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flutter - 无法使用条码扫描器显示条码的内容

问题描述

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码的代码，但由于引发错误而无法显示。该代码能够首先打开相机然后扫描条形码直到这里它工作得很好但是当我试图显示条形码时它会抛出一个异常。

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。

标签： flutterdartbarcode-scanner

解决方案

传递从您的扫描仪函数返回的结果。通过这种方式，函数执行并将其发现提供给主上下文，还添加了一个 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
  }
}

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