Начал разбираться с вызовом специфичной для андроида Activity

lib/main.dart

@@ -1,4 +1,7 @@
+import 'dart:async';
+
 import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
 
 const String _name = "Ivan Murashov";
 
@@ -18,6 +21,7 @@ class ChatScreen extends StatefulWidget {
 
 class ChatScreenState extends State<ChatScreen> {
 
+  static const platform = const MethodChannel('samples.flutter.io/battery');
   final List<ChatMessage> _messages = <ChatMessage>[];
   final TextEditingController _textController = new TextEditingController();
 
@@ -64,10 +68,19 @@ class ChatScreenState extends State<ChatScreen> {
                                         decoration: textField)),
       new Container(margin: new EdgeInsets.symmetric(horizontal: 4.0),
                     child: new IconButton(icon: new Icon(Icons.send),
-                    onPressed: () => _handleSubmitted(_textController.text)))
+                    onPressed: () => startScanner()))
+//                    onPressed: () => _handleSubmitted(_textController.text)))
     ]);
   }
 
+  Future<Null> startScanner() async {
+    try {
+      platform.invokeMethod('startScanner');
+    } on PlatformException catch (e) {
+
+    }
+  }
+
   void _handleSubmitted(String text) {
     _textController.clear();
     ChatMessage message = new ChatMessage(text);