ZXing QR Code Generation in Xamarin Forms PCL

问题

I'm trying to generate and display QR code using ZXing package, I tried in following code I was not able to show QR code. It's showing blank image (transparent).

private void OnGenerateQRCodeButton_Clicked(object sender, EventArgs e)
    {

        var writer = new BarcodeWriter
        {
            Format = BarcodeFormat.QR_CODE,
            Options = new EncodingOptions
            {
                Height = (int)imageCompanyLogo.Height,
                Width = (int) imageCompanyLogo.Width,
                Margin = 0,
                PureBarcode = true
            }
        };
        var bitmap = writer.Write("www.helloworld.com");
        imageQRCode.Source = ImageSource.FromStream(() => new MemoryStream(bitmap));
    }

Please suggest any way to do it. Thanks.

回答1:

Debug and see if stream in empty or not.

var stream = (Stream)null;
private void OnGenerateQRCodeButton_Clicked(object sender, EventArgs e)
{

    var writer = new BarcodeWriter
    {
        Format = BarcodeFormat.QR_CODE,
        Options = new EncodingOptions
        {
            Height = (int)imageCompanyLogo.Height,
            Width = (int) imageCompanyLogo.Width,
            Margin = 0,
            PureBarcode = true
        }
    };

    using(var bitmap = barcodeWriter.Write("www.helloworld.com"))
    {

        stream = new MemoryStream();
        bitmap.Save(stream, ImageFormat.Png);
        stream.Seek(0, SeekOrigin.Begin);
    }

    imageQRCode.Source = ImageSource.FromStream(() => new MemoryStream(stream));
 }

回答2:

1. Create interface in PCL(Xamarin) project for Dependency Service.
2. Create a class in Native(Xamarin.Droid) and Inherit from PCL Interface.

3. Implement the method as shown below.

   public Stream ConvertImageStream(string text, int width = 300, int height = 300)
   {
       var barcodeWriter = new ZXing.Mobile.BarcodeWriter
       {
           Format = ZXing.BarcodeFormat.QR_CODE,
           Options = new ZXing.Common.EncodingOptions
           {
               Width = width,
               Height = height,
               Margin = 10
           }
       };
   
       barcodeWriter.Renderer = new ZXing.Mobile.BitmapRenderer();
       var bitmap = barcodeWriter.Write(text);
       var stream = new MemoryStream();
       bitmap.Compress(Bitmap.CompressFormat.Png, 100, stream);  // this is the diff between iOS and Android
       stream.Position = 0;
       return stream;
   }
   

4. call the method from PCL(Xamarin) project using Dependency Service.

5. In xaml.cs

   private void OnGenerateQRCodeButton_Clicked(object sender, EventArgs e)
   {
       string barcodeText = "www.helloworld.com";
       var stream = DependencyService.Get<IBarCodeServices>().ConvertImageStream(barcodeText, (int)imageCompanyLogo.Width,(int) imageCompanyLogo.Height);
       barcodeImage.Source = ImageSource.FromStream(() => stream);
   }
   

来源：https://stackoverflow.com/questions/39249911/zxing-qr-code-generation-in-xamarin-forms-pcl