Flutter表单验证失效：为何空输入仍能通过验证？

你的代码存在Form组件嵌套的问题：外层Form已经绑定了_formKey，但你在Padding里又嵌套了一个无key的Form，两个TextFormField实际属于内层Form，导致调用_formKey.currentState!.validate()时，根本不会验证这两个输入框，所以空内容也能通过验证跳转。

修复方案 #

删除内层的Form组件，让TextFormField直接归属于绑定_formKey的外层Form，这样验证逻辑就能正常生效。

修改后的完整代码 #

import 'package:fir_project/utils/routes.dart';
import 'package:flutter/material.dart';

class LoginPage extends StatefulWidget {
  const LoginPage({super.key});

  @override
  State<LoginPage> createState() => _LoginPageState();
}

class _LoginPageState extends State<LoginPage> {
  String name = "";
  bool changeButton = false;
  final _formKey = GlobalKey<FormState>();

  moveToHome(BuildContext context) async {
    if (_formKey.currentState!.validate()) {
      setState(() {
        changeButton = true;
      });
      await Future.delayed(const Duration(seconds: 1));
      await Navigator.pushNamed(context, Myroutes.homeRoute);
      setState(() {
        changeButton = false;
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return Material(
        color: Colors.white,
        child: SingleChildScrollView(
          child: Form(
            key: _formKey,
            child: Column(
              children: [
                Image.asset(
                  "assets/images/loginimg.png",
                  fit: BoxFit.cover,
                ),
                const SizedBox(
                  height: 20.0,
                ),
                Text(
                  "Welcome $name",
                  style: const TextStyle(
                    fontSize: 28,
                    fontWeight: FontWeight.bold,
                  ),
                ),
                const SizedBox(
                  height: 20.0,
                ),
                Padding(
                  padding: const EdgeInsets.symmetric(
                      vertical: 16.0, horizontal: 32.0),
                  // 移除内层Form
                  child: Column(
                    children: [
                      TextFormField(
                        decoration: const InputDecoration(
                            hintText: "Enter Username",
                            labelText: "Username"),
                        validator: (value) {
                          if (value == null || value.isEmpty) {
                            return "Username Cannot be Empty";
                          }
                          return null;
                        },
                        onChanged: (value) {
                          name = value;
                          setState(() {});
                        },
                      ),
                      TextFormField(
                        obscureText: true,
                        decoration: const InputDecoration(
                            hintText: "Enter Password",
                            labelText: "Password"),
                        validator: (value) {
                          if (value == null || value.isEmpty) {
                            return "Password Cannot be Empty";
                          }
                          return null;
                        },
                      ),
                      const SizedBox(
                        height: 40.0,
                      ),
                      Material(
                        color: Colors.teal,
                        borderRadius:
                            BorderRadius.circular(changeButton ? 40 : 8),
                        child: InkWell(
                          onTap: () {
                            moveToHome(context);
                          },
                          child: AnimatedContainer(
                            duration: const Duration(seconds: 1),
                            height: 50,
                            width: changeButton ? 50 : 150,
                            alignment: Alignment.center,
                            child: changeButton
                                ? const Icon(
                                    Icons.done,
                                    color: Colors.white,
                                  )
                                : const Text(
                                    "Login",
                                    style: TextStyle(
                                      color: Colors.white,
                                      fontWeight: FontWeight.bold,
                                      fontSize: 20,
                                    ),
                                  ),
                          ),
                        ),
                      )
                    ],
                  ),
                )
              ],
            ),
          ),
        ));
  }
}

内容的提问来源于stack exchange，提问作者Tahmeed Zamindar