Сделал возможность переключаться между приложениями и добавлять новые приложения практически не меняя код

lib/purchase.dart

@@ -3,12 +3,13 @@ import 'package:flutter/services.dart';
 import 'dart:convert';
 import 'dart:core';
 
-import 'package:checker/strings.dart';
-import 'package:checker/common.dart';
-import 'package:checker/consts.dart';
-import 'package:checker/network.dart';
-import 'package:checker/base_state.dart';
-import 'package:checker/purchase_success.dart';
+import 'resources.dart';
+import 'strings.dart';
+import 'common.dart';
+import 'consts.dart';
+import 'network.dart';
+import 'base_state.dart';
+import 'purchase_success.dart';
 
 /// Экран проведения покупки.
 class PurchaseScreen extends StatefulWidget {
@@ -41,15 +42,15 @@ class PurchaseScreenState<T> extends BaseState<PurchaseScreen> {
 
   @override Widget getScreenContent() {
     return new Column(
-      children: <Widget>[new Expanded(child: new ListView(children: <Widget>[
-        getValueWithDescription(StringsLocalization.userName(), user['first_name'] == null ? '' : user['first_name']),
-        getValueWithDescription(StringsLocalization.card(), card),
-        getValueWithDescription(StringsLocalization.reward(), loyalty),
-        getHintLabel(),
-        getInputField(),
-        wrapButton(getScreenMargins(36.0), getCompleteButton()),
-        wrapButton(getScreenMargins(24.0), getScanButton(context, StringsLocalization.scan(), primaryColor))
-      ]))]);
+        children: <Widget>[new Expanded(child: new ListView(children: <Widget>[
+          getValueWithDescription(StringsLocalization.userName(), user['first_name'] == null ? '' : user['first_name']),
+          getValueWithDescription(StringsLocalization.card(), card),
+          getValueWithDescription(StringsLocalization.reward(), loyalty),
+          getHintLabel(),
+          getInputField(),
+          wrapButton(getScreenMargins(36.0), getCompleteButton()),
+          wrapButton(getScreenMargins(24.0), getScanButton(context, StringsLocalization.scan(), Resources.getPrimaryColor(app)))
+        ]))]);
   }
 
   getScreenMargins(double top) {
@@ -62,16 +63,16 @@ class PurchaseScreenState<T> extends BaseState<PurchaseScreen> {
   }
 
   Widget getScanButton(BuildContext context, String title, Color textColor) {
-    return new Container(height: buttonHeight, child: new FlatButton(child: new Text(title,
-        style: new TextStyle(color: textColor)),
-        onPressed: () => startScanner(context)),
-        decoration: getDecorationForScanButton());
-  }
-
-  getDecorationForScanButton() {
-    return new BoxDecoration(
-        border: new Border.all(color: buttonColor, width: 1.0),
-        borderRadius: new BorderRadius.all(new Radius.circular(4.0)));
+    return new Container(
+        height: buttonHeight,
+        child: new FlatButton(
+            child: new Text(
+                title,
+                style: new TextStyle(color: textColor)),
+            onPressed: () => startScanner(context, app)),
+        decoration: new BoxDecoration(
+            border: new Border.all(color: Resources.getButtonColor(app), width: 1.0),
+            borderRadius: new BorderRadius.all(new Radius.circular(4.0))));
   }
 
   @override String getTitle() {
@@ -88,19 +89,19 @@ class PurchaseScreenState<T> extends BaseState<PurchaseScreen> {
 
   @override getTextWidget() {
     return new TextField(
-        keyboardType: TextInputType.number,
-        decoration: new InputDecoration.collapsed(
+      keyboardType: TextInputType.number,
+      decoration: new InputDecoration.collapsed(
           hintText: getHint(),
           hintStyle: new TextStyle(color: greyTextColor, fontSize: 16.0)
-        ),
-        controller: controller,
-        onSubmitted: (String text) {
-          setState(() {
-            controller.text = _parseSum(text);
-          });
-        },
-        textAlign: TextAlign.center,
-        autofocus: true,
+      ),
+      controller: controller,
+      onSubmitted: (String text) {
+        setState(() {
+          controller.text = _parseSum(text);
+        });
+      },
+      textAlign: TextAlign.center,
+      autofocus: true,
     );
   }
 
@@ -138,10 +139,10 @@ class PurchaseScreenState<T> extends BaseState<PurchaseScreen> {
 
   String _cleanupNumber(String text){
     String tmp = text
-      .replaceAll(' ', '')
-      .replaceAll('-', '')
-      .replaceAll(',', '.')
-      .replaceAll('..', '.');
+        .replaceAll(' ', '')
+        .replaceAll('-', '')
+        .replaceAll(',', '.')
+        .replaceAll('..', '.');
 
     while(tmp.indexOf('..') != -1){
       tmp = tmp.replaceAll('..', '.');
@@ -175,22 +176,22 @@ class PurchaseScreenState<T> extends BaseState<PurchaseScreen> {
   onPurchaseClick() {
     String val = _parseSum(controller.text);
     showDialog(context: context, child: new AlertDialog(
-      title: new Text(StringsLocalization.confirmation()),
-      content: new Text(StringsLocalization.confirmPurchase(val)),
-      actions: <Widget>[
-        new FlatButton(
-          child: new Text(StringsLocalization.no()),
-          onPressed: () {
-            Navigator.of(context).pop();
-          },
-        ),
-        new FlatButton(
-          child: new Text(StringsLocalization.yes()),
-          onPressed: () {
-            purchase(val);
-          },
-        )
-      ]));
+        title: new Text(StringsLocalization.confirmation()),
+        content: new Text(StringsLocalization.confirmPurchase(val)),
+        actions: <Widget>[
+          new FlatButton(
+            child: new Text(StringsLocalization.no()),
+            onPressed: () {
+              Navigator.of(context).pop();
+            },
+          ),
+          new FlatButton(
+            child: new Text(StringsLocalization.yes()),
+            onPressed: () {
+              purchase(val);
+            },
+          )
+        ]));
   }
 
   purchase(String sumTotal) async {
@@ -201,30 +202,30 @@ class PurchaseScreenState<T> extends BaseState<PurchaseScreen> {
         String token = await platform.invokeMethod('getToken');
         platform.invokeMethod('getDocID').then((result) {
 
-            String url = user['purchases_url'];
+          String url = user['purchases_url'];
 
-            var body = {
-              'doc_id': result,
-              'curr_iso_code': '643',
-              'commit': 'true',
-              'sum_total': sumTotal
-            };
+          var body = {
+            'doc_id': result,
+            'curr_iso_code': '643',
+            'commit': 'true',
+            'sum_total': sumTotal
+          };
 
-            var headers = {
-              'DM-Authorization': 'dmapptoken $appToken',
-              'Authorization': 'dmtoken ${token}'
-            };
+          var headers = {
+            'DM-Authorization': 'dmapptoken $appToken',
+            'Authorization': 'dmtoken ${token}'
+          };
 
-            httpClient.post(url, body: body, headers: headers).then((response) {
+          httpClient.post(url, body: body, headers: headers).then((response) {
 
-              print(response.body);
-              Navigator.of(context).pop();
-              pushRoute(context, new PurchaseSuccessScreen(sumTotal, user['first_name'] == null ? '' : user['first_name']));
+            print(response.body);
+            Navigator.of(context).pop();
+            pushRoute(context, new PurchaseSuccessScreen(sumTotal, user['first_name'] == null ? '' : user['first_name']));
 
-            }).catchError((error) {
-              purchaseInProgress = false;
-              print(error.toString());
-            });
+          }).catchError((error) {
+            purchaseInProgress = false;
+            print(error.toString());
+          });
         });
       }
     }