Flutter中form表单使用

使用了Form、TextFormField

class _MyHomePageState extends State<MyHomePage> {
  final GlobalKey<FormState> _formKey = new GlobalKey<FormState>();
  String _name;
  String _password;

  // 提交
  void _onSubmit() {
    final form = _formKey.currentState;
    if (form.validate()) {
      form.save();
      _showMessage('用户名是：$_name，密码是：$_password');
    }
  }

  // 展示提示框
  void _showMessage(String val) {
    showDialog<Null>(
      context: context,
      builder: (BuildContext context) {
        return new AlertDialog(
          title: Text('提示'),
          content: Text('$val'),
          actions: <Widget>[
            FlatButton(
              onPressed: () {
                _formKey.currentState.reset();
                Navigator.pop(context);
              },
              child: Text('确定'),
            ),
          ],
        );
      },
    );
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: AppBar(
        title: Text('我是title'),
      ),
      body: ListView(
        children: <Widget>[
          Form(
            key: _formKey,
            onChanged: () {
              print('onChanged');
            },
            child: new Column(
              children: <Widget>[
                new TextFormField(
                  decoration: new InputDecoration(
                    labelText: '用户名',
                  ),
                  onSaved: (val) => this._name = val,
                  validator: (val) {
                    if (val == null || val.isEmpty) {
                      return '请输入用户名';
                    }
                    if (val.length > 18 || val.length < 6) {
                      return '用户名长度在6-18字符之间';
                    }
                    return null;
                  }
                ),
                new TextFormField(
                  decoration: new InputDecoration(
                    labelText: '密码',
                  ),
                  onSaved: (val) => this._password = val,
                  validator: (val) {
                    if (val == null || val.isEmpty) {
                      return '请输入密码';
                    }
                    if (val.length != 6) {
                      return '密码应为6位字符';
                    }
                    return null;
                  }
                ),
                new Row(
                  children: <Widget>[
                    MaterialButton(
                      onPressed: () {
                        _formKey.currentState.reset();
                        _showMessage('用户名密码已经重置');
                      },
                      child: Text('重置'),
                    ),
                    MaterialButton(
                      onPressed: _onSubmit,
                      child: Text('提交'),
                    ),
                  ],
                ),
              ],
            ),
          )
        ],
      ),
    );
  }
}

结果：

Simulator Screen Shot - iPhone XS - 2019-01-23 at 10.34.23.png
Simulator Screen Shot - iPhone XS - 2019-01-23 at 10.34.49.png