问为http POST请求从flutter上的TextFormField捕获数据

EN

class LoginScreen extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => _LoginScreenState();
}

class _LoginScreenState extends State<LoginScreen> {

  final _usernameController = TextEditingController();
  final _passwordController = TextEditingController();

  @override
  Widget build(BuildContext context) {
    return Column(
      children: <Widget>[
        TextFormField(controller: _usernameController,),
        TextFormField(controller: _passwordController, obscureText: true,),
        RaisedButton(
          onPressed: _performLogin,
          child: Text('Login'),
        )
      ],
    );
  }

  void _performLogin() {
    String username = _usernameController.text;
    String password = _passwordController.text;

    print('login attempt: $username with $password');
  }
}

import 'package:flutter/material.dart';
import '../mixins/validate_mixin.dart';

class LoginScreen extends StatefulWidget{
  final GlobalKey<ScaffoldState> scaffoldKey;
  LoginScreen(this.scaffoldKey);
  @override
  State<StatefulWidget> createState() {
    return LoginScreenState(scaffoldKey);
  }
}

class LoginScreenState extends State<LoginScreen>  with ValidateMixin{
  final formKey = GlobalKey<FormState>();
  final GlobalKey<ScaffoldState> scaffoldKey;

  LoginScreenState(this.scaffoldKey);

  String _email;
  String _password;

  @override
  Widget build(BuildContext context) {
    return Container(
      margin: EdgeInsets.all(40.0),
      child: Form(
        key: formKey,
        child: Column(
          children: <Widget>[
            emailField(),
            passwordField(),
            Container(margin: EdgeInsets.only(bottom: 25.0),),
            submitButton(),
          ],
        ),
      ),
    );
  }

  Widget emailField() {
    return TextFormField(
      decoration: InputDecoration(hintText: 'ali@gmail.co', labelText: 'Email'),
      keyboardType: TextInputType.emailAddress,
      validator: validateEmail,
      onSaved: (String value) {
        _email = value;
      },
    );
  }

  Widget passwordField() {
    return TextFormField(
      obscureText: true,
      decoration: InputDecoration(hintText: '*****', labelText: 'Password'),
      onSaved: (String value) {
        _password = value;
      },
    );
  }

  Widget submitButton() {
    return RaisedButton.icon(
      color: Colors.cyan[900],
      textColor: Colors.white,
      label: Text('Submit'),
      icon: Icon(Icons.save), 
      onPressed: () {
        final bool v = formKey.currentState.validate();
        if (v) {
          formKey.currentState.save();
          _performLogin();
          print('object');
        }
    },);
  }

  void _performLogin () {
    var snackbar = new SnackBar(
      content: Text('Email: $_email and Password $_password'),
    );
    scaffoldKey.currentState.showSnackBar(snackbar);
  }
}