Android - first scan never works, works only after permissions are given.

I’m running into this exact same issue as this on 2.4.1.

Here’s my scanning page

public class BarcodeScanningPage : ContentPage
    {
        ZXingScannerView ZXingView { get; set; }
        ZXingDefaultOverlay Overlay { get; set; }

        public BarcodeScanningPage() : base()
        {
            Title = "Scanning...";

            ZXingView = new ZXingScannerView
            {
                HorizontalOptions = LayoutOptions.FillAndExpand,
                VerticalOptions = LayoutOptions.FillAndExpand,
                AutomationId = "zxingScannerView",
                Options = new ZXing.Mobile.MobileBarcodeScanningOptions()
                {
                    PossibleFormats = new List<ZXing.BarcodeFormat>() {
                        ZXing.BarcodeFormat.CODE_39, ZXing.BarcodeFormat.QR_CODE
                    }
                }
            };
            ZXingView.OnScanResult += (result) => Device.BeginInvokeOnMainThread(async () =>
            {
                // Stop analysis until we navigate away so we don't keep reading barcodes
                ZXingView.IsAnalyzing = false;

                await NavigationHelper.PushAsync(new SearchResultsPage(new ApiModels.SearchItemsParams()
                {
                    Keyword = result.Text,
                    ResultsPerPage = App.AppConfig.SearchResultsPerPage
                }, result.Text, true));

                //await NavigationHelper.PopAsync();
            });

            Overlay = new ZXingDefaultOverlay()
            {
                BottomText = "Scan Barcodes or QR Codes",
                ShowFlashButton = ZXingView.HasTorch,
                AutomationId = "zxingDefaultOverlay",
            };
            Overlay.FlashButtonClicked += (sender, e) =>
            {
                ZXingView.IsTorchOn = !ZXingView.IsTorchOn;
            };
            var grid = new Grid()
            {
                VerticalOptions = LayoutOptions.FillAndExpand,
                HorizontalOptions = LayoutOptions.FillAndExpand,
            };
            grid.Children.Add(ZXingView);
            grid.Children.Add(Overlay);

            // The root page of your application
            Content = grid;
        }

        protected override void OnAppearing()
        {
            base.OnAppearing();

            ZXingView.IsScanning = true;
        }

        protected override void OnDisappearing()
        {
            ZXingView.IsScanning = false;

            base.OnDisappearing();
        }
}

Any ideas how I might get around this? Thanks! Great plugin.

[Axemasta]

Hi guys, this isn’t a fix but instead a work around.

If you use James Montemagno’s permission library to check for permissions before you present your scanner, the android device will scan on first time load.

[zlannin]

I’m not familiar with Forms but Android needed the following code in my Activity. I’m running 2.4.1.

public override void OnRequestPermissionsResult(int requestCode, string[] permissions, [GeneratedEnum] Permission[] grantResults)
{
    base.OnRequestPermissionsResult(requestCode, permissions, grantResults);
    ZXing.Net.Mobile.Android.PermissionsHandler.OnRequestPermissionsResult(requestCode, permissions, grantResults);
}