从Flutter中的弹出式导航器接收响应 [英] Receive Response from pop navigator in Flutter
问题描述
这是导航器为称为的表单推送的简单代码示例.并弹出一个答案.我的目标是弹出一个对象,而不是字符串,但保持其简单性仍然行不通.
Here is a simple example of code that navigator push for a form called. and pop for an answer. my goal is to make a pop of an object, not a string, but keeping it that simple still doesn't work.
main.dart:
main.dart:
import 'package:flutter/material.dart';
import 'answer.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
final appTitle = 'Form Validation Demo';
return MaterialApp(
title: appTitle,
home: Scaffold(
appBar: AppBar(
title: Text(appTitle),
),
body: ShowData(),
),
);
}
}
// Create a Form widget.
class MyCustomForm extends StatefulWidget {
@override
MyCustomFormState createState() {
return MyCustomFormState();
}
}
// Create a corresponding State class.
// This class holds data related to the form.
class MyCustomFormState extends State<MyCustomForm> {
// Create a global key that uniquely identifies the Form widget
// and allows validation of the form.
//
// Note: This is a GlobalKey<FormState>,
// not a GlobalKey<MyCustomFormState>.
final _formKey = GlobalKey<FormState>();
final myController = TextEditingController();
String stateData;
@override
void dispose() {
// Clean up the controller when the widget is disposed.
myController.dispose();
super.dispose();
}
@override
Widget build(BuildContext context) {
// Build a Form widget using the _formKey created above.
return Scaffold(
body: Form(
key: _formKey,
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
TextFormField(
controller: myController,
validator: (value) {
if (value.isEmpty) {
return 'Please enter some text';
}
return null;
},
onSaved: (value){
stateData = value;
},
),
Padding(
padding: const EdgeInsets.symmetric(vertical: 16.0),
child: RaisedButton(
onPressed: () {
// Validate returns true if the form is valid, or false
// otherwise.
if (_formKey.currentState.validate()) {
_formKey.currentState.save();
// If the form is valid, display a Snackbar.
Navigator.pop(context,stateData);
// Scaffold.of(context)
// .showSnackBar(SnackBar(content: Text(myController.text)));
// myController.text = 'look at me';
}
},
child: Text('Submit'),
),
),
],
),
),
);
}
}
answer.dart:
answer.dart:
import 'package:flutter/material.dart';
import 'main.dart';
class ShowData extends StatefulWidget {
@override
_ShowDataState createState() => _ShowDataState();
}
class _ShowDataState extends State<ShowData> {
String data = 'start';
@override
Widget build(BuildContext context) {
return Scaffold(
floatingActionButton: FloatingActionButton(onPressed: (){
String holder = getFormData(context);
setState(() {
data = holder;
});
},
elevation: 4,
),
body:Text(data,style: TextStyle(fontSize: 80),));
}
String getFormData(BuildContext context) {
final Future<String> answer = Navigator.push(context,MaterialPageRoute(builder: (context)=>MyCustomForm()));
answer.then((String value) {
return value != null? value: 'empty';
}
);
}
}
从表单错误消息返回时:
when returning from the form error message is :
'package:flutter/src/widgets/text.dart':断言失败:行...pos ...'data!= null':必须为文本提供非null的字符串小部件.
'package:flutter/src/widgets/text.dart': Failed assertion: line ... pos... 'data!=null': A non-null String must be provided to a Text widget.
推荐答案
添加等待以接收来自Future的结果并返回值;
Add await to receive the result from Future and return the value;
Future<String> getFormData(BuildContext context) async {
final result = await Navigator.push(
context, MaterialPageRoute(builder: (context) => MyCustomForm()));
return Future.value(result);
}
修改 FloatingActionButton
onPressed代码以接收将来的字符串
Modify the FloatingActionButton
onPressed code to receive Future String
onPressed: () async {
final value = await getFormData(context);
setState(() {
data = value;
});
},
这篇关于从Flutter中的弹出式导航器接收响应的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!