自己实现

lib/bloc/counter_bloc.dart

+import 'package:bloc/bloc.dart';
+import 'package:counter/bloc/counter_event.dart';
+
+class CounterBloc extends Bloc<CounterEvent,int> {
+  @override
+  int get initialState => 0;
+
+  @override
+  Stream<int> mapEventToState(CounterEvent event) async* {
+    switch (event) {
+      case CounterEvent.increment:
+        int s = currentState + 1;
+        print(s);
+        yield s;
+        break;
+      case CounterEvent.decrement:
+      int s = currentState - 1;
+        print(s);
+        yield s;
+        break;
+    }
+  }
+
+}
\ No newline at end of file

lib/bloc/counter_event.dart

+enum CounterEvent{
+  increment,
+  decrement
+}
\ No newline at end of file

lib/main.dart

+import 'package:counter/bloc/counter_bloc.dart';
+import 'package:counter/view/counter_page.dart';
 import 'package:flutter/material.dart';
+import 'package:flutter_bloc/flutter_bloc.dart';
 
 void main() => runApp(MyApp());
 
 class MyApp extends StatelessWidget {
-  // This widget is the root of your application.
   @override
   Widget build(BuildContext context) {
     return MaterialApp(
       title: 'Flutter Demo',
       theme: ThemeData(
-        // This is the theme of your application.
-        //
-        // Try running your application with "flutter run". You'll see the
-        // application has a blue toolbar. Then, without quitting the app, try
-        // changing the primarySwatch below to Colors.green and then invoke
-        // "hot reload" (press "r" in the console where you ran "flutter run",
-        // or simply save your changes to "hot reload" in a Flutter IDE).
-        // Notice that the counter didn't reset back to zero; the application
-        // is not restarted.
         primarySwatch: Colors.blue,
       ),
-      home: MyHomePage(title: 'Flutter Demo Home Page'),
-    );
-  }
-}
-
-class MyHomePage extends StatefulWidget {
-  MyHomePage({Key key, this.title}) : super(key: key);
-
-  // This widget is the home page of your application. It is stateful, meaning
-  // that it has a State object (defined below) that contains fields that affect
-  // how it looks.
-
-  // This class is the configuration for the state. It holds the values (in this
-  // case the title) provided by the parent (in this case the App widget) and
-  // used by the build method of the State. Fields in a Widget subclass are
-  // always marked "final".
-
-  final String title;
-
-  @override
-  _MyHomePageState createState() => _MyHomePageState();
-}
-
-class _MyHomePageState extends State<MyHomePage> {
-  int _counter = 0;
-
-  void _incrementCounter() {
-    setState(() {
-      // This call to setState tells the Flutter framework that something has
-      // changed in this State, which causes it to rerun the build method below
-      // so that the display can reflect the updated values. If we changed
-      // _counter without calling setState(), then the build method would not be
-      // called again, and so nothing would appear to happen.
-      _counter++;
-    });
-  }
-
-  @override
-  Widget build(BuildContext context) {
-    // This method is rerun every time setState is called, for instance as done
-    // by the _incrementCounter method above.
-    //
-    // The Flutter framework has been optimized to make rerunning build methods
-    // fast, so that you can just rebuild anything that needs updating rather
-    // than having to individually change instances of widgets.
-    return Scaffold(
-      appBar: AppBar(
-        // Here we take the value from the MyHomePage object that was created by
-        // the App.build method, and use it to set our appbar title.
-        title: Text(widget.title),
-      ),
-      body: Center(
-        // Center is a layout widget. It takes a single child and positions it
-        // in the middle of the parent.
-        child: Column(
-          // Column is also a layout widget. It takes a list of children and
-          // arranges them vertically. By default, it sizes itself to fit its
-          // children horizontally, and tries to be as tall as its parent.
-          //
-          // Invoke "debug painting" (press "p" in the console, choose the
-          // "Toggle Debug Paint" action from the Flutter Inspector in Android
-          // Studio, or the "Toggle Debug Paint" command in Visual Studio Code)
-          // to see the wireframe for each widget.
-          //
-          // Column has various properties to control how it sizes itself and
-          // how it positions its children. Here we use mainAxisAlignment to
-          // center the children vertically; the main axis here is the vertical
-          // axis because Columns are vertical (the cross axis would be
-          // horizontal).
-          mainAxisAlignment: MainAxisAlignment.center,
-          children: <Widget>[
-            Text(
-              'You have pushed the button this many times:',
-            ),
-            Text(
-              '$_counter',
-              style: Theme.of(context).textTheme.display1,
-            ),
-          ],
-        ),
+      home: BlocProvider(
+        builder: (context) => CounterBloc(),
+        child: CounterPage(),
       ),
-      floatingActionButton: FloatingActionButton(
-        onPressed: _incrementCounter,
-        tooltip: 'Increment',
-        child: Icon(Icons.add),
-      ), // This trailing comma makes auto-formatting nicer for build methods.
     );
   }
 }

lib/view/counter_page.dart

+import 'package:counter/bloc/counter_bloc.dart';
+import 'package:counter/bloc/counter_event.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_bloc/flutter_bloc.dart';
+
+class CounterPage extends StatelessWidget {
+  @override
+  Widget build(BuildContext context) {
+    final CounterBloc _counterBloc = BlocProvider.of<CounterBloc>(context);
+    return Scaffold(
+      appBar: AppBar(
+        title: Text('计数器'),
+      ),
+      body: BlocBuilder<CounterBloc, int>(
+        bloc: _counterBloc,
+        builder: (BuildContext context, int count) {
+          return Center(
+            child: Column(
+              mainAxisAlignment: MainAxisAlignment.center,
+              children: <Widget>[
+                Text(
+                  'You have pushed the button this many times:',
+                ),
+                Text(
+                  '$count',
+                  style: Theme.of(context).textTheme.display1,
+                ),
+              ],
+            ),
+          );
+        },
+      ),
+      floatingActionButton: Column(
+        mainAxisAlignment: MainAxisAlignment.end,
+        crossAxisAlignment: CrossAxisAlignment.end,
+        children: <Widget>[
+          FloatingActionButton(
+            onPressed: () {
+              _counterBloc.dispatch(CounterEvent.increment);
+            },
+            tooltip: 'Increment',
+            child: Icon(Icons.add),
+          ),
+          FloatingActionButton(
+            onPressed: () {
+              _counterBloc.dispatch(CounterEvent.decrement);
+            },
+            tooltip: 'Decrement',
+            child: Icon(Icons.remove),
+            backgroundColor: Colors.red,
+          ),
+        ],
+      ), // This trailing comma makes auto-formatting nicer for build methods.
+    );
+  }
+}

pubspec.lock

@@ -8,6 +8,13 @@ packages:
       url: "https://pub.flutter-io.cn"
     source: hosted
     version: "2.2.0"
+  bloc:
+    dependency: transitive
+    description:
+      name: bloc
+      url: "https://pub.flutter-io.cn"
+    source: hosted
+    version: "0.14.4"
   boolean_selector:
     dependency: transitive
     description:
@@ -41,6 +48,13 @@ packages:
     description: flutter
     source: sdk
     version: "0.0.0"
+  flutter_bloc:
+    dependency: "direct main"
+    description:
+      name: flutter_bloc
+      url: "https://pub.flutter-io.cn"
+    source: hosted
+    version: "0.20.0"
   flutter_test:
     dependency: "direct dev"
     description: flutter
@@ -74,6 +88,13 @@ packages:
       url: "https://pub.flutter-io.cn"
     source: hosted
     version: "1.8.0+1"
+  provider:
+    dependency: transitive
+    description:
+      name: provider
+      url: "https://pub.flutter-io.cn"
+    source: hosted
+    version: "3.0.0+1"
   quiver:
     dependency: transitive
     description:
@@ -81,6 +102,13 @@ packages:
       url: "https://pub.flutter-io.cn"
     source: hosted
     version: "2.0.3"
+  rxdart:
+    dependency: transitive
+    description:
+      name: rxdart
+      url: "https://pub.flutter-io.cn"
+    source: hosted
+    version: "0.22.1+1"
   sky_engine:
     dependency: transitive
     description: flutter

pubspec.yaml

@@ -23,6 +23,7 @@ dependencies:
   # The following adds the Cupertino Icons font to your application.
   # Use with the CupertinoIcons class for iOS style icons.
   cupertino_icons: ^0.1.2
+  flutter_bloc:
 
 dev_dependencies:
   flutter_test: