如何从textfromfield保存值并将其传递回页面?

Question

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),
),
),
),
),

],
),
),
]),
);
}
}

和我得到下面显示的错误:

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

我只是想获得textfromfield值，我想把它传递给home。在firebase collection

中创建文档

Answer 1

你必须定义一个edittextcontrol () ex:textController并将其设置为TextFormField作为控制器参数，然后获取text作为textController。

Answer 2

for从第一屏幕传递到第二屏幕

首先/

TextEditingController controller = TextEditingController();

Secoundly/

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),),
);
},
),
),

Answer 3

您在TextFormField中添加了key

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'),
),
),
),

从TextFormField中删除并添加到Form

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'),
),
),
),

这将解决您的问题