Xamarin.Forms QR Code Scan 二维码扫描的Android App

环境配置

VS2017
Xamarin.Forms .Net Standard 2.0

具体实现使用的是一个老项目了「ZXing.Net.Mobile」：https://github.com/Redth/ZXing.Net.Mobile

1. 新建项目 | QrCode3 & QrCode3.Android

新建项目如下图。（iOS应用不进行开发，具体操作详情请参考上文连接）

2. 添加 NuGet 包 | QrCode3 & QrCode3.Android

3. 添加 Android 权限 | QrCode3.Android

可另行添加闪光灯权限： FLASHLIGHT

4. MainActivity 初始化 | QrCode3.Android

MainActivity 中的 OnCreate 函数中添加代码:

MobileBarcodeScanner.Initialize(this.Application);

5. 添加接口 interface IQrCodeScanningService | QrCode3

namespace QrCode3.Service
{
    public interface IQrCodeScanningService
    {
  Task<string> ScanAsync();
 }
}

6. 实现接口 QrCodeScanningService | QrCode3.Android

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using Android.App;
using Android.Content;
using Android.OS;
using Android.Runtime;
using Xamarin.Forms;
using QrCode3.Service;
using ZXing.Mobile;
using System.Threading.Tasks;

[assembly: Dependency(typeof(QrCode3.Droid.Services.QrCodeScanningService))]

namespace QrCode3.Droid.Services
{
 public class QrCodeScanningService : IQrCodeScanningService
 {
  public async Task<string> ScanAsync()
  {
   var optionsDefault = new MobileBarcodeScanningOptions();
   var optionsCustom = new MobileBarcodeScanningOptions()
   {
    //UseFrontCameraIfAvailable = true,
    //Check diferents formats in http://barcode.tec-it.com/en
    // PossibleFormats = new List<ZXing.BarcodeFormat> {  ZXing.BarcodeFormat.CODE_128 }
   };
   var scanner = new MobileBarcodeScanner()
   {
    TopText = "对准二维码 / 条形码",
    BottomText = "触摸屏幕来聚焦"
   };

   var scanResults = await scanner.Scan(optionsCustom);

   //Fix by Ale 2017-07-06
   return (scanResults != null) ? scanResults.Text : string.Empty;
  }

 }
}

7. 修改主页面并添加调用的按钮 | QrCode3

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:local="clr-namespace:QrCode3"
             x:Class="QrCode3.MainPage">

    <StackLayout>
  <!-- Place new controls here -->
  <Button Text="Start" x:Name="btnScan" />
  <Entry x:Name="barcode" Placeholder="Todo" />
  <Button Text="打开扫描页面" x:Name="btnScan2" Clicked="BtnScan2_Clicked"/>
  <Label Text="Welcome to Xamarin.Forms!" 
           HorizontalOptions="Center"
           VerticalOptions="CenterAndExpand" />
    </StackLayout>

</ContentPage>

  private async void BtnScan_Clicked(object sender, EventArgs e)
  {
   var scanner = DependencyService.Get<IQrCodeScanningService>();
   var result = await scanner.ScanAsync();
   if(result != null)
    barcode.Text = result;
  }

8. 添加自定义扫描页面并调用 | QrCode3

自定义页面参考 https://gist.github.com/jfversluis/8e9acedafc3ef3fd6e279d9ccf08ff53

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
    xmlns:zxing="clr-namespace:ZXing.Net.Mobile.Forms;assembly=ZXing.Net.Mobile.Forms"
             x:Class="QrCode3.ScanPage">
    <ContentPage.Content>
  <Grid>
   <Grid.RowDefinitions>
    <RowDefinition Height="*" />
    <RowDefinition Height="Auto" />
    <RowDefinition Height="*" />
   </Grid.RowDefinitions>

   <BoxView Grid.Row="0" BackgroundColor="Chocolate"/>
    <zxing:ZXingScannerView Grid.Row="1" x:Name="_scanView" 
          OnScanResult="Handle_OnScanResult" IsScanning="true"
                                WidthRequest="200" HeightRequest="200" />
   <BoxView Grid.Row="2" BackgroundColor="Blue" />
  </Grid>
 </ContentPage.Content>
</ContentPage>

  public void Handle_OnScanResult(Result result)
  {
   Device.BeginInvokeOnMainThread(async () =>
   {
    await DisplayAlert("Scanned result", result.Text, "OK");
   });
  }