I'm attempting to run location updates on a Flutter isolate thread, the error is only present when running an isolate. Location requests works without issues on the main thread. The goal here is to run this as a background service, working with dart code only.
I am using Geolocator plugin for location requests.
This is the error I am facing when starting the isolate:
Exception has occurred. FlutterError
(ServicesBinding.defaultBinaryMessenger was accessed before the
binding was initialized.
I have tried to include the WidgetsFlutterBinding.ensureInitialized() before runApp but without results.
Looking at the call stack of the error, it seems problems occur at the android location platform call: checkPermissionStatus
This happens regardless of what location plugin I am using, it stops at the permission status check.
I have figured it could have something to do with awaiting location permission user input, but this check will fail on a non-ui thread?
See this simple main.dart file for an example:
import 'dart:isolate';
import 'package:flutter/material.dart';
import 'package:geolocator/geolocator.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Isolate location test',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(title: 'Isolate location test'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
Isolate isolate;
bool isRunning = false;
String output = '';
ReceivePort receivePort;
void start() async {
receivePort = ReceivePort();
await Isolate.spawn(locationUpdate, receivePort.sendPort);
receivePort.listen((dynamic data) {
setState(() {
isRunning = true;
});
}, onDone: () {
print("done");
});
}
void stop() {
if (isolate != null) {
setState(() {
isRunning = false;
});
receivePort.close();
isolate.kill(priority: Isolate.immediate);
isolate = null;
}
}
static void locationUpdate(SendPort sendPort) async {
Geolocator().checkGeolocationPermissionStatus().then((status) {
sendPort.send(status);
});
// Geolocator().getCurrentPosition().then((pos) {
// sendPort.send(pos);
// });
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(child: Text(output)),
floatingActionButton: FloatingActionButton(
onPressed: isRunning ? stop : start,
child: Icon(isRunning ? Icons.stop : Icons.play_circle_filled),
),
);
}
}
Related
We're building an Obstacle Detection System for visually impared person using mobile camera for college project.
I've made a simple camera app. How to find the focal length of android camera in this app? My
teacher assigned me this task but since i'm not well familiar in flutter. However i made a simple camera app through the help of internet.
I want someone to help me out find the focal length of the android camera. The source code of my camera app is:
// import 'dart:io';
import 'package:camera/camera.dart';
import 'package:flutter/material.dart';
Future<void> main() async {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
home: Home(),
);
}
}
class Home extends StatefulWidget {
#override
_HomeState createState() => _HomeState();
}
class _HomeState extends State<Home> {
List<CameraDescription>? cameras;
CameraController? controller;
// XFile? image; //for caputred image
#override
void initState() {
loadCamera();
super.initState();
}
loadCamera() async {
cameras = await availableCameras();
if (cameras != null) {
controller = CameraController(cameras![0], ResolutionPreset.max);
//cameras[0] = first camera, change to 1 to another camera
controller!.initialize().then((_) {
if (!mounted) {
return;
}
setState(() {});
});
} else {
print("No any camera found");
}
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text("DRISTI"),
backgroundColor: Color(0xFF2899bd),
),
body: Container(
child: Column(children: [
Container(
child: controller == null
? Center(child: Text("Loading Camera..."))
: !controller!.value.isInitialized
? Center(
child: CircularProgressIndicator(),
)
: CameraPreview(controller!)),
])),
);
}
}
Use the CameraDescription class provided by the camera package
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.
I'm having a problem with my app.
The situation is: i have a very simple login system on the app and i save the logged user using SharedPreferences.
But if the user leaves the app and then return it will open the login screen again, so i want to skip the login screen if the user is logged.
So in my main i put a function to check if there is login information, if yes it would redirect right to the app page or to the login page if not.
But when i try to call the app page it always calls the page setted on the Home part.
How can i solve this?
Is there any way to make it ignore the Home?
Is there a way to make the "if" part on the home? Would be the better solution but its not possible.
Also i know i'm not using the best way to make this control, but it works (despite of this problem i have now, sure) and if you have any tips on making it better i would appreciate.
Heres my code:
class MyApp extends StatefulWidget {
#override
_MyAppState createState() => _MyAppState();
}
void main() => runApp(new MyApp());
class _MyAppState extends State<MyApp> {
Future<void> verificaLogin() async {
print("running ok"); //just to test if the function runs
final prefs = await SharedPreferences.getInstance();
final key = 'usuario';
final value = prefs.getString(key);
print('saved tester $value');
String usu = value; /
if (usu.isEmpty) {
BuildContext context;
Navigator.push(
context,
MaterialPageRoute(builder: (context) => LoginScreen()), //sends to loginscreen if not logged
);
}
if (usu.isNotEmpty) {
BuildContext context;
Navigator.of(context)
.pushReplacement(MaterialPageRoute(builder: (context) => Pedidos())); //sends to main (not main.dart) app page
}
}
#override
void initState() {
super.initState();
WidgetsBinding.instance.addPostFrameCallback((_) => verificaLogin());
}
Widget build(BuildContext context) {
return BotToastInit(
child: MaterialApp(
navigatorObservers: [BotToastNavigatorObserver()],
title: "Test App",
theme: ThemeData(
primarySwatch: Colors.green,
),
debugShowCheckedModeBanner: false,
home: LoginScreen(), //i'm calling the loginscreen, it ignores the function on the top
),
);
}
}
Please make one SplashScreen like below it resolves your issue..
and call this as home: SplashScreen(),
class SplashScreen extends StatefulWidget {
#override
_SplashScreenState createState() => _SplashScreenState();
}
class _SplashScreenState extends State<SplashScreen> {
String loginData = "";
SharedPreferences sharedPreferences;
void initState() {
super.initState();
readFromStorage();
}
void readFromStorage() async {
sharedPreferences = await SharedPreferences.getInstance();
final key = 'usuario';
loginData = sharedPreferences.getString(key);
if (loginData.isNotEmpty) {
Future.delayed(const Duration(milliseconds: 3000), () {
setState(() {
Navigator.of(context)
.pushReplacement(MaterialPageRoute(builder: (context) => Pedidos()));
});
});
} else {
Future.delayed(const Duration(milliseconds: 3000), () {
setState(() {
Navigator.push(
context,
MaterialPageRoute(builder: (context) => LoginScreen()),);
});
});
}
}
#override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
FlutterLogo(
size: 100.0,
),
],
)),
);
}
}
Hi you can use a FutureBuilder at vefiricaLoigin, and then Material App at home use verificaLogin,
https://api.flutter.dev/flutter/widgets/FutureBuilder-class.html
verificaLogin() {
return FutureBuilder<Widget>(
future: SharedPreferences.getInstance(),
builder: (BuildContext context, prefs) {
final key = 'usuario';
final value = prefs.getString(key);
String usu = value;
if (usu.isEmpty) {
return LoginScreen()l
} else {
return Pedidos();
}
);
}
Widget build(BuildContext context) {
return MaterialApp(
title: "Test App",
theme: ThemeData(
primarySwatch: Colors.green,
),
debugShowCheckedModeBanner: false,
home: verificaLogin()
);
}
Code I show you is the simplified code which I'm troubled in.
My expected result is [1,2,3,4,5,6], but app says [1,2,3].
I know "loadMoreInterger()" should be in "initState()", but for some reason I have to put it in Widget build() {"HERE"}.
I wonder if why doesn't it work, and the solution for correct result.....
I really appreciate for your help :)
import 'package:flutter/material.dart';
import 'dart:async';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
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();
}
// ↓↓↓↓↓↓↓↓↓↓↓WHERE I CANNOT UNDERSTAND↓↓↓↓↓↓↓↓↓↓↓
class _MyHomePageState extends State<MyHomePage> {
List<int> intList = [1,2,3];
Future<List<int>> loadMoreInteger() async {
print('Future');
return [4,5,6];
}
#override
Widget build(BuildContext context) {
loadMoreInteger().then((value) {
intList.addAll(value); // why doesn't it work?
});
print("console: $intList");
return Scaffold(
body: Center(
child: Text("display: $intList")
)
);
}
}
//Expected result: [1,2,3,4,5,6]
//Actual result: [1,2,3]
put it in initState override function and it works for yu !!!!
List<int> intList = new List();
Future<List<int>> loadMoreInteger() async {
print('Future');
return [4,5,6];
}
#override
void initState() {
super.initState();
intList = [1,2,3];
loadMoreInteger().then((v){
setState(() {
intList.addAll(v) ;
});
}); }
Here is what your build method does: after entering the method it starts to execute loadMoreInteger() future. Afterwards even if executed future is synchronous it only schedules call of next future that is produced by calling .then. So build method continues to execute with old intList value. And [4,5,6] will be added only after build completes.
In general you can wait for future to complete by calling it with await keyword. But build method is overriden and already has predefined return type that is not future, so you can not call await inside build.
What you can do:
I highly recommend moving any manipulation with data from build method. Its purpose is to produce widgets as fast as possible. It can be called multiple times at some moment unexpected for developer.
One of possible options for you will be moving loadMoreInteger() to initState and calling setState when intList is updated
#override
void initState() {
super.initState();
loadMoreInteger().then((value) {
setState(() {
intList.addAll(value);
});
});
}
I'm trying to Play a custom mp3 sound I've put in an asset folder into the app folder, like you would do for a font or an image file, but then I don't really know how to proceed. I think I might need to register the audio file into the pubspec.yaml, but how?
And how do I play it?
I've checked out this two answer:
How to play a custom sound in Flutter?
Flutter - Play custom sounds updated?
But the first one is too old and the second one uses URLs as the sound path: const kUrl2 = "http://www.rxlabz.com/labz/audio.mp3"; and the sound I like to play is in the app, not online. So... How can I do it?
This Is My Current Code, as You can see, there's only a Floating Button.
And I need To Start The Sound at the Point I stated it in the code.
But visual studio underlines in red Various Parts:
await: it says that await is unrecognized.
audioPlugin.play: is says It's also unrecognized
import 'dart:io';
import 'dart:typed_data';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
void main() => runApp(new MyApp());
Directory tempDir = await getTemporaryDirectory();
File tempFile = new File('${tempDir.path}/demo.mp3');
await tempFile.writeAsBytes(bytes, flush: true);
AudioPlayer audioPlugin = new AudioPlayer();
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return new MaterialApp(
title: 'Flutter Demo',
theme: new ThemeData(
primarySwatch: Colors.blue,
),
home: new MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
#override
_MyHomePageState createState() => new _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
void _incrementCounter() {
setState(() {
print("Button Pressed");
///
///
///
/// Here I Need To start Playing the Sound
///
///
///
///
audioPlugin.play(tempFile.uri.toString(), isLocal: true);
});
}
#override
Widget build(BuildContext context) {
return new Scaffold(
appBar: new AppBar(
title: new Text(widget.title),
),
body: new Center(),
floatingActionButton: new FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: new Icon(Icons.add),
),
);
}
}
It's not pretty, but...
Add the mp3 file to the assets folder and add it to pubspec.yaml like this.
Load the asset as binary data with rootBundle.load(asset)
Use path_provider to get the app's temp folder location
Use regular dart:io to open a file in tempDir (maybe use the asset name) and write bytes to it.
Form a file URL from the temporary file name in the form file:///folderPath/fileName
Pass this to audioplayer, setting isLocal to true (needed on iOS).
import 'dart:async';
import 'dart:io';
import 'dart:typed_data';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:audioplayer/audioplayer.dart';
import 'package:path_provider/path_provider.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Audio Player Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: const MyHomePage(),
);
}
}
class MyHomePage extends StatefulWidget {
const MyHomePage({Key key}) : super(key: key);
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
AudioPlayer audioPlugin = AudioPlayer();
String mp3Uri;
#override
void initState() {
_load();
}
Future<Null> _load() async {
final ByteData data = await rootBundle.load('assets/demo.mp3');
Directory tempDir = await getTemporaryDirectory();
File tempFile = File('${tempDir.path}/demo.mp3');
await tempFile.writeAsBytes(data.buffer.asUint8List(), flush: true);
mp3Uri = tempFile.uri.toString();
print('finished loading, uri=$mp3Uri');
}
void _playSound() {
if (mp3Uri != null) {
audioPlugin.play(mp3Uri, isLocal: true);
}
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Audio Player Demo Home Page'),
),
body: Center(),
floatingActionButton: FloatingActionButton(
onPressed: _playSound,
tooltip: 'Play',
child: const Icon(Icons.play_arrow),
),
);
}
}
Use the audioplayers package => https://pub.dev/packages/audioplayers
Add the key to plist for iOS Support
<key>NSAppTransportSecurity</key>
<dict>
<key>NSAllowsArbitraryLoads</key>
<true/>
</dict>
Add dependencies to pubspec.yaml file
audioplayers: ^0.13.2
Flutter code:
import 'package:flutter/material.dart';
import 'package:audioplayers/audio_cache.dart';
import 'package:audioplayers/audioplayers.dart';
class AudioTest extends StatefulWidget {
#override
_AudioTestState createState() => _AudioTestState();
}
class _AudioTestState extends State<AudioTest> {
static AudioCache _player = AudioCache();
static const _audioPath = "count_down.mp3";
AudioPlayer _audioPlayer = AudioPlayer();
Future<AudioPlayer> playAudio() async {
return _player.play(_audioPath);
}
void _stop(){
if (_audioPlayer != null) {
_audioPlayer.stop();
}
#override
void initState() {
playAudio().then((player) {
_audioPlayer = player;
});
super.initState();
}
#override
Widget build(BuildContext context) {
return homeScreen();
}
Widget homeScreen() {
return Scaffold();
//Enter your code here
}
}