feat: Using MobX state management

lib/main.dart

@@ -1,115 +1,15 @@
 import 'package:flutter/material.dart';
-
-void main() {
-  runApp(const MyApp());
-}
-
+import 'package:language/pages/counter_page.dart';
+
+void main() => runApp(const MyApp());
+
 class MyApp extends StatelessWidget {
   const MyApp({super.key});
 
-  // 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: const MyHomePage(title: 'Flutter Demo Home Page'),
-    );
-  }
-}
-
-class MyHomePage extends StatefulWidget {
-  const MyHomePage({super.key, required this.title});
-
-  // 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
-  State<MyHomePage> 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>[
-            const Text(
-              'You have pushed the button this many times:',
-            ),
-            Text(
-              '$_counter',
-              style: Theme.of(context).textTheme.headlineMedium,
-            ),
-          ],
-        ),
-      ),
-      floatingActionButton: FloatingActionButton(
-        onPressed: _incrementCounter,
-        tooltip: 'Increment',
-        child: const Icon(Icons.add),
-      ), // This trailing comma makes auto-formatting nicer for build methods.
+      home: CounterPage(),
     );
   }
 }

lib/pages/counter_page.dart

@@ -0,0 +1,57 @@
+import 'package:language/store/counter/counter.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_mobx/flutter_mobx.dart';
+
+class CounterPage extends StatelessWidget {
+  final Counter counter = Counter();
+
+  CounterPage({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+        appBar: AppBar(
+          title: const Text('Flutter and MobX by think'),
+        ),
+        body: Center(
+          child: Column(
+            mainAxisAlignment: MainAxisAlignment.center,
+            children: <Widget>[
+              const Text(
+                'Counter',
+                style: TextStyle(fontSize: 30.0),
+              ),
+              // const Text(
+              //   '0',
+              //   style: TextStyle(fontSize: 42.0),
+              // ),
+              // 这里先不用Text而是包裹一个新的widget，然后这里需要一个observer widget
+              // 它不是可以直接使用的，因此我们需要导入它
+              Observer(
+                  builder: (_) => Text(
+                        '${counter.value}',
+                        style: const TextStyle(fontSize: 42.0),
+                      )),
+              // 现在我们有了Observe 和 builder，它随时给我们的Text一个最新的值
+              Row(
+                mainAxisAlignment: MainAxisAlignment.center,
+                children: <Widget>[
+                  TextButton.icon(
+                    icon: const Icon(Icons.add),
+                    label: const Text('Add'),
+                    // onPressed 回调可以用来调用counter.increment
+                    // onPressed: () {},
+                    onPressed: counter.increment,
+                  ),
+                  TextButton.icon(
+                    icon: const Icon(Icons.remove),
+                    label: const Text('Remove'),
+                    onPressed: counter.decrement,
+                  ),
+                ],
+              )
+            ],
+          ),
+        ));
+  }
+}

lib/store/counter/counter.dart

@@ -0,0 +1,24 @@
+import 'package:mobx/mobx.dart';
+
+// This is our generated file (we'll see this soon!)
+part 'counter.g.dart';
+
+// We expose this to be used throughout our project
+class Counter = _Counter with _$Counter;
+
+// Our store class
+abstract class _Counter with Store {
+  @observable
+  // 定义变量，它是一个能够被观察到int类型的count
+  int value = 1;
+
+  @action
+  void increment() {
+    value++;
+  }
+
+  @action
+  void decrement() {
+    value--;
+  }
+}