TextField

import ‘package:flutter/material.dart‘;


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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: HomePage(),
    );
  }
}

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  TextEditingController _userNameController=TextEditingController();
  TextEditingController _passWordController=TextEditingController();
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Column(
        children: <Widget>[
          TextField(
            controller: _userNameController,
            decoration: InputDecoration(
              icon: Icon(Icons.desktop_windows),
              labelText: ‘输入你的号码‘,
              hintText: ‘输入你的手机号码‘,
            ),
          ),
          TextField(
            controller: _passWordController,
            decoration: InputDecoration(
              icon: Icon(Icons.perm_camera_mic),
              labelText: ‘输入你的密码‘,
              hintText: ‘你的密码安全么‘,
            ),
          ),
          RaisedButton(
            onPressed:(){
              logOn();
            },
            child: Text(‘操你大爷的‘),
          ),
        ],
      ),
    );
  }
  void onTextClear() {
    setState(() {
      _userNameController.clear();
      _passWordController.clear();
    });
  }
  logOn(){
    if(_userNameController.text.length!=11){
      showDialog(
        context: context,
        builder: (context)=>AlertDialog(
          title: Text(‘请输入正确的电话号码‘),
        ),
      );
    }else if(_passWordController.text.length!=6){
      showDialog(
        context: context,
        builder: (context)=>AlertDialog(
          title: Text(‘请输入正确的密码‘),
        ),
      );
    }else{
      showDialog(
        context: context,
        builder: (context)=>AlertDialog(
          title: Text(‘登陆成功‘),
        ),
      );
      onTextClear();
    }
  }
}

TextField

原文：https://www.cnblogs.com/braveheart007/p/10806349.html