如何從textfromfield保存值并將其傳回頁面？

import 'package:flutter/material.dart';
import 'package:mmitra/widgets/header.dart';
import 'home.dart';

class CreateAccount extends StatefulWidget {
  
  @override
  _CreateAccountState createState() => _CreateAccountState();
}

class _CreateAccountState extends State<CreateAccount> {
  late String username;
  final _key = Global Key<FormState>();

  

  @override
  Widget build(BuildContext parentContext) {
    return Scaffold(
      appBar: header(context, titleText: 'Create Account'),
      body: ListView(children: [
        Container(
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.center,
            children: [
              Padding(
                padding: EdgeInsets.only(top: 25),
                child: Center(
                  child: Text(
                    'Create a username',
                    style: TextStyle(fontSize: 25.0),
                  ),
                ),
              ),
              Padding(
                padding: EdgeInsets.all(16.0),
                child: Form(
                  child: TextFormField(
                    key: _key,
                    // controller: myController,
                    onSaved: (val) => username = val!,

                    decoration: InputDecoration(
                        border: OutlineInputBorder(),
                        labelStyle: TextStyle(fontSize: 15),
                        labelText: 'Username',
                        hintText: 'Must be at least 3 Characters'),
                  ),
                ),
              ),
              GestureDetector(
                onTap: () {
                  _key.currentState!.save();
                  Navigator.pop(context, username
                      );
                },
                child: Container(
                  height: 50,
                  width: 300,
                  decoration: BoxDecoration(
                      color: Colors.blue,
                      borderRadius: BorderRadius.circular(7)),
                  child: Center(
                    child: Text(
                      'Submit',
                      style:
                          TextStyle(fontSize: 15, fontWeight: FontWeight.bold),
                    ),
                  ),
                ),
              ),
              
            ],
          ),
        ),
      ]),
    );
  }
}

我得到以下顯示的錯誤：

Exception caught by gesture  
The following Cast Error was thrown while handling a gesture  
Null check operator used on a null value

我只想獲取 textfromfield 值，我想將它傳遞給 home.dart 頁面，以便在 firebase 集合中創建檔案

uj5u.com熱心網友回復：

您在TextFormField 中添加了鍵

 Form(
              child: TextFormField(
                key: _key,
                // controller: myController,
                onSaved: (val) => username = val!,

                decoration: InputDecoration(
                    border: OutlineInputBorder(),
                    labelStyle: TextStyle(fontSize: 15),
                    labelText: 'Username',
                    hintText: 'Must be at least 3 Characters'),
              ),
            ),
          ),

從TextFormField 中洗掉它并在Form 中添加它

就像：

 Form(
           key: _key,
              child: TextFormField(
                
                // controller: myController,
                onSaved: (val) => username = val!,

                decoration: InputDecoration(
                    border: OutlineInputBorder(),
                    labelStyle: TextStyle(fontSize: 15),
                    labelText: 'Username',
                    hintText: 'Must be at least 3 Characters'),
              ),
            ),
          ),

這將解決您的問題。

uj5u.com熱心網友回復：

您必須定義一個 EditTextControll() ex:textController 并將其設定為 TextFormField 到控制器引數，然后將文本作為 textController.text 獲取并通過 Navigator 傳遞。

uj5u.com熱心網友回復：

用于將第一個螢屏傳遞到兩個螢屏

首先 /

TextEditingController controller = TextEditingController();

其次 /

body: Form(
        child: TextFormField(
          controller: controller,
          onTap: (){
            //here SettingsScreen() is example
            // name is paramerter in the secound screen
            Navigator.push(context,
              MaterialPageRoute(builder: (context)=>SettingsScreen(name:controller.text),),
            );
          },
        ),
      ),

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