Начал добавлять запросы на регистрацию, валидацию, удаление токена кассы

lib/registration.dart

@@ -10,14 +10,15 @@ class RegistrationScreen extends StatefulWidget {
 
 class _RegistrationScreenState extends BaseState<RegistrationScreen> {
 
-  static const platform = const MethodChannel('com.dinnect.checker/scanner');
+  static const platform = const MethodChannel('com.dinnect.checker');
+
+  String _merchantID = "";
+  String _posNumber = "";
 
   @override Widget build(BuildContext context) {
     return new Scaffold(appBar: _getAppBar(), body: _getScreen());
   }
 
-  faq() {}
-
   AppBar _getAppBar() {
     return new AppBar(title: new Text("Регистрация магазина"),
         backgroundColor: const Color(0xff4272e7),  actions: <Widget>[
@@ -77,7 +78,15 @@ class _RegistrationScreenState extends BaseState<RegistrationScreen> {
     return new TextField(decoration: new InputDecoration(hintText: hint,
         hideDivider: true,
         hintStyle: new TextStyle(color: const Color(0xffa5a5a5),
-            fontSize: 16.0)));
+            fontSize: 16.0)), onChanged: (text) => _handleUserInput(text) );
+  }
+
+  void _handleUserInput(String text) {
+    if (text.length > 0) {
+      setState(() {                                                  //new
+        _merchantID = text;
+      });
+    }
   }
 
   Decoration _getDecoraionForInputField() {
@@ -92,9 +101,31 @@ class _RegistrationScreenState extends BaseState<RegistrationScreen> {
         child: new Container(height: 64.0, padding: new EdgeInsets.all(8.0),
             child: new RaisedButton(child: new Text('ЗАРЕГИСТРИРОВАТЬ',
                 style: new TextStyle(color: Colors.white)),
-                onPressed: null, disabledColor: const Color(0xffbfbfbf))));
+                onPressed: _merchantID.length == 0
+                ? null
+                : () => _register(_merchantID),
+                disabledColor: const Color(0xffbfbfbf))));
   }
 
-  doStuff() {}
+  void _register(String merchantShop) {
+    _registerToken(merchantShop);
+  }
 
+  Future<Null> _registerToken(String merchantShop) async {
+
+    String pos = await platform.invokeMethod('getInstanceID');
+    String userAgent = 'dm-checker-test v1.0.1';
+
+    var body = {
+      'merchant_shop' : merchantShop,
+      'pos' : pos,
+      'description' : userAgent + '-' + pos
+    };
+
+    httpClient.post(intUrl, body: body).then((response) {
+      print(response);
+    }).catchError((error) {
+      print(error);
+    });
+  }
 }