Opening ZXing Failed: System.NullReferenceException

Hi All, I feel this might be a double up but i have not been able to find a solution for the below error. Please let me know if a solution has been found?

I have recently updated VS to 15.6.7 and subsequently updated to Xamrin.Forms 2.5.1.444934 with Zxing.Net.Mobile 2.4.1 using .NETStandard 2.0. Since doing this I now get a null reference error each time I call the script.

Also I have only seen the error on Android (testing iOS tonight)

Here is the error:

***** ERROR ***** BtnScanQR_Clicked - Opening ZXing Failed: System.NullReferenceException: Object reference not set to an instance of an object. at ZXing.Mobile.MobileBarcodeScanner.GetContext (Android.Content.Context context) [0x0001f] in <57b37b10a314448c8d6b2b9155539100>:0 at ZXing.Mobile.MobileBarcodeScanner.Scan (Android.Content.Context context, ZXing.Mobile.MobileBarcodeScanningOptions options) [0x00015] in <57b37b10a314448c8d6b2b9155539100>:0 at ZXing.Mobile.MobileBarcodeScanner.Scan (ZXing.Mobile.MobileBarcodeScanningOptions options) [0x00001] in <57b37b10a314448c8d6b2b9155539100>:0 at ZXing.Mobile.MobileBarcodeScannerBase.Scan () [0x00006] in <5cc6d3dca85f4634ba661b03b5b196fa>:0 at App.MainPage+<BtnScanQR_Clicked>d__2.MoveNext () [0x00023] in C:\Users\Admin\source\repos\App\App\App\MainPage.xaml.cs:67

In my MainActivity.cs I call the following after my Forms.Int: //QR code reader global::ZXing.Net.Mobile.Forms.Android.Platform.Init();

And this is the script with in my click event on the MainPage.cs:

//Open QR scanner for code scanning private async void BtnScanQR_Clicked(object sender, EventArgs e) { try { var scanner = new MobileBarcodeScanner(); var result = await scanner.Scan(); strAccessToken.Text = result.Text.Trim(); } catch (Exception ex) { GlobalScript.DebugMessages("ERROR", "BtnScanQR_Clicked", "Opening ZXing Failed: " + ex); } }

Even rolling back to my original versions of each package I’m now still having the same error.

Any assistance would be appretiated

[suyana]

@knight1219

if you used mvvmcross 6 ?? add this code at MainActivity Xamarin.Forms.Forms.Init(this, bundle);

[Magnabatt]

Hi All,

Sorry for the delay. I have managed to get this working by updating my on click action to the below;

//Open QR scanner for code scanning private async void BtnScanQR_Clicked(object sender, EventArgs e) { try { var options = new MobileBarcodeScanningOptions { AutoRotate = false, UseFrontCameraIfAvailable = false, TryHarder = true };

var overlay = new ZXingDefaultOverlay { TopText = "Please scan QR code", BottomText = "Align the QR code within the frame" };

var QRScanner = new ZXingScannerPage(options,overlay);

await Navigation.PushModalAsync(QRScanner);

QRScanner.OnScanResult += (result) => { // Stop scanning QRScanner.IsScanning = false;

// Pop the page and show the result Device.BeginInvokeOnMainThread(() => { Navigation.PopModalAsync(true); strAccessToken.Text = result.Text.ToUpper().Trim(); //DisplayAlert("Scanned Barcode", result.Text, "OK"); });

};

} catch (Exception ex) { GlobalScript.SeptemberDebugMessages("ERROR", "BtnScanQR_Clicked", "Opening ZXing Failed: " + ex); } }

Hope this works for you. Also if you find any improvements in the above please share with me.

Packages: Xamarin.Forms 2.5.1.52743 ZXing.Net.Mobile.Forms 2.3.2