TextFormField 文字表单输入

和TextField属性基本一致，在其基础上增加字段的校验和提交的回调，FormState的save会触发onSaved回调。

相关组件

TextField Form

TextFormField基本使用

基本属性和TextField一致，详见之
【validator】 : 验证函数 【FormFieldValidator 】
【onFieldSubmitted】 : 提交回调 【ValueChanged】
【onSaved】 : 表单save时回调 【FormFieldSetter】

import 'package:flutter/material.dart';
class CustomTextFormField extends StatefulWidget {
  @override
  _CustomTextFormFieldState createState() => _CustomTextFormFieldState();
}
class _CustomTextFormFieldState extends State<CustomTextFormField> {
  GlobalKey<FormState> _formKey = GlobalKey<FormState>();
  @override
  Widget build(BuildContext context) {
    return Container(
      child: Form(
        key: _formKey,
        child:
        Stack(
          alignment: Alignment.centerRight,
          children: <Widget>[
            Container(
              width: 350,
              child: UnconstrainedBox(
                child: Container(
                  width: 200,
                  height: 70,
                  child: TextFormField(
                    style: TextStyle(textBaseline: TextBaseline.alphabetic),
                    decoration: InputDecoration(
                      border: OutlineInputBorder(),
                      labelText: 'username',
                    ),
                    validator: _validateUsername,
                    onFieldSubmitted: _onFieldSubmitted,
                    onSaved: _onSaved,
                  ),
                ),
              ),
            ),
            Positioned(
                top: 0, right: 0, child: _buildSubmitButton(context)),
          ],
        ),
      ),
    );
  }
  String _validateUsername(value) {
    if (value.isEmpty) {
      return '用户名不能为空';
    }
    return null;
  }
  _onSaved(value){
    print('onSaved:'+value);
  }
  void _onFieldSubmitted(value) {
    print('onFieldSubmitted:'+value);
  }
  RaisedButton _buildSubmitButton(BuildContext context) {
    return RaisedButton(
      color: Colors.blue,
      shape: CircleBorder(
        side: BorderSide(width: 2.0, color: Color(0xFFFFDFDFDF)),
      ),
      onPressed: _onSubmit,
      child: Icon(
        Icons.check,
        color: Colors.white,
      ),
    );
  }
  _onSubmit(){
    _formKey.currentState.save();
    if (_formKey.currentState.validate()) {
      FocusScope.of(context).requestFocus(FocusNode());
    }
  }
}