Form表单

//导入Material UI 组件库
import 'package:flutter/material.dart';

//程序入口
void main() {
  runApp(const MaterialApp(home: MyForm()));
}

//表单
class MyForm extends StatefulWidget {
  const MyForm({Key? key}) : super(key: key);

  @override
  State<StatefulWidget> createState() => _FormState();
}

class _FormState extends State<MyForm> {
  //使用Map收集数据，而非TextEditingController
  final Map<String, dynamic> _inputMap = {};

  //FormState为Form的状态类
  final GlobalKey _formKey = GlobalKey<FormState>();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text("MyForm"),
      ),
      body: Form(
        key: _formKey,
        autovalidateMode: AutovalidateMode.onUserInteraction,
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.center,
          children: [
            TextFormField(
              maxLines: 1,
              maxLength: 64,
              //自动获取焦点
              autofocus: true,
              //自动校验模式
              autovalidateMode: AutovalidateMode.disabled,
              decoration: const InputDecoration(
                  labelText: "账号",
                  hintText: "手机或邮箱",
                  prefixIcon: Icon(Icons.person)),
              onChanged: (val) {
                _inputMap['acct'] = val;
              },
              validator: (val) {
                print('acct validator');
                return val!.trim().isNotEmpty ? null : "账号不能为空";
              },
            ),
            TextFormField(
              maxLines: 1,
              maxLength: 12,
              //隐藏文本
              obscureText: true,
              decoration: const InputDecoration(
                  labelText: "密码",
                  hintText: "登录密码",
                  prefixIcon: Icon(Icons.lock)),
              onChanged: (val) {
                _inputMap['pass'] = val;
              },
              validator: (val) {
                print('pass validator');
                return val!.trim().length > 5 ? null : "密码不能少于6位";
              },
            ),
            TextButton(
              child: const Text('登录'),
              onPressed: () {
                //调用validate触发所有FormField的validate回调
                if ((_formKey.currentState as FormState).validate()) {
                  print("验证通过: $_inputMap");
                }
              },
            )
          ],
        ),
      ),
    );
  }
}