无法使用条码扫描仪显示条码的内容

Question

我一直在尝试使用条码扫描仪显示商品的条码... 我已经编写了用于扫描条形码的代码，但由于它抛出错误而无法显示。此代码能够首先打开相机然后扫描条形码，直到这里它完全可以正常工作但是当我尝试显示条形码时它抛出异常。

import 'package:flutter/material.dart';
import 'dart:async';
import 'dart:io';
import 'package:barcode_scan/barcode_scan.dart';
import 'package:flutter/services.dart';


class CartItems extends StatefulWidget {
  @override
  _CartItemsState createState() => _CartItemsState();
}

class _CartItemsState extends State<CartItems> {

  String barcode = "";

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: SafeArea(child: Text('Code: ' + barcode)),
      floatingActionButton: FloatingActionButton(
        onPressed: barcodeScanning,
        child: Icon(Icons.add),
      ),
    );
  }

  Future barcodeScanning() async {
    try {
      String barcode = BarcodeScanner.scan() as String;
      setState(() => this.barcode = barcode);
    } on PlatformException catch (e) {
      if (e.code == BarcodeScanner.cameraAccessDenied) {
        setState(() {
          this.barcode = 'No camera permission!';
        });
      } else {
        setState(() => this.barcode = 'Unknown error: $e');
      }
    } on FormatException {
      setState(() =>
      this.barcode =
      'Nothing captured.');
    } catch (e) {
      setState(() => this.barcode = 'Unknown error: $e');
    }
  }
}

请调查我正在努力解决错误的问题。

Answer 1

传递扫描仪函数的返回结果。通过这种方式，函数执行并将其发现提供给主上下文，还添加一个 print() 以在底部查看结果以查看控制台中可能出现的异常

class CartItems extends StatefulWidget {
  @override
  _CartItemsState createState() => _CartItemsState();
}

class _CartItemsState extends State<CartItems> {

  String barcodeResult = "";
  String barcode = "";


  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: SafeArea(child: Text('Code: ' + barcode)),
      floatingActionButton: FloatingActionButton(
        onPressed:(){ barcodeScanning().then((value) 
       {
          setState(()
           {barcodeResult = value;})})}// this should work
        child: Icon(Icons.add),
      ),
    );
  }

  Future barcodeScanning() async {
    try {
      String barcode = BarcodeScanner.scan() as String;
      setState(() => this.barcode = barcode);
    } on PlatformException catch (e) {
      if (e.code == BarcodeScanner.cameraAccessDenied) {
        setState(() {
          this.barcode = 'No camera permission!';
        });
      } else {
        setState(() => this.barcode = 'Unknown error: $e');
      }
    } on FormatException {
      setState(() =>
      this.barcode =
      'Nothing captured.');
    } catch (e) {
      setState(() => this.barcode = 'Unknown error: $e');
    }
   return barcode;//this
  }
}

无法使用条码扫描仪显示条码的内容

Unable to display the contents of a barcode using barcode scanner

barcode-scanner

dart

flutter