Камера не падает, проверка интернет соединения в условиях отсутствия интернета, буквенная клавиатура на вводе суммы

lib/purchase.dart

@@ -2,6 +2,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 import 'dart:convert';
 import 'dart:async';
+import 'dart:core';
 
 import 'main.dart';
 import 'common.dart';
@@ -23,9 +24,12 @@ class PurchaseScreen extends StatefulWidget {
 
 class PurchaseScreenState<T> extends BaseState<PurchaseScreen> {
 
+  RegExp exp;
+
   PurchaseScreenState(String userString, String card) {
     this.user = JSON.decode(userString);
     this.card = card;
+    exp = new RegExp(r'''^(?!0\.00)\d{1,11}(\.\d{0,2})?$''');
     getLoyality(user['loyalty_url']);
   }
 
@@ -65,30 +69,36 @@ class PurchaseScreenState<T> extends BaseState<PurchaseScreen> {
 
   /// Смена состояния экрана при изменении текста в поле ввода.
   @override handleUserInput(String tmpString) {
+
     setState(() {
-      double.parse(tmpString);
-      tmpString = tmpString.replaceAll('-', '');
-      tmpString = tmpString.replaceAll(',', '');
-      print(tmpString);
-      if (tmpString.contains('.')) {
-        int dotIndex = tmpString.indexOf('.');
-        integerPart = tmpString.substring(0, dotIndex);
-        fractionalPart = tmpString.substring(dotIndex + 1, tmpString.length);
-        if (fractionalPart.length > 2) {
-          fractionalPart = fractionalPart.substring(0, 2);
+
+      if (tmpString.length == 0 || exp.hasMatch(tmpString)) {
+        if (tmpString.contains('.')) {
+          int dotIndex = tmpString.indexOf('.');
+          integerPart = tmpString.substring(0, dotIndex);
+          fractionalPart = tmpString.substring(dotIndex + 1, tmpString.length);
+          if (fractionalPart.length > 2) {
+            fractionalPart = fractionalPart.substring(0, 2);
+          }
+          controller.text = '${integerPart}.${fractionalPart}';
+        } else {
+          integerPart = tmpString;
+          controller.text = tmpString;
         }
-        controller.text = '${integerPart}.${fractionalPart}';
+        textFieldValue = tmpString;
+
       } else {
-        integerPart = tmpString;
-        controller.text = tmpString;
+        tmpString = tmpString.substring(0, tmpString.length - 1);
+        controller.text = tmpString.replaceAll('a', '');
+        textFieldValue = tmpString;
       }
-      textFieldValue = tmpString;
     });
   }
 
   @override getTextWidget() {
-    return new TextField(decoration: new InputDecoration.collapsed(hintText: getHint(),
+    return new TextField(keyboardType: TextInputType.text, decoration: new InputDecoration.collapsed(hintText: getHint(),
       hintStyle: new TextStyle(color: greyTextColor, fontSize: 16.0)),
+      controller: controller,
       onChanged: (text) => handleUserInput(text));
   }
 
@@ -136,6 +146,10 @@ class PurchaseScreenState<T> extends BaseState<PurchaseScreen> {
       temporaryFractional = temporaryFractional + '0';
     }
 
+    if (temporaryInteger.length == 0) {
+      temporaryInteger = '0';
+    }
+
     return temporaryInteger + '.' + temporaryFractional;
   }