Add Flutter GUI example for VAD with a microphone. (#905)

sherpa-onnx/flutter/example/lib/main.dart

@@ -4,6 +4,8 @@ import 'package:flutter/material.dart';
 
 import "./speaker_identification_test.dart";
 import "./vad_test.dart";
+import './home.dart';
+import './info.dart';
 
 void main() {
   runApp(const MyApp());
@@ -11,110 +13,56 @@ void main() {
 
 class MyApp extends StatelessWidget {
   const MyApp({Key? key}) : super(key: key);
-  // This widget is the root of your application.
   @override
   Widget build(BuildContext context) {
     return MaterialApp(
-      title: 'Flutter Demo',
+      title: 'Next-gen Kaldi',
       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'),
+      home: const MyHomePage(title: 'Next-gen Kaldi: VAD demo'),
     );
   }
 }
 
 class MyHomePage extends StatefulWidget {
   const MyHomePage({Key? key, required 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
   State<MyHomePage> createState() => _MyHomePageState();
 }
 
 class _MyHomePageState extends State<MyHomePage> {
-  int _counter = 0;
-  Future<void> _incrementCounter() async {
-    if (_counter <= 10) {
-      sherpa_onnx.initBindings();
-      await testSpeakerID();
-      // await testVad();
-    }
-
-    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++;
-    });
-  }
-
+  int _currentIndex = 0;
+  final List<Widget> _tabs = [
+    HomeScreen(),
+    InfoScreen(),
+  ];
   @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.headlineSmall,
-            ),
-          ],
-        ),
+      body: _tabs[_currentIndex],
+      bottomNavigationBar: BottomNavigationBar(
+        currentIndex: _currentIndex,
+        onTap: (int index) {
+          setState(() {
+            _currentIndex = index;
+          });
+        },
+        items: [
+          BottomNavigationBarItem(
+            icon: Icon(Icons.home),
+            label: 'Home',
+          ),
+          BottomNavigationBarItem(
+            icon: Icon(Icons.info),
+            label: 'Info',
+          ),
+        ],
       ),
-      floatingActionButton: FloatingActionButton(
-        onPressed: _incrementCounter,
-        tooltip: 'Increment',
-        child: const Icon(Icons.add),
-      ), // This trailing comma makes auto-formatting nicer for build methods.
     );
   }
 }