Scroll to textfield on focus

lib/screens/registration.dart

@@ -22,6 +22,7 @@ class RegistrationScreen extends BaseScreen {
 class RegistrationScreenState extends BaseState<RegistrationScreen> {
 
   RegistrationScreenState(SqliteHelper helper, String app) : super(helper, app);
+  FocusNode _focusNode = new FocusNode();
 
   @override
   Widget build(BuildContext ctx) {
@@ -54,12 +55,15 @@ class RegistrationScreenState extends BaseState<RegistrationScreen> {
 
   @override
   getTextWidget() {
-    return new TextField(
+    return new EnsureVisibleWhenFocused(
+      focusNode: _focusNode,
+      child: new TextField(
+        focusNode: _focusNode,
         keyboardType: TextInputType.number,
         decoration: new InputDecoration.collapsed(
             hintText: getHintString(),
             hintStyle: new TextStyle(color: greyTextColor, fontSize: 16.0)),
-        onChanged: (text) => handleUserInput(text));
+        onChanged: (text) => handleUserInput(text)));
   }
 
   /// Возвращает кнопку регистрации.