I am working on a project using OpenCV. I already created a python "prototype". Now I'd like to move it to Flutter. This is where I encountered a few problems.
I imported the https://pub.dev/packages/opencv flutter package.
import "package:opencv/opencv.dart";
import 'package:opencv/core/core.dart';
import 'dart:io';
import 'dart:async';
Future<void> main() async {
var url = "/sdcard/Download/test5.png";
var myFile = await File(url).readAsBytes();
print(myFile);
print(await ImgProc.medianBlur(myFile, 5));
}
After I run this code I get this error:
E/flutter (10044): [ERROR:flutter/lib/ui/ui_dart_state.cc(199)] Unhandled Exception: Null check operator used on a null value
E/flutter (10044): #0 MethodChannel.binaryMessenger (package:flutter/src/services/platform_channel.dart:142:86)
E/flutter (10044): #1 MethodChannel._invokeMethod (package:flutter/src/services/platform_channel.dart:148:36)
E/flutter (10044): #2 MethodChannel.invokeMethod (package:flutter/src/services/platform_channel.dart:331:12)
E/flutter (10044): #3 ImgProc.medianBlur (package:opencv/core/imgproc.dart:539:43)
E/flutter (10044): #4 main (package:projectgama/opencvTest.dart:19:23)
E/flutter (10044): <asynchronous suspension>
E/flutter (10044):
Does anybody know what I'm doing wrong? Did anybody manage to work with OpenCV in Flutter?
Related
I have this code below which plays a sound every time I hit a button.
AudioPlayer player = AudioPlayer();
Future<void> playSound({required String soundStr}) async {
player.setAsset(soundStr);
player.play();
}
But whenever I hit the button fast, sometimes it will show this error. How can I eliminate this error? I tried adding player.stop(); but it still the same.
E/flutter ( 4312): [ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: PlatformException(abort, Loading interrupted, null, null)
E/flutter ( 4312): #0 AudioPlayer._setPlatformActive.checkInterruption (package:just_audio/just_audio.dart:1236:7)
E/flutter ( 4312): #1 AudioPlayer._setPlatformActive.setPlatform (package:just_audio/just_audio.dart:1347:11)
E/flutter ( 4312): <asynchronous suspension>
E/flutter ( 4312):
E/flutter ( 4312): [ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: PlatformException(abort, Loading interrupted, null, null)
E/flutter ( 4312):
Edit: I tried adding await.
Future<void> playSound({required String soundStr}) async {
await player.setAsset(soundStr);
await player.play();
}
If I hit the buttons fast, it will still have error. Though it is now different.
E/flutter (21654): [ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: Connection aborted
E/flutter (21654): #0 AudioPlayer._load (package:just_audio/just_audio.dart:843:11)
E/flutter (21654): <asynchronous suspension>
E/flutter (21654): #1 AudioPlayer.load (package:just_audio/just_audio.dart:770:14)
E/flutter (21654): <asynchronous suspension>
E/flutter (21654): #2 AudioPlayer.setAudioSource (package:just_audio/just_audio.dart:745:18)
E/flutter (21654): <asynchronous suspension>
E/flutter (21654): #3 playSound (package:super_pinoy_quiz/common/generic_methods.dart:396:3)
E/flutter (21654): <asynchronous suspension>
E/flutter (21654):
I'm using this package: just_audio: ^0.9.29
Though I tried using different package but it also encounters the same error when hitting the button fast: audioplayers: ^1.1.1
Both setAsset and play are future method, you can await for setting assets
Future<void> playSound({required String soundStr}) async {
await player.setAsset(soundStr);
await player.play();
}
I have my flutter App integrated with firebase, everything was fine but after i integrate firebase i got error whenever I try to run my app.
My main method looks like this:
Future<void> main() async {
WidgetsFlutterBinding.ensureInitialized();
await Firebase.initializeApp(
options: DefaultFirebaseOptions.currentPlatform,
);
runApp(child: MyApp());
}
Error:
E/flutter ( 7922): [ERROR:flutter/lib/ui/ui_dart_state.cc(209)] Unhandled Exception:
PlatformException(firebase_core, FirebaseApp name [DEFAULT] already exists!, null, null)
E/flutter ( 7922): #0 StandardMethodCodec.decodeEnvelope
(package:flutter/src/services/message_codecs.dart:607:7)
E/flutter ( 7922): #1 MethodChannel._invokeMethod
(package:flutter/src/services/platform_channel.dart:177:18)
E/flutter ( 7922): <asynchronous suspension>
E/flutter ( 7922): #2 MethodChannel.invokeMapMethod
(package:flutter/src/services/platform_channel.dart:377:43)
E/flutter ( 7922): <asynchronous suspension>
E/flutter ( 7922): #3 MethodChannelFirebase.initializeApp (package:firebase_core_platform_interface/src/method_channel/method_channel_firebase.dart:100:40)
E/flutter ( 7922): <asynchronous suspension>
E/flutter ( 7922): #4 Firebase.initializeApp
(package:firebase_core/src/firebase.dart:40:31)
E/flutter ( 7922): <asynchronous suspension>
E/flutter ( 7922): #5 main (package:zunada/main.dart:11:3)
E/flutter ( 7922): <asynchronous suspension>
E/flutter ( 7922):
I had similar issue when create firebase app by flavors using flutterfire CLI. I realized that flutterfire create apps with same name in different projects. Then I tried 2 ways and it works.
1st: manually change app name in each firebase project.
2nd: add param name when initialize such as in main_dev.dart
Example:
await Firebase.initializeApp(
name: "dev-project",
options: DefaultFirebaseOptions.currentPlatform);
I used the same name used in the firebase console as my project ID for consistency, keep in mind that you cannot add spaces to the name (only dashes -).
i already initialized awesome_notifications plugin in main.dart When i hot restart, in debug console i'm getting this error:
E/flutter ( 4447): [ERROR:flutter/lib/ui/ui_dart_state.cc(198)] Unhandled Exception: MissingPluginException(No implementation found for method initialize on channel awesome_notifications)
E/flutter ( 4447): #0 MethodChannel._invokeMethod
package:flutter/…/services/platform_channel.dart:165
E/flutter ( 4447): <asynchronous suspension>
E/flutter ( 4447): #1 AwesomeNotifications.initialize (package:awesome_notifications/src/awesome_notifications_core.dart:174:18)
E/flutter ( 4447): <asynchronous suspension>
E/flutter ( 4447):
E/flutter ( 4447): [ERROR:flutter/lib/ui/ui_dart_state.cc(198)] Unhandled Exception: MissingPluginException(No implementation found for method isNotificationAllowed on channel awesome_notifications)
E/flutter ( 4447): #0 MethodChannel._invokeMethod
package:flutter/…/services/platform_channel.dart:165
E/flutter ( 4447): <asynchronous suspension>
Here's my code :
main.dart
Future<void> main() async {
WidgetsFlutterBinding();
await Hive.initFlutter();
if (!Hive.isAdapterRegistered(AddEventModelAdapter().typeId)) {
Hive.registerAdapter(AddEventModelAdapter());
}
AwesomeNotifications()
.initialize('resource://drawable/res_notification_app_icon', [
NotificationChannel(
channelKey: 'schedule_channel',
channelName: 'scheduled_channel',
channelDescription: 'descroiption',
locked: true,
importance: NotificationImportance.High,
),
]);
runApp(const MyApp());
}
Whenever you add a plugin in your pubspec.yaml, you need to stop the app and re-run it again because the plugin contains native code on both platforms.
If it still does not work, then do flutter clean and run.
I am trying to implement the twilio_voice: ^0.0.9 plug in and register my firebase app at the same time but, when I run my registration function I get the error:
E/flutter (27321): [ERROR:flutter/lib/ui/ui_dart_state.cc(209)] Unhandled Exception: [firebase_functions/not-found] NOT_FOUND
E/flutter (27321):
E/flutter (27321): #0 StandardMethodCodec.decodeEnvelope
package:flutter/…/services/message_codecs.dart:607
E/flutter (27321): #1 MethodChannel._invokeMethod
package:flutter/…/services/platform_channel.dart:156
E/flutter (27321): <asynchronous suspension>
E/flutter (27321): #2 MethodChannelHttpsCallable.call
package:cloud_functions_platform_interface/…/method_channel/method_channel_https_callable.dart:23
E/flutter (27321): <asynchronous suspension>
E/flutter (27321): #3 HttpsCallable.call
package:cloud_functions/src/https_callable.dart:35
E/flutter (27321): <asynchronous suspension>
E/flutter (27321): #4 _TextScreenState.register
package:buddiesDrivers/CallScreen/TextScreen.dart:72
E/flutter (27321): <asynchronous suspension>
E/flutter (27321):
E/flutter (27321): #0 MethodChannelHttpsCallable.call
package:cloud_functions_platform_interface/…/method_channel/method_channel_https_callable.dart:39
E/flutter (27321): <asynchronous suspension>
E/flutter (27321): #1 HttpsCallable.call
package:cloud_functions/src/https_callable.dart:35
E/flutter (27321): <asynchronous suspension>
I am have firebase implemented and running and I am getting my token when logging in. The app seems to fail when calling the httpsCallable("voice-accessToken") in the app. Here is the function:
register() async {
print("voip-registtering with token ");
print("voip-calling voice-accessToken");
final function =
FirebaseFunctions.instance.httpsCallable("voice-accessToken");
final data = {
"platform": Platform.isIOS ? "iOS" : "Android",
};
final result = await function.call(data);
print("voip-result");
print(result.data);
String androidToken;
if (Platform.isAndroid) {
androidToken = await FirebaseMessaging.instance.getToken();
print("androidToken is " + androidToken);
}
TwilioVoice.instance
.setTokens(accessToken: result.data, deviceToken: androidToken);
}
Any help in the right direction would be appreciated
I'm using Dio in my app and I want it to save cookies. It turns out I have to download three additional packages to do that: cookie_jar, dio_cookie_manager and path_provider.
I need to:
get application document directory:
Directory docDir = await getApplicationDocumentsDirectory();
pass it to PersistCookieJar
PersistCookieJar(storage: FileStorage(appDocDir.path + '/.cookies/'));
and add it to interceptors:
dio.interceptors.add(CookieManager(_cookieJar));
My problem is with the first part. For some reason, getApplicationDocumentsDirectory(); throws an error when not used inside a StatefulWidget widget.
I have two questions:
Why on earth would getting a path require a StatefulWidget?
How can I do what I want? I need to initialize Dio as early as possible so that by the time the UI loads, the user is already (or almost) logged in. Plus, I don't want to put the logic of initiating the client object inside the UI code, that might for example cause it to be initiated multiple times whenever the widget is created.
What my code looks like right now:
Future<void> initStuff() async {
initLocator();
Directory docDir = await getApplicationDocumentsDirectory(); // throws
print('docDir = ${docDir.path}');
Client cli = Client(docDir);
locator.registerSingleton<Client>(cli);
// ...
}
void main() async {
await initStuff();
runApp(MyApp());
}
Client constructor:
Client(Directory appDocDir) {
final _cookieJar = PersistCookieJar(storage: FileStorage(appDocDir.path + '/.cookies/'));
dio = Dio()
..options.baseUrl = Utils.SERVER_ADDRESS
..options.sendTimeout = 5000
..options.receiveTimeout = 5000
..options.connectTimeout = 5000
..interceptors.add(CookieManager(_cookieJar));
}
The error I'm getting:
E/flutter (24953): [ERROR:flutter/lib/ui/ui_dart_state.cc(199)] Unhandled Exception: Null check operator used on a null value
E/flutter (24953): #0 MethodChannel.binaryMessenger
package:flutter/…/services/platform_channel.dart:142
E/flutter (24953): #1 MethodChannel._invokeMethod
package:flutter/…/services/platform_channel.dart:148
E/flutter (24953): #2 MethodChannel.invokeMethod
package:flutter/…/services/platform_channel.dart:331
E/flutter (24953): #3 MethodChannelPathProvider.getApplicationDocumentsPath
package:path_provider_platform_interface/src/method_channel_path_provider.dart:50
E/flutter (24953): #4 getApplicationDocumentsDirectory
package:path_provider/path_provider.dart:138
E/flutter (24953): #5 initStuff
package:proj/main.dart:20
E/flutter (24953): #6 main
package:proj/main.dart:63
E/flutter (24953): #7 _runMainZoned.<anonymous closure>.<anonymous closure> (dart:ui/hooks.dart:142:25)
E/flutter (24953): #8 _rootRun (dart:async/zone.dart:1354:13)
E/flutter (24953): #9 _CustomZone.run (dart:async/zone.dart:1258:19)
E/flutter (24953): #10 _runZoned (dart:async/zone.dart:1789:10)
E/flutter (24953): #11 runZonedGuarded (dart:async/zone.dart:1777:12)
E/flutter (24953): #12 _runMainZoned.<anonymous closure> (dart:ui/hooks.dart:138:5)
E/flutter (24953): #13 _delayEntrypointInvocation.<anonymous closure> (dart:isolate-patch/isolate_patch.dart:283:19)
E/flutter (24953): #14 _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:184:12)
OK: Thank you for updating your post.
The error is: Unhandled Exception: Null check operator used on a null value
It's coming from the 3rd party library call getApplicationDocumentsDirectory(), and it's occurring because you're calling a (currently uninitialized) value with null-safety enabled (a Good Thing!).
SUGGESTIONS:
Using a StatefulWidget is a bit more work - but it makes sense here. It also happens to resolve the problem for you, correct?
You might try making docDir nullable (e.g. String? path). This is exactly what the getApplicationDocument page shows:
https://pub.dev/documentation/path_provider/latest/path_provider/getApplicationDocumentsDirectory.html
Future<Directory> getApplicationDocumentsDirectory() async {
final String? path = await _platform.getApplicationDocumentsPath();
if (path == null) {
throw MissingPlatformDirectoryException(
'Unable to get application documents directory');
}
return Directory(path);
}
Finally, check out these links:
https://stackoverflow.com/a/67990442/421195
https://stackoverflow.com/a/68876902/421195
Run this in main() before everything else:
WidgetsFlutterBinding.ensureInitialized();