我正在开发一个将 spring-boot 后端用于应用程序方法的应用程序，并且我正在使用 flutter 开发我的前端。我制作了我需要的前端页面，但我不确定如何从 flutter 到我的后端进行 HTTP 调用

我尝试查看与我正在做的类似的 youtube 视频和其他堆栈溢出问题，但我仍然无法弄清楚。

比如这是登录鉴权的后台代码

/**
     * Controller method that attempts to login
     * 
     * @param username
     * @param password
     * @return ResponseEntity
     */
    @GetMapping("/auth/{username}/{password}")
    public ResponseEntity login(@PathVariable("username") String username, @PathVariable("password") String password)
            throws Exception {
        // No exception thrown means the authentication succeeded
        try {
            authentication.login(username, password);
        } catch (Exception e) {
            return ResponseEntity.status(HttpStatus.BAD_REQUEST).body(new Response(false, e.getMessage()));
        }
        return ResponseEntity.status(HttpStatus.OK).body(new Response(true, "Login successful"));
    }

这就是我在 Flutter 中包含的内容

...
String url = 'http://localhost:8080/users/auth/{username}/{password}';

  Future<String> login() async {
    var response = await http.get(Uri.encodeFull(url), headers:{"Accept" : "application/json"});
    Navigator.of(context).pushNamed('/signup');
  }
...

...

child: MaterialButton(
        minWidth: MediaQuery.of(context).size.width,
        padding: EdgeInsets.fromLTRB(20.0, 15.0, 20.0, 15.0),
        onPressed: () {
          login();
        },
        child: Text("Login",
        textAlign: TextAlign.center,
        style: style.copyWith(
          color: Colors.white, fontWeight: FontWeight.bold)),
      ),

...

这是出现的错误

E/flutter ( 3945): [ERROR:flutter/lib/ui/ui_dart_state.cc(148)] Unhandled Exception: Invalid argument(s): No host specified in URI /auth/%7Busername%7D/%7Bpassword%7D
E/flutter ( 3945): #0      _HttpClient._openUrl (dart:_http/http_impl.dart:2117:9)
E/flutter ( 3945): #1      _HttpClient.openUrl (dart:_http/http_impl.dart:2043:7)
E/flutter ( 3945): #2      IOClient.send (package:http/src/io_client.dart:33:36)
E/flutter ( 3945): <asynchronous suspension>
E/flutter ( 3945): #3      BaseClient._sendUnstreamed (package:http/src/base_client.dart:169:38)
E/flutter ( 3945): <asynchronous suspension>
E/flutter ( 3945): #4      BaseClient.get (package:http/src/base_client.dart:32:7)
E/flutter ( 3945): #5      get.<anonymous closure> (package:http/http.dart:46:36)
E/flutter ( 3945): #6      _withClient (package:http/http.dart:166:20)
E/flutter ( 3945): <asynchronous suspension>
E/flutter ( 3945): #7      get (package:http/http.dart:46:5)
E/flutter ( 3945): #8      _MyHomePageState.login (package:calcount_mobile/main.dart:65:26)
E/flutter ( 3945): <asynchronous suspension>
E/flutter ( 3945): #9      _MyHomePageState.build.<anonymous closure> (package:calcount_mobile/main.dart:102:11)
E/flutter ( 3945): #10     _InkResponseState._handleTap (package:flutter/src/material/ink_well.dart:511:14)
E/flutter ( 3945): #11     _InkResponseState.build.<anonymous closure> (package:flutter/src/material/ink_well.dart:566:30)
E/flutter ( 3945): #12     GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:166:24)
E/flutter ( 3945): #13     TapGestureRecognizer._checkUp (package:flutter/src/gestures/tap.dart:240:9)
E/flutter ( 3945): #14     TapGestureRecognizer.handlePrimaryPointer (package:flutter/src/gestures/tap.dart:177:9)
E/flutter ( 3945): #15     PrimaryPointerGestureRecognizer.handleEvent (package:flutter/src/gestures/recognizer.dart:436:9)
E/flutter ( 3945): #16     PointerRouter._dispatch (package:flutter/src/gestures/pointer_router.dart:73:12)
E/flutter ( 3945): #17     PointerRouter.route (package:flutter/src/gestures/pointer_router.dart:101:11)
E/flutter ( 3945): #18     _WidgetsFlutterBinding&BindingBase&GestureBinding.handleEvent (package:flutter/src/gestures/binding.dart:221:19)
E/flutter ( 3945): #19     _WidgetsFlutterBinding&BindingBase&GestureBinding.dispatchEvent (package:flutter/src/gestures/binding.dart:199:22)
E/flutter ( 3945): #20     _WidgetsFlutterBinding&BindingBase&GestureBinding._handlePointerEvent (package:flutter/src/gestures/binding.dart:156:7)
E/flutter ( 3945): #21     _WidgetsFlutterBinding&BindingBase&GestureBinding._flushPointerEventQueue (package:flutter/src/gestures/binding.dart:102:7)
E/flutter ( 3945): #22     _WidgetsFlutterBinding&BindingBase&GestureBinding._handlePointerDataPacket (package:flutter/src/gestures/binding.dart:86:7)
E/flutter ( 3945): #23     _rootRunUnary (dart:async/zone.dart:1136:13)
E/flutter ( 3945): #24     _CustomZone.runUnary (dart:async/zone.dart:1029:19)
E/flutter ( 3945): #25     _CustomZone.runUnaryGuarded (dart:async/zone.dart:931:7)
E/flutter ( 3945): #26     _invoke1 (dart:ui/hooks.dart:233:10)
E/flutter ( 3945): #27     _dispatchPointerDataPacket (dart:ui/hooks.dart:154:5)
E/flutter ( 3945):

最佳答案

1. 如果您正在使用 flutter Emulator 设备测试您的 spring boot 后端，那么 url 应该是 字符串 url = 'http://10.0.2.2:8080/users/auth/{用户名}/{密码}';

2. 如果您正在使用真实的 Android 手机测试您的后端，请定义入站防火墙规则(在 windows defender 防火墙中)并在防火墙规则中允许端口 80。 获取您系统的IP地址，并将url更改为 String url = 'http://ip:8080/users/auth/{用户名}/{密码}';

https://stackoverflow.com/questions/56431624/