Develop Reference

Is it possible to update TextFormField using shared state (and without violating good practices)?

I am trying to make test project according to good practices.
Please note that I DON'T want any "hacky" approach. I am willing to learn good way of solving it.
My understanding of "lifting state up" is that any change updates the state, and then view is redrawn (rebuild) using current state. It is great in theory, but it DOES NOT work with TextFormField/TextEditingController.
I want to have a SharedState and bi-directonal TextFormField/TextEditingController, as follows:
case 1 (works):
TextFormField changes -> state is updated -> readonly Text (in WidgetTwo) is updated
case 2 (does not work):
button (in WidgetOne) is clicked -> state is updated -> TextFormField (in WidgetThree) shows new value from state
I have code in 3 different widgets + main file + SharedSate:
main.dart
void main() {
runApp(ChangeNotifierProvider(
create: (_) => sharedState(), child: const MyApp()));
}
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
// This widget is the root of your application.
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: const MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatelessWidget {
final String title;
const MyHomePage({Key? key, required this.title}) : super(key: key);
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
WidgetOne(),
WidgetTwo(),
WidgetThree(),
]),
),
);
}
}
shared_state.dart
class SharedState extends ChangeNotifier {
int counter = 0;
void setCounter(int c) {
counter = c;
notifyListeners();
}
void incrementCounter() {
counter++;
notifyListeners();
}
void decrementCounter() {
counter--;
notifyListeners();
}
Future fetchCounterFromWeb() async {
// simulate external call
await Future.delayed(Duration(milliseconds: 500));
setCounter(42);
}
}
widget_one.dart
class WidgetOne extends StatelessWidget {
#override
Widget build(BuildContext context) {
var state = Provider.of<SharedState>(context, listen: false);
return Row(
children: [
ElevatedButton(
onPressed: () => state.decrementCounter(),
child: Text('decrement')),
ElevatedButton(
onPressed: () => state.incrementCounter(),
child: Text('increment')),
ElevatedButton(
onPressed: () => state.fetchCounterFromWeb(),
child: Text('fetch counter from web')),
],
);
}
}
widget_two.dart
class WidgetTwo extends StatelessWidget {
#override
Widget build(BuildContext context) {
var state = Provider.of<SharedState>(context, listen: true);
return Row(
children: [Text('Value of counter is: ${state.counter}')],
);
}
}
widget_three.dart (problem is here)
class WidgetThree extends StatefulWidget {
#override
State<StatefulWidget> createState() {
return WidgetThreeState();
}
}
class WidgetThreeState extends State<WidgetThree> {
final GlobalKey<FormState> _formKey = GlobalKey<FormState>();
late TextEditingController _controller;
#override
void initState() {
super.initState();
var state = Provider.of<SharedState>(context, listen: false);
_controller = TextEditingController(text: state.counter.toString());
}
#override
Widget build(BuildContext context) {
var state = Provider.of<SharedState>(context, listen: true);
// THE ISSUE:
// It is NOT possible to update Controller (or TextEditing field)
// without this hacky line (which is not good practice)
_controller.text = state.counter.toString();
return Form(
key: _formKey,
child: Column(children: [
TextFormField(
controller: _controller,
keyboardType: TextInputType.number,
onChanged: (v) {
state.setCounter(int.parse(v.isEmpty ? '0' : v));
},
)
]),
);
}
}
I know I can possible move TextEditingController to SharedState, but SharedState should be UI agnostic, and TextEditingController is a UI widget.

Methods are not getting executed in the written order inside onPressed

Im trying to create a flutter app with a simple raised button that does the following:
sends an sms in the background using the sms package opens a webpage
2. in the app(only for 5 seconds) using url_launcher opens the phones
3. native app for making a voice call with the onPressed property.
And I wanted it to be in this order so that I can make the phone call at the end. However, the inside the onPressed opens the native phone call app first, which doesnt let my web page open unless I exit out of the phone call app.
Im having a hard time understanding why the phone call native app is opened first, even though I make the call the _makePhoneCall() method only after I make the _launchInApp(toLaunch) call. sendSMS() is being called correctly
How can I set this in a way that the phone call native app is called only after the webpage is opened in the app and follows the order? Any help would be great
Below is the piece of code:
import 'package:flutter/material.dart';
import 'package:url_launcher/url_launcher.dart';
import 'package:sms/sms.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Packages testing',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(title: 'Packages testing'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
String _phone = '';
_launchInApp(String url) async {
if (await canLaunch(url)) {
await launch(
url,
forceSafariVC: true,
forceWebView: true,
headers: <String, String>{'my_header_key': 'my_header_value'},
);
} else {
throw 'Could not launch $url';
}
}
_makePhoneCall(String url) async {
if (await canLaunch(url)) {
await launch(url);
} else {
throw 'Could not launch $url';
}
}
void sendSMS() {
SmsSender sender = new SmsSender();
sender.sendSms(new SmsMessage(_phone, 'Testing Handset'));
}
#override
Widget build(BuildContext context) {
const String toLaunch = 'https://flutter.dev/';
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: ListView(
children: <Widget>[
Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Padding(
padding: const EdgeInsets.all(16.0),
child: TextField(
onChanged: (String text) => _phone = text,
decoration:
const InputDecoration(hintText: 'Phone Number')),
),
FlatButton(
onPressed: () => setState(() {
sendSMS();
_launchInApp(toLaunch);
_makePhoneCall('tel:$_phone');
}),
child: const Text('Run All'),
),
const Padding(padding: EdgeInsets.all(16.0)),
],
),
],
),
);
}
}

You will have to use the await keyword before the _launchInApp function to make it work properly. Try the following code.
FlatButton(
onPressed: () aync {
sendSMS();
await _launchInApp(toLaunch);
_makePhoneCall('tel:$_phone');
}),
child: const Text('Run All'),
),

You created async functions but when you called them you did not specify that you want to wait for them to complete. Add the await keyword in OnPressed

connect Flutter code from different sources like for example youtube tutorials

Hello Guys im new to flutter.
To understand Flutter I watched a lot of videos and read blog entries.
But there is always a problem:
Each video is about a specific topic and all of them start with a new Flutter project. As long as I want to continue working on the code I can't change the code.
Below I have added a code by Hanz Müller as an example. Topic NavigationBar.
But now I want to delete the text under the icons and edit the different app pages (body) with text and images.
I can't delete the text under the icons because text can't be ''null''.
And I can't edit the diffrent body pages because I can't find the position.
i only know html and css because it is a hobby and now i search for the place where i find the body container :)
Thanks a lot for your help
import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';
class Destination {
const Destination(this.title, this.icon, this.color);
final String title;
final IconData icon;
final MaterialColor color;
}
const List<Destination> allDestinations = <Destination>[
Destination('Home', Icons.home, Colors.teal),
Destination('Business', Icons.business, Colors.cyan),
Destination('School', Icons.school, Colors.orange),
Destination('Flight', Icons.flight, Colors.blue)
];
class DestinationView extends StatefulWidget {
const DestinationView({ Key key, this.destination }) : super(key: key);
final Destination destination;
#override
_DestinationViewState createState() => _DestinationViewState();
}
class _DestinationViewState extends State<DestinationView> {
TextEditingController _textController;
#override
void initState() {
super.initState();
_textController = TextEditingController(
text: 'sample text: ${widget.destination.title}',
);
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('${widget.destination.title} Text'),
backgroundColor: widget.destination.color,
),
backgroundColor: widget.destination.color[100],
body: Container(
padding: const EdgeInsets.all(32.0),
alignment: Alignment.center,
child: TextField(controller: _textController),
),
);
}
#override
void dispose() {
_textController.dispose();
super.dispose();
}
}
class HomePage extends StatefulWidget {
#override
_HomePageState createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> with TickerProviderStateMixin<HomePage> {
int _currentIndex = 0;
#override
Widget build(BuildContext context) {
return Scaffold(
body: SafeArea(
top: false,
child: IndexedStack(
index: _currentIndex,
children: allDestinations.map<Widget>((Destination destination) {
return DestinationView(destination: destination);
}).toList(),
),
),
bottomNavigationBar: BottomNavigationBar(
currentIndex: _currentIndex,
onTap: (int index) {
setState(() {
_currentIndex = index;
});
},
items: allDestinations.map((Destination destination) {
return BottomNavigationBarItem(
icon: Icon(destination.icon),
backgroundColor: destination.color,
title: Text(destination.title)
);
}).toList(),
),
);
}
}
void main() {
runApp(MaterialApp(home: HomePage(), debugShowCheckedModeBanner: false));
}

If you want to remove the Text under the icon Check the code where the Text widget is place.
So you have the relevant Text widget in BottomNavigationBarItem
title: Text(destination.title)
So if you don't need the Text widget you can simply replace it with Container to display nothing.
title: Text(destination.title)
I would suggest you read the code and understand it will. The better you understand how your widgets are built and rendered it will be easier to modify them.

How to create triple click button in flutter

How can I implement a triple-click button in flutter?
On triple-click, the button will store an entry in Firebase database.

Its pretty easy. You can use a GestureDetector() to check for the number of taps then you can provide your logic if there are 3 taps.
GestureDetector(
onTap: () {
int now = DateTime.now().millisecondsSinceEpoch;
if (now - lastTap < 1000) {
print("Consecutive tap");
consecutiveTaps ++;
print("taps = " + consecutiveTaps.toString());
if (consecutiveTaps == 3){
// Do something
}
} else {
consecutiveTaps = 0;
}
lastTap = now;
},
child: ...
)

Implementing "triple click" button in flutter might not be possible. But, if you really want to make it work ASAP then a simple method could be to maintain a counter for the number of clicks done. Once the count reaches 3, you need to add your entry to Firestore.
I have modified the code from the counter app boilerplate of flutter.
Hope you have cloud_firestore in your pubspec.yaml file. If not then add it and put the services.json as well in the app folder of android or respective directory of ios.
cloud_firestore: ^0.13.4+1
So, now you can have a look at the code that I am using.
import 'package:flutter/material.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
debugShowCheckedModeBanner: false,
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
int _counter = 0;
_incrementCounter() {
setState(() {
_counter++;
});
if (_counter == 3) {
Firestore.instance
.collection('/sampleData')
.add({'data': "data"}).catchError((e) {
print(e);
});
setState(() {
_counter = 0;
});
}
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text(
'You have pushed the button this many times:',
),
Text(
'$_counter',
style: Theme.of(context).textTheme.display1,
),
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: Icon(Icons.add),
),
);
}
}
I have edited the _incrementCounter function. I added a conditional statement to check the _counter if it is 3 or not. Then, I am adding the Firestore entry. Later on, the most important bit is to set the _counter as 0 so that the next time the user presses the button 3 times, then the code will work accordingly. You can customize it according to your needs.
But remember, triple clicks have not been yet invented in flutter and this is just a work-around solution and don't use it for Real-life Development applications as this would be a very bad practice.

How to use barcode_scan widget as a child to some other widget?

I am using barcode_scan widget in my flutter app when I call Scan method this widget takes up the whole screen where it show the camera, I want to show that camera view inside another widget.

You can use package https://pub.dev/packages/last_qr_scanner or https://pub.dev/packages/qr_code_scanner
They both use platform view within Flutter
full example code of last_qr_scanner
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:last_qr_scanner/last_qr_scanner.dart';
void main() => runApp(MyApp());
class MyApp extends StatefulWidget {
const MyApp({
Key key,
}) : super(key: key);
#override
_MyAppState createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
final GlobalKey qrKey = GlobalKey(debugLabel: 'QR');
var qrText = "";
var controller;
#override
void initState() {
super.initState();
}
void _onQRViewCreated(QRViewController controller) {
this.controller = controller;
final channel = controller.channel;
controller.init(qrKey);
channel.setMethodCallHandler((MethodCall call) async {
switch (call.method) {
case "onRecognizeQR":
dynamic arguments = call.arguments;
setState(() {
qrText = arguments.toString();
});
}
});
}
#override
Widget build(BuildContext context) {
return new MaterialApp(
home: new Scaffold(
appBar: new AppBar(
title: new Text('Barcode Scanner Example'),
),
body: Column(
children: <Widget>[
Expanded(
child: LastQrScannerPreview(
key: qrKey,
onQRViewCreated: _onQRViewCreated,
),
flex: 4,
),
Expanded(
child: Text("This is the result of scan: $qrText"),
flex: 1,
),
Expanded(
child: RaisedButton(
onPressed: () {
this.controller.toggleTorch();
},
child: Text("Toggle Torch"),
),
flex: 1,
)
],
),
),
);
}
}

Your camera view must be a flutter widget to be embedded in another widget.
You can use this package which outputs the camera preview on a flutter texture and use the Mobile Vision API to detect QR codes and barcodes : https://github.com/rmtmckenzie/flutter_qr_mobile_vision