1、兼容网络请求-响应数据返回string类型；

lib/utils/utils.dart

+import 'dart:convert';
+
 import 'package:apk_update/utils/toast_util.dart';
 import 'package:apk_update/widget/update_dialog.dart';
 import 'package:dio/dio.dart';
@@ -45,6 +47,10 @@ void checkVersion({
         "queryParameters：${requestOptions.queryParameters}\n"
         "headers：${headers.map}\n\n"
         "responseData：$responseData\n");
+    if (responseData.runtimeType == String) {
+      // 兼容后端数据返回string
+      responseData = json.decode(responseData);
+    }
     if (responseData?["code"] != 0) {
       ToastUtil.showToast(responseData?["msg"]);
       return;