Generate qr code in xamarin.android

Youssef 46

I have a problem generating qr code. I used a sample from site:
https://www.c-sharpcorner.com/article/generate-barcode-and-qr-code-in-xamarin-android/

But I got a null reference error at this line:
bitmapMatrix = new MultiFormatWriter().encode(message, BarcodeFormat.QR_CODE, size, size);

In my project I have installed the next packages:

Zxing.net.
Xamarin.AndroidX.AppCompat
Xamarin.Essentials
Xamarin.Google.Android.Material

Does anyone have a clue why I am getting a null reference?

Gr. Youssef

Youssef 46 Reputation points

2022-01-17T13:54:16.493+00:00

II have some debug info to show that the null reference come from the writer.encode method.
Viorel 118.4K Reputation points

2022-01-17T14:03:41.103+00:00

When you get the exception, you can also check the Call Stack window to determine certain details.
Youssef 46 Reputation points

2022-01-17T14:16:01.003+00:00

Here I have the stack-trace:

at ZXing.QrCode.QRCodeWriter.encode (System.String contents, ZXing.BarcodeFormat format, System.Int32 width, System.Int32 height, System.Collections.Generic.IDictionary2[TKey,TValue] hints) [0x00120] in <6f4f8ea0232543238f2e06ec9bd0c0fd>:0 at ZXing.MultiFormatWriter.encode (System.String contents, ZXing.BarcodeFormat format, System.Int32 width, System.Int32 height, System.Collections.Generic.IDictionary2[TKey,TValue] hints) [0x0003a] in <6f4f8ea0232543238f2e06ec9bd0c0fd>:0
at ZXing.MultiFormatWriter.encode (System.String contents, ZXing.BarcodeFormat format, System.Int32 width, System.Int32 height) [0x00000] in <6f4f8ea0232543238f2e06ec9bd0c0fd>:0
at Offline.Fragments.PublicKeyShareFragment.GenerateQr () [0x0007c] in C:\Projects\Offline\Offline\Fragments\PublicKeyShareFragment.cs:73
Youssef 46 Reputation points

2022-01-19T09:32:00.403+00:00

The problem with ZXing.net seems to be a bug. I have reported this in github:
https://github.com/micjahn/ZXing.Net/issues/394
Muhammed Suleiman 1 Reputation point

2022-04-17T05:37:55.213+00:00

Hi, please i’d like to ask how i can scan QR code from gallery and also how to generate QR code in Xamarin.android. I have searched all over the net for resources but couldn’t get any in particular. Kindly help
Muhammed Suleiman 1 Reputation point

2022-04-17T05:42:25.087+00:00

Hi, can u pls share this code. I wanna do a similar project

Accepted answer

JarvanZhang 23,961 Reputation points

2022-01-18T09:29:20.78+00:00

Hello yaza,

Welcome to our Microsoft Q&A platform!

The ZXing.Net API may not perform well on Android. Try using ZXing.Net.Mobile nuget instead, which is a mobile-specific. I've tested the function code with this package, it works as expected. The nuget requires the Xamarin.AndroidX.Legacy.Support.V4 dependency, please install the package for your project.

Best Regards,

Jarvan Zhang

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Youssef 46 Reputation points

2022-01-18T10:52:13.77+00:00

Thank you very much. That helped me solve my problem.

JarvanZhang 23,961 Reputation points

2022-01-19T01:07:31.563+00:00

It's my pleasure.
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