my flutter app is crashing after I press the back arrow on the phone.
how to make the error happen:
1 -
this button sends to a route that uses google maps.
ElevatedButton(
child: Text('Profesional'),
onPressed: () {
Navigator.push(
context,
MaterialPageRoute(builder: (context) => MyApp2()),
);
},
),
2-
This shows a live map that tracks the position of your phone.
import 'package:google_maps_flutter/google_maps_flutter.dart';
import 'package:flutter/material.dart';
import 'package:location/location.dart';
class MyApp2 extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner: false,
home: MyHomePage(),
);
}
}
class MyHomePage extends StatefulWidget {
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
LatLng _initialcameraposition = LatLng(20.5937, 78.9629);
GoogleMapController _controller;
Location _location = Location();
void _onMapCreated(GoogleMapController _cntlr) {
_controller = _cntlr;
_location.onLocationChanged.listen((l) {
_controller.animateCamera(
CameraUpdate.newCameraPosition(
CameraPosition(target: LatLng(l.latitude, l.longitude), zoom: 15),
),
);
});
}
#override
Widget build(BuildContext context) {
return Scaffold(
body: Container(
height: MediaQuery.of(context).size.height,
width: MediaQuery.of(context).size.width,
child: Stack(
children: [
GoogleMap(
initialCameraPosition:
CameraPosition(target: _initialcameraposition),
mapType: MapType.normal,
onMapCreated: _onMapCreated,
myLocationEnabled: true,
),
],
),
),
);
}
}
3 -
When I press the back button of the phone, the app crashes and shows me this. which is inside a platform_channel.dart file that I believe is created automatically.
BinaryMessenger get binaryMessenger => _binaryMessenger ?? ServicesBinding.instance!.defaultBinaryMessenger;
final BinaryMessenger? _binaryMessenger;
#optionalTypeArgs
Future<T?> _invokeMethod<T>(String method, { required bool missingOk, dynamic arguments }) async {
assert(method != null);
final ByteData? result = await binaryMessenger.send(
name,
codec.encodeMethodCall(MethodCall(method, arguments)),
);
if (result == null) {
if (missingOk) {
return null;
}
*throw MissingPluginException('No implementation found for method $method on channel $name');*
}
return codec.decodeEnvelope(result) as T?;
}
the program (Visual studio ) highlights the line that I put between * *.
Related
import 'package:flutter/material.dart';
import 'package:google_maps_flutter/google_maps_flutter.dart';
import 'package:geolocator/geolocator.dart';
import 'dart:async';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
return MaterialApp(
home: MapSample(),
);
}
}
class MapSample extends StatefulWidget {
#override
State<MapSample> createState() => MapSampleState();
}
class MapSampleState extends State<MapSample> {
Future<Position> _determinePosition() async {
Position position = await Geolocator.getCurrentPosition();
return position;
}
late GoogleMapController googleMapController;
static final CameraPosition _kGooglePlex = CameraPosition(
target: LatLng(37.42796133580664, -122.085749655962),
zoom: 14.4746,
);
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text("Medical Location"),
centerTitle: true,
),
body: GoogleMap(
mapType: MapType.hybrid,
// markers: {_kGooglePlexMarker},
initialCameraPosition: _kGooglePlex,
onMapCreated: (GoogleMapController controller) {
googleMapController = controller;
},
),
floatingActionButton: FloatingActionButton.extended(
onPressed: () async {
Position position = await _determinePosition();
googleMapController.animateCamera(CameraUpdate.newCameraPosition(
CameraPosition(
target: LatLng(position.latitude, position.longitude),
zoom: 14)));
setState(() {});
},
label: Text('Current Location'),
icon: Icon(Icons.location_history),
),
);
}
}
Hello, this is the code I've been working on and it shows users' location on the map when they click the 'current location' button.
What I want to implement is to make the map shows nearby hospitals based on the user's current location. I've searched for documents about this problem but couldn't find one that really can help me. I'm getting the current location by 'LatLng(position.latitude, position.longitude)' which is not specific numbers fixed because location can vary.
I think I need to use 'places API' but except for that, I couldn't figure solutions out yet.
Could anyone help me to solve this problem by explaining codes I need to add?
Thank you so much
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.
I want to create a RIVE animation with flutter. I followed a tutorial in YouTube. I wrote the same thing but when I execute two errors is displayed
(RiveFile.import (data);
file.mainArtboard;)
Here is the code:
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:rive/rive.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
home: MyPage(),
);
}
}
class MyPage extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Using Rive'),
),
body: RocketContainer());
}
}
class RocketContainer extends StatefulWidget {
#override
_RocketContainerState createState() => _RocketContainerState();
}
class _RocketContainerState extends State<RocketContainer> {
Artboard _artboard;
RiveAnimationController _rocketController;
#override
void initState() {
_loadRiveFile();
super.initState();
}
void _loadRiveFile() async {
final bytes = await rootBundle.load('assets/rocket.riv');
final file = RiveFile.import(bytes);
setState(() {
_artboard = file.mainArtboard;
});
}
void _launch() async {
_artboard.addController(
_rocketController = SimpleAnimation('launch'),
);
setState(() => _rocketController.isActive = true);
}
void _fall() async {
_artboard.addController(
_rocketController = SimpleAnimation('fall'),
);
setState(() => _rocketController.isActive = true);
}
#override
Widget build(BuildContext context) {
return Column(
children: [
Container(
width: MediaQuery.of(context).size.width,
height: MediaQuery.of(context).size.height - 250,
child: _artboard != null
? Rive(
artboard: _artboard,
fit: BoxFit.cover,
)
: Container()),
TextButton(onPressed: () => _launch(), child: Text('launch')),
TextButton(onPressed: () => _fall(), child: Text('fall'))
],
);
}
}
errors:
The current Dart SDK version is 2.10.5.
Because animation depends on cupertino_icons >=1.0.1 which requires SDK version >=2.12.0-0 <3.0.0, version solving failed.
pub get failed (1; Because animation depends on cupertino_icons >=1.0.1 which requires SDK version >=2.12.0-0 <3.0.0, version solving failed.)
*error: Instance member 'import' can't be accessed using static access. (static_access_to_instance_member at [animation] lib\main.dart:47)
*error: The getter 'mainArtboard' isn't defined for the type 'bool'. (undefined_getter at [animation] lib\main.dart:50)
You could have a look at the example provided with the updated and latest documentation of Rive in their official Github repository.
Control playing and pausing a looping animation:
import 'package:flutter/material.dart';
import 'package:rive/rive.dart';
class PlayPauseAnimation extends StatefulWidget {
const PlayPauseAnimation({Key? key}) : super(key: key);
#override
_PlayPauseAnimationState createState() => _PlayPauseAnimationState();
}
class _PlayPauseAnimationState extends State<PlayPauseAnimation> {
// Controller for playback
late RiveAnimationController _controller;
// Toggles between play and pause animation states
void _togglePlay() =>
setState(() => _controller.isActive = !_controller.isActive);
/// Tracks if the animation is playing by whether controller is running
bool get isPlaying => _controller.isActive;
#override
void initState() {
super.initState();
_controller = SimpleAnimation('idle');
}
#override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: RiveAnimation.network(
'https://cdn.rive.app/animations/vehicles.riv',
controllers: [_controller],
// Update the play state when the widget's initialized
onInit: () => setState(() {}),
),
),
floatingActionButton: FloatingActionButton(
onPressed: _togglePlay,
tooltip: isPlaying ? 'Pause' : 'Play',
child: Icon(
isPlaying ? Icons.pause : Icons.play_arrow,
),
),
);
}
}
To play an animation from an asset bundle, use:
RiveAnimation.asset('assets/vehicles.riv'
in place of
RiveAnimation.network('https://cdn.rive.app/animations/vehicles.riv',
This line:
_controller = SimpleAnimation('idle');
attempts to play an animation called 'idle'. If your animation is named differently, try replacing the name here.
This is my storage. I want the image to shown on my app directly. THE REQUEST REACHES the storage, I checked from the statistics. But cannot take it, also I changed rules to that everyone can download them. But still nothing. I tried solutions from this page: Flutter Load Image from Firebase Storage
But they didn't work at all. Maybe I've put the codes in the wrong places, I don't know. How do I do this? Can you please help? Here's my whole code of main.dart:
import 'package:firebase_storage/firebase_storage.dart';
import 'package:flutter/material.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:firebase_core/firebase_core.dart';
void main() async {
WidgetsFlutterBinding.ensureInitialized();
await Firebase.initializeApp();
runApp(MyApp());
}
class MyApp extends StatelessWidget {
// This widget is the root of your application.
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.red,
visualDensity: VisualDensity.adaptivePlatformDensity,
),
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;
var url;
void _incrementCounter() {
setState(() {
_counter++;
});
}
Widget _buildListItem(BuildContext context, DocumentSnapshot document) {
String mezunD;
if (document.data()['mezunDurumu'] == false) {
mezunD = "mezun değil";
}
if (document.data()['mezunDurumu'] == true) {
mezunD = "mezun";
}
var listTile = ListTile(
title: Column(
children: [
Expanded(
child: Text(
"Ad Soyad: " + document.data()['adSoyad'],
),
),
Expanded(
child: Text(
"Yaş: " + document.data()['yas'].toString(),
),
),
Expanded(
child: Text(
"Doğum Tarihi: " + document.data()['dogumTarihi'],
),
),
Expanded(
child: Text("Mezun Durumu: " + mezunD),
),
//I wanna show image right under these.
],
),
);
return listTile;
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text("Öğrenci Durumu"),
),
body: StreamBuilder(
stream: FirebaseFirestore.instance.collection('tablo').snapshots(),
builder: (context, snapshot) {
if (!snapshot.hasData) return const Text('Loading...');
return ListView.builder(
itemExtent: 100.0,
itemCount: snapshot.data.documents.length,
itemBuilder: (context, index) =>
_buildListItem(context, snapshot.data.documents[index]),
);
}),
);
}
}
If you click in the firebase storage on the image then you can see on right side a preview of the image. under this preview is a blue link. if you tap on the blue link you open the image in full-size in the browser with the full image-address including the access-token. copy the full url of this browser window and use it in flutter. for example with:
Image.network(url);
or the package "cached_network_image"
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