Flutter调用Firebase可调用函数报错：Response is not valid JSON object

我在给Flutter应用集成Firebase可调用函数时，一直遇到未处理异常：[firebase_functions/internal] Response is not valid JSON object，哪怕用最简化的测试函数也会出现同样问题。

云函数代码 #

const functions = require("firebase-functions");

exports.sendMessage = functions.https.onCall((data, context) => {
  return ["Apple", "Banana", "Cherry", "Date"];
});

Flutter端调用代码 #

Future<void> checkCallable() async {
    debugPrint((await FirebaseFunctions.instance.httpsCallable('sendMessage').call()).data);
}

错误信息 #

E/flutter (26536): [ERROR:flutter/lib/ui/ui_dart_state.cc(198)] Unhandled Exception: [firebase_functions/internal] Response is not valid JSON object.
E/flutter (26536): 
E/flutter (26536): #0      StandardMethodCodec.decodeEnvelope (package:flutter/src/services/message_codecs.dart:607:7)
E/flutter (26536): #1      MethodChannel._invokeMethod (package:flutter/src/services/platform_channel.dart:167:18)
E/flutter (26536): <asynchronous suspension>
E/flutter (26536): #2      MethodChannelHttpsCallable.call (package:cloud_functions_platform_interface/src/method_channel/method_channel_https_callable.dart:23:24)
E/flutter (26536): <asynchronous suspension>
E/flutter (26536): #3      HttpsCallable.call (package:cloud_functions/src/https_callable.dart:49:37)
E/flutter (26536): <asynchronous suspension>
E/flutter (26536): #4      _MyHomePageState.checkCallable (package:league_tracker/main.dart:79:17)
E/flutter (26536): <asynchronous suspension>
E/flutter (26536): 
E/flutter (26536): #0      StandardMethodCodec.decodeEnvelope (package:flutter/src/services/message_codecs.dart:607:7)
E/flutter (26536): #1      MethodChannel._invokeMethod (package:flutter/src/services/platform_channel.dart:167:18)
E/flutter (26536): <asynchronous suspension>
E/flutter (26536): #2      MethodChannelHttpsCallable.call (package:cloud_functions_platform_interface/src/method_channel/method_channel_https_callable.dart:23:24)
E/flutter (26536): <asynchronous suspension>
E/flutter (26536): #3      HttpsCallable.call (package:cloud_functions/src/https_callable.dart:49:37)
E/flutter (26536): <asynchronous suspension>
E/flutter (26536): #4      _MyHomePageState.checkCallable (package:league_tracker/main.dart:79:17)
E/flutter (26536): <asynchronous suspension>
E/flutter (26536): 
I/flutter (26536): Got null accent color.
D/InputTransport(26536): Input channel destroyed: 'ClientS', fd=146
E/flutter (26536): [ERROR:flutter/shell/common/shell.cc(93)] Dart Unhandled Exception: [firebase_functions/internal] Response is not valid JSON object.
E/flutter (26536): 
E/flutter (26536): #0      StandardMethodCodec.decodeEnvelope (package:flutter/src/services/message_codecs.dart:607:7)
E/flutter (26536): #1      MethodChannel._invokeMethod (package:flutter/src/services/platform_channel.dart:167:18)
E/flutter (26536): <asynchronous suspension>
E/flutter (26536): #2      MethodChannelHttpsCallable.call (package:cloud_functions_platform_interface/src/method_channel/method_channel_https_callable.dart:23:24)
E/flutter (26536): <asynchronous suspension>
E/flutter (26536): #3      HttpsCallable.call (package:cloud_functions/src/https_callable.dart:49:37)
E/flutter (26536): <asynchronous suspension>
E/flutter (26536): #4      _MyHomePageState.checkCallable (package:league_tracker/main.dart:79:17)
E/flutter (26536): <asynchronous suspension>
E/flutter (26536): , stack trace: #0      StandardMethodCodec.decodeEnvelope (package:flutter/src/services/message_codecs.dart:607:7)
E/flutter (26536): #1      MethodChannel._invokeMethod (package:flutter/src/services/platform_channel.dart:167:18)
E/flutter (26536): <asynchronous suspension>
E/flutter (26536): #2      MethodChannelHttpsCallable.call (package:cloud_functions_platform_interface/src/method_channel/method_channel_https_callable.dart:23:24)
E/flutter (26536): <asynchronous suspension>
E/flutter (26536): #3      HttpsCallable.call (package:cloud_functions/src/https_callable.dart:49:37)
E/flutter (26536): <asynchronous suspension>
E/flutter (26536): #4      _MyHomePageState.checkCallable (package:league_tracker/main.dart:79:17)
E/flutter (26536): <asynchronous suspension>
E/flutter (26536): 

补充尝试 #

我还试过返回以下内容，问题依旧：

return {message: text};

或者

return "text";

这个问题通常和返回值格式无关，主要排查以下几个方向：

1. 云函数部署状态

   • 确认执行firebase deploy --only functions完成部署，控制台显示部署成功。
   • 核对本地代码和云端代码是否一致，避免本地修改后未部署导致版本不匹配。

2. Flutter端Firebase配置

   • 确保google-services.json（Android）或GoogleService-Info.plist（iOS）是从Firebase控制台下载的最新文件。
   • 如果函数使用了非默认区域，调用时必须指定对应区域：

     FirebaseFunctions.instanceFor(region: 'us-central1') // 替换为你的函数实际区域
         .httpsCallable('sendMessage')
         .call();
     

     区域不匹配会导致请求指向错误地址，返回非JSON内容。

3. 云函数运行日志

   • 前往Firebase控制台的云函数页面，查看函数执行日志，确认函数是否正常执行并返回预期内容。如果函数内部抛出未捕获异常，会返回错误页面而非合法JSON。
   • 直接在控制台测试函数，验证返回值是否符合要求。

4. 网络环境

   • 确保测试设备能正常访问Firebase服务，避免代理篡改请求内容。
   • 切换网络（如WiFi换移动数据），排除网络环境干扰。

若以上都没问题，可尝试重置依赖：

• 删除Flutter项目的pubspec.lock，执行flutter pub get重新安装依赖。
• 重新部署云函数，确保云端环境干净。

内容的提问来源于stack exchange，提问作者Zan