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Flutter中的Form表单

　由 孙亚洲 发布于 2023-03-18 2023-03-18T06:50:00+00:00
最后更新: 04-02 2024-04-02T11:42:11+00:00

前言

本文具有强烈的个人感情色彩,如有观看不适,请尽快关闭. 本文仅作为个人学习记录使用,也欢迎在许可协议范围内转载或分享,请尊重版权并且保留原文链接,谢谢您的理解合作. 如果您觉得本站对您能有帮助,您可以使用RSS方式订阅本站,感谢支持!.

笔记

在学习flutter中处理用户名和密码输入的问题时,Flutter这边轻松搞定,学完后发现flutter内置的能力非常强大.下面是记录用户名密码输入的简单demo.

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import 'package:flutter/material.dart';

///创建
void main () {
  runApp(MyApp());
}

class MyApp extends StatelessWidget  {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: "hello flutter",
      home: Scaffold(
        appBar: AppBar(
          title: Text("sunyazhou.com"),
        ),
        body: ContentWidget(),
      ),
    );
  }
}

class LoginWidgetState extends State<LoginWidget> {
  String username = "";
  String password = "";
  GlobalKey<FormState> formGlobalKey = GlobalKey();
  @override
  Widget build(BuildContext context) {
    return Form(
        key: formGlobalKey,
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            TextFormField(
              decoration: InputDecoration(
                  icon: Icon(Icons.people),
                  labelText: "用户名",

              ),
              onSaved: (value) {
                  print("执行了username的 onSaved:$value");
                  this.username = value!;
              },
              validator: (value) {
                if (value == null || value.length == 0) {
                  return "用户名不能为空!";
                }
                return null;
              },
            ),
            TextFormField(
              obscureText: true,
              decoration: InputDecoration(
                icon: Icon(Icons.lock),
                labelText: "密码",
              ),
              onSaved: (value) {
                print("执行了password的 onSaved:$value");
                this.password = value!;
              },
              validator: (value) {
                if (value == null || value.length == 0) {
                  return "密码不能为空!";
                }
                return null;
              },
            ),
            SizedBox(height: 20,),
            Container(
              width: double.infinity,
              height: 44,
              child: ElevatedButton(
                child: Text("登录", style: TextStyle(fontSize: 20, color: Colors.white),),
                onPressed: () {
                  print("注册按钮被点击");
                  formGlobalKey.currentState?.validate();
                  formGlobalKey.currentState?.save();
                  print("username:$username, password:$password");
                },
              ),
            ),
          ],
        ),
    );
  }
}

上面的代码不但具备输入框的功能,还具备输入框内的内容校验,当发生错误的时候 可以使用formGlobalKey拿到当前State调用validate()函数来触发输入框的校验方法.

1

formGlobalKey.currentState?.validate();

这步的操作原理大概是

  1. 声明GlobalKey
  2. 把声明的GlobalKey 的实例传入到 Form中
  3. 通过调用formGlobalKey.currentState?.validate();函数来调用其表单内子控件的方法validator来校验
  4. 最后提交服务端登操作校验提交内容

总结

不得不说flutter还是有他的优势的,通过表单控件完成对children的方法注入.从而实现协议约束的形式, 代码简洁高效.

下面附上学习其他控件的记录

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class ContentWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: const EdgeInsets.all(20.0),
      child: LoginWidget(),
    );
  }
}

class LoginWidget extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return LoginWidgetState();
  }
}

class RegisterWidget extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return RegisterWidgetState();
  }
}

class RegisterWidgetState extends State <RegisterWidget> {
  final textEditingController = TextEditingController();

  @override
  void initState() {
    // TODO: implement initState
    textEditingController.text = "默认值";
    textEditingController.addListener(() {
        print("监听到值的变化: ${textEditingController.text}");
    });
  }
  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: const EdgeInsets.all(20.0),
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          TextField(
              decoration: InputDecoration(
                icon: Icon(Icons.people),
                labelText: "username",
                hintText: "请输入用户名",
                border: OutlineInputBorder(
                  borderSide: BorderSide(width: 1),
                ),
                // filled: true,
                // fillColor: Colors.purple,
              ),
            onChanged: (value) {
                print("当前值 $value");
            },
            onSubmitted: (value) {
                print("最后提交值:$value");
            },
            controller: textEditingController,
          ),
        ],
      ),
    );
  }
}

class RadiusImageDemo extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Center(
      child: ClipRRect(
        borderRadius: BorderRadius.circular(16),
        child: Image.network("https://www.sunyazhou.com/assets/images/avatar.jpg",
          width: 150,
          height: 150,
        ),
      ),
    );
  }
}

class CircleImageDemo extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return ClipOval(
      child: Image.network("https://www.sunyazhou.com/assets/images/avatar.jpg",
        width: 150,
        height: 150,
      ),
    );
  }
}

class AssertImageDemo extends StatelessWidget
{
  @override
  Widget build(BuildContext context) {
    return Image.asset("assets/images/3.webp");
  }
}

class NetworkImageDemo extends StatelessWidget
{
  @override
  Widget build(BuildContext context) {
    return Center(
      child: Container(
        width: 300,
        height: 300,
        color: Colors.red,
        child: Image.network("https://www.sunyazhou.com/assets/images/20230312FlutterLifeCycle/flutter3.webp",
          // fit: BoxFit.cover,
          repeat: ImageRepeat.repeatY,
        ),

      ),
    );
  }
}

class ButtonDemo extends StatelessWidget
{
  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        ElevatedButton(
          child: Text("ElevatedButton"),
          onPressed: () => print("ElevatedButton click"),
        ),
        OutlinedButton(
          child: Text("OutlinedButton"),
          onPressed: () => print("OutlinedButton click"),
        ),
        FloatingActionButton(
          child: Text("FloatingActionButton"),
          onPressed: () => print("FloatingActionButton click"),
        ),

      ],
    );
  }
}

class TextRichDemo extends StatelessWidget
{
  @override
  Widget build(BuildContext context) {
    return Text.rich(
      TextSpan(
        children: [
          TextSpan(
              text: "sunyazhou.com", style: TextStyle(fontSize: 30, fontWeight: FontWeight.bold, color: Colors.red)
          ),
          TextSpan(
              text: "sunyazhou", style: TextStyle(fontSize: 18,color: Colors.blue)
          ),
          TextSpan(text: "\n本文具有强烈的个人感情色彩,如有观看不适,请尽快关闭. \n本文仅作为个人学习记录使用,也欢迎在许可协议范围内转载或使用,\n请尊重版权并且保留原文链接,谢谢您的理解合作. 如果您觉得本站对您能有帮助,您可以使用RSS方式订阅本站,这样您将能在第一时间获取本站信息.",style: TextStyle(fontSize: 20, color:  Colors.deepOrangeAccent)),

        ],
      ),
      textAlign: TextAlign.center,
    );
  }
}

class TextDemo extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Text("本文具有强烈的个人感情色彩,\n如有观看不适,请尽快关闭. \n本文仅作为个人学习记录使用,也欢迎在许可协议范围内转载或使用,"
      ,style: TextStyle(
        fontSize: 20,
        color: Colors.lightBlue,
      ),
      textAlign: TextAlign.center,
      // maxLines: 2,
      overflow: TextOverflow.ellipsis,
      // textScaleFactor: 2,
    );
  }
}
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