Bug fix callJsMethod: Encode/decode JSON when passing data between languages

lib/src/controller/impl/mobile.dart

@@ -1,4 +1,6 @@
 import 'dart:async' show Future;
+import 'dart:convert';
+import 'dart:io';
 
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart' show rootBundle;
@@ -127,9 +129,17 @@ class WebViewXController extends ChangeNotifier
 
     // (MOBILE ONLY) Unquotes response if necessary
     //
-    // In the mobile version responses from Js to Dart come wrapped in single quotes (')
-    // The web works fine because it is already into it's native environment
-    return HtmlUtils.unQuoteJsResponseIfNeeded(result);
+    // The web works fine because it is already into its native environment
+    // but on mobile we need to parse the result
+    if (Platform.isAndroid) {
+      // On Android `result` will be JSON, so we decode it
+      return json.decode(result);
+    } else {
+      /// TODO: make sure this works on iOS
+      // In the iOS version responses from JS to Dart come wrapped in single quotes (')
+      // Note that the supported types are more limited because of connector.evaluateJavascript
+      return HtmlUtils.unQuoteJsResponseIfNeeded(result);
+    }
   }
 
   /// This function allows you to evaluate 'raw' javascript (e.g: 2+2)

lib/src/utils/html_utils.dart

@@ -134,7 +134,10 @@ class HtmlUtils {
     }
 
     for (final param in params) {
-      args.write(addSingleQuotes(param.toString()));
+      // Encode JSON from param
+      // For example, strings will be encoded so JavaScript reads them exactly
+      // as on Dart
+      args.write(json.encode(param));
       args.write(',');
     }
 
@@ -144,11 +147,6 @@ class HtmlUtils {
     return function;
   }
 
-  /// Adds single quotes to the param
-  static String addSingleQuotes(String data) {
-    return "'$data'";
-  }
-
   /// Embeds js in the HTML source at the specified position
   /// This is just a helper function for the generic [embedInHtmlSource] function
   static String embedJsInHtmlSource(