext context) {
     return ChangeNotifierProvider(
       create: (_) => GoodsListProvider(),
-      child: Selector<GoodsListProvider, GoodsListProvider>(
-        shouldRebuild: (pre, next) => false,
-        selector: (context, provider) => provider,
-        builder: (context, provider, child) {
-          return ListView.builder(
-            itemCount: provider.total,
-            itemBuilder: (context, index) {
-              return Selector<GoodsListProvider, Goods>(
-                selector: (context, provider) => provider.goodsList[index],
-                builder: (context, data, child) {
-                  print(('No.${index + 1} rebuild'));
+      child: Scaffold(
+        body: Selector<GoodsListProvider, GoodsListProvider>(
+          shouldRebuild: (pre, next) => pre.shouldRebuild,
+          selector: (context, provider) => provider,
+          builder: (context, provider, child) {
+            provider.rebuild();
+            return ListView.builder(
+              itemCount: provider.total,
+              itemBuilder: (context, index) {
+                return Selector<GoodsListProvider, Goods>(
+                  selector: (context, provider) => provider.goodsList[index],
+                  builder: (context, data, child) {
+                    print(('No.${index + 1} rebuild'));
 
-                  return ListTile(
-                    title: Text(data.goodsName),
-                    trailing: GestureDetector(
-                      onTap: () => provider.collect(index),
-                      child: Icon(
-                          data.isCollection ? Icons.star : Icons.star_border),
-                    ),
-                  );
-                },
-              );
-            },
-          );
-        },
+                    return ListTile(
+                      title: Text(data.goodsName),
+                      trailing: GestureDetector(
+                        onTap: () => provider.collect(index),
+                        child: Icon(
+                            data.isCollection ? Icons.star : Icons.star_border),
+                      ),
+                    );
+                  },
+                );
+              },
+            );
+          },
+        ),
+        floatingActionButton: Consumer<GoodsListProvider>(
+          builder: (context, GoodsListProvider model, child) {
+            return FloatingActionButton(
+              child: Icon(Icons.add),
+              onPressed: () {
+                model.addAll();
+              },
+            );
+          },
+        ),
       ),
     );
   }