flutter zxing2 扫描仪示例

问题描述 投票：0回答：2

flutter Zxing2 pub 包有任何工作示例吗？我确实尝试了官方的 pub 包示例 [https://pub.dev/packages/zxing2/example | Dart包]但是不起作用。我收到以下错误

I/CameraManagerGlobal( 5452): Connecting to camera service
E/flutter ( 5452): [ERROR:flutter/lib/ui/ui_dart_state.cc(213)] Unhandled Exception: CameraException(Uninitialized CameraController, startImageStream() was called on an uninitialized CameraController.)
E/flutter ( 5452): #0      CameraController._throwIfNotInitialized (package:camera/src/camera_controller.dart:769:7)
E/flutter ( 5452): #1      CameraController.startImageStream (package:camera/src/camera_controller.dart:370:5)
E/flutter ( 5452): #2      _MyHomePageState._onCameraSelected (package:test_camera/main.dart:83:26)
E/flutter ( 5452): #3      _MyHomePageState.initState (package:test_camera/main.dart:46:5)
E/flutter ( 5452): #4      StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:4796:57)
E/flutter ( 5452): #5      ComponentElement.mount (package:flutter/src/widgets/framework.dart:4631:5)
E/flutter ( 5452): #6      Element.inflateWidget (package:flutter/src/widgets/framework.dart:3666:14)
E/flutter ( 5452): #7      Element.updateChild (package:flutter/src/widgets/framework.dart:3418:18)
E/flutter ( 5452): #8      SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:6186:14)
E/flutter ( 5452): #9      Element.inflateWidget (package:flutter/src/widgets/framework.dart:3666:14)
E/flutter ( 5452): #10     Element.updateChild (package:flutter/src/widgets/framework.dart:3418:18)
E/flutter ( 5452): #11     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4683:16)
E/flutter ( 5452): #12     Element.rebuild (package:flutter/src/widgets/framework.dart:4348:5)
E/flutter ( 5452): #13     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:4636:5)
E/flutter ( 5452): #14     ComponentElement.mount (package:flutter/src/widgets/framework.dart:4631:5)
E/flutter ( 5452): #15     Element.inflateWidget (package:flutter/src/widgets/framework.dart:3666:14)
E/flutter ( 5452): #16     Element.updateChild (package:flutter/src/widgets/framework.dart:3418:18)
E/flutter ( 5452): #17     SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:6186:14)
E/flutter ( 5452): #18     Element.inflateWidget (package:flutter/src/widgets/framework.dart:3666:14)
E/flutter ( 5452): #19     Element.updateChild (package:flutter/src/widgets/framework.dart:3418:18)
E/flutter ( 5452): #20     SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:6186:14)
E/flutter ( 5452): #21     Element.inflateWidget (package:flutter/src/widgets/framework.dart:3666:14)
E/flutter ( 5452): #22     Element.updateChild (package:flutter/src/widgets/framework.dart:3418:18)
E/flutter ( 5452): #23     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4683:16)
E/flutter ( 5452): #24     StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4831:11)
E/flutter ( 5452): #25     Element.rebuild (package:flutter/src/widgets/framework.dart:4348:5)
E/flutter ( 5452): #26     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:4636:5)
E/flutter ( 5452): #27     StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:4822:11)
E/flutter ( 5452): #28     ComponentElement.mount (package:flutter/src/widgets/framework.dart:4631:5)
E/flutter ( 5452): #29     Element.inflateWidget (package:flutter/src/widgets/framework.dart:3666:14)
E/flutter ( 5452): #30     Element.updateChild (package:flutter/src/widgets/framework.dart:3418:18)
E/flutter ( 5452): #31     SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:6186:14)
E/flutter ( 5452): #32     Element.inflateWidget (package:flutter/src/widgets/framework.dart:3666:14)
E/flutter ( 5452): #33     Element.updateChild (package:flutter/src/widgets/framework.dart:3418:18)
E/flutter ( 5452): #34     SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:6186:14)
E/flutter ( 5452): #35     Element.inflateWidget (package:flutter/src/widgets/framework.dart:3666:14)
E/flutter ( 5452): #36     Element.updateChild (package:flutter/src/widgets/framework.dart:3418:18)
E/flutter ( 5452): #37     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4683:16)
E/flutter ( 5452): #38     StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4831:11)
E/flutter ( 5452): #39     Element.rebuild (package:flutter/src/widgets/framework.dart:4348:5)
E/flutter ( 5452): #40     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:4636:5)
E/flutter ( 5452): #41     StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:4822:11)
E/flutter ( 5452): #42     ComponentElement.mount (package:flutter/src/widgets/framework.dart:4631:5)
E/flutter ( 5452): #43     Element.inflateWidget (package:flutter/src/widgets/framework.dart:3666:14)
E/flutter ( 5452): #44     Element.updateChild (package:flutter/src/widgets/framework.dart:3418:18)
E/flutter ( 5452): #45     C

引发错误的代码位于第 83 行。

有人遇到同样的问题吗？如果有人给我一个使用 zxing2 的良好工作示例，我将非常感激。

注意：我只需要使用zxing2而不是qr或条形码扫描仪

谢谢

flutter dart zxing
2个回答
0
投票

我通过添加调用修复了这个错误 

await controller.initialize();
之前
unawaited(controller.startImageStream((image) {
采用 
_onCameraSelected
方法。

但是这个例子不包含zxing2的用法...

0
投票

我知道这很旧，但没有一个好的答案。我可以回答问题的两部分：

import 'package:zxing2/qrcode.dart';
import 'package:image/image.dart' as img;

...

class _QrCodeScannerState extends State<QrCodeScanner> {
  CameraController? controller;
  List<CameraDescription>? cameras;

  @override
  void initState() {
    super.initState();
    initializeCamera();  // this is fire and forget
  }

  Future<void> initializeCamera() async {
    cameras = await availableCameras();   // get available cameras
    if (cameras!.isNotEmpty) {
      controller = CameraController(cameras!.first, ResolutionPreset.high, imageFormatGroup: ImageFormatGroup.jpeg);
      await controller!.initialize();
      if (mounted) {
        setState(() {});  // we can now show the preview
        controller!.startImageStream(onLatestImage);    // and can start the imageStream
      }
    }
  }

  void onLatestImage(CameraImage image) {
    try {
      final barcode = decode(image.planes.first.bytes);
      print('$barcode');
    } catch (e) {
      print('Failed to decode image');
    }
  }

String decode(Uint8List fileBytes) {
  final image = img.decodeImage(fileBytes)!;

  LuminanceSource source = RGBLuminanceSource(
    image.width,
    image.height,
    image
      .convert(numChannels: 4)
      .getBytes(order: img.ChannelOrder.rgba)
      .buffer
      .asInt32List());
  final bitmap = BinaryBitmap(HybridBinarizer(source));
  final reader = QRCodeReader();
  return reader.decode(bitmap).text;
}

@override
Widget build(BuildContext context) {
  if (controller  == null || !controller!.value.isInitialized) {
    // important as we have to wait for the CameraController to be initialised
    return const Center(child: CircularProgressIndicator());
  }

  return Scaffold(
    body: Center(
      child: CameraPreview(controller!),
    ),
  );
}

上面确实回答了第一部分——CameraController的正确使用以及获取CameraImage，以及最后的过去——如何使用zxing2扫描图像。但是，我不能保证回答了从 CameraImage 到 zxing2 能理解的图像转换的问题。

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