Question

我尝试为用户创建登录页面，但出现错误类型'_InternalLinkedHashMap '不是'String'类型的子类型。我做了很多尝试来找出问题的原因，但我没有找到解决方案。我是一名新的开发人员。我也在这里查看了该站点以前的帖子，但仍然无法解决问题。

import 'package:flutter/material.dart';
import 'dart:convert';
import 'package:http/http.dart' as http;
import 'package:onefrist/main.dart';
import 'package:shared_preferences/shared_preferences.dart';
import 'MyPreferences.dart';
import 'main.dart';
import 'Registration.dart';

void main() => runApp(loginpage());

String getid;
class loginpage extends StatelessWidget {

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        home: Scaffold(
            appBar: AppBar(
                backgroundColor: Colors.amber,
                title: Text('User Login Form')),
            body: Center(
                child: LoginUser()
            )
        )
    );
  }
}

class LoginUser extends StatefulWidget {
  LoginUserState createState() => LoginUserState();

}

class LoginUserState extends State <LoginUser>{
  MyPreferences _myPreferences = MyPreferences();
  var getid;

  @override
  void initState() {
    // TODO: implement initState
    super.initState();

    _myPreferences.init().then((value) {
      setState(() {
        _myPreferences = value;

      });
    });
  }




  bool visible = false ;
  Future userLogin() async{
    setState(() {
      visible = true ;

    });

    final emailController = TextEditingController(text: _myPreferences.user);
    final passwordController = TextEditingController(text: _myPreferences.password);
   
    String email = emailController.text;
    String password = passwordController.text;
 
    if(email == '' || password == '')
    {
  
    }else{

      var url = 'http://xxxxxxxxx/login_user.php';
      var data = {'email': email, 'password' : password};
      var response = await http.post(url, body: json.encode(data));
      var message = jsonDecode(response.body);
      print("tapped ${message['id']}");
      getid=message['id'];
      _myPreferences.id = getid;
      _myPreferences.commit();


      if(message['result'] == 'Login Matched')

      {
        setState(() {
          visible = false;


        });

        Navigator.push(context, MaterialPageRoute(builder: (context) => mainpage(email : emailController.text)));
      }else{
        setState(() {
          visible = false;

        });

        // Showing Alert Dialog with Response JSON Message.
        showDialog(
          context: context,
          builder: (BuildContext context) {
            return AlertDialog(
              title: new Text(message),
              actions: <Widget>[
                FlatButton(
                  child: new Text("OK"),
                  onPressed: () {
                    Navigator.of(context).pop();
                  },
                ),
              ],
            );
          },
        );}
    }
  }


}

════════ Exception caught by widgets library ═══════════════════════════════════════════════════════
The following _TypeError was thrown building Builder(dirty):
type '_InternalLinkedHashMap<String, dynamic>' is not a subtype of type 'String'

The relevant error-causing widget was: 
  MaterialApp file:///C:/Users/MARWAN/IdeaProjects/onefrist/lib/loginpage.dart:18:12
When the exception was thrown, this was the stack: 
#0      LoginUserState.userLogin.<anonymous closure> (package:onefrist/loginpage.dart:112:31)
#1      Builder.build (package:flutter/src/widgets/basic.dart:7118:48)
#2      StatelessElement.build (package:flutter/src/widgets/framework.dart:4620:28)
#3      ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4546:15)
#4      Element.rebuild (package:flutter/src/widgets/framework.dart:4262:5)
...
════════════════════════════════════════════════════════════════════════════════════════════════════

如果有人知道解决方案对我有帮助

Answer 1

Map<String,dynamic> message = jsonDecode(response.body);

请尝试

类型'_InternalLinkedHashMap <String，dynamic>'不是'String'类型flutter的子类型

1 个答案: