zxing qr/barcode scanning using MVVM?

Question

Im new in xamarin, Im trying to make a Button that opens a scanner form that scans qr/barcode that is MVVM method. Im trying to get the result and display it into a label. this is my best guest but it doesn't work, hope someone can help.

view:
<StackLayout>
 <Label Text="{Binding CodigoQr}"/>
 <zxing:ZXingScannerView x:Name="ucZXingScannerView" 
  IsScanning="True" 
  IsAnalyzing="True"
  Result="{Binding CodigoQr}"
  ScanResultCommand="{Binding ScanCommand }" />
 </StackLayout>

ViewModel:
public class BarcodeScanVM : BaseViewModel
    {
        private Result _codigoQr;
        public Result CodigoQr
        {
            get { return _codigoQr; }
            set
            {
                _codigoQr = value;
                OnPropertyChanged();
            }
        }
        public AsyncCommand ScanCommand { get; set; }
        public BarcodeScanVM()
        {
            ScanCommand = new AsyncCommand(OnScanResultCommand);
        }
        async Task OnScanResultCommand()
        {
            var text = CodigoQr;
        }
    }```

Answer 1

You can use the code-behind the view for the actions. And use the VM for other properties

XAML:

 <zxing:ZXingScannerView
        IsAnalyzing="{Binding IsAnalyzing}"
        IsScanning="{Binding IsScanning}"
        OnScanResult="CameraScanner_OnScanResult" />

Code behind:

private void CameraScanner_OnScanResult(ZXing.Result result)
        {   
             ((MyViewModel)BindingContext).OnScanComplete(result.Text);
        }

Answer 2

update: I tried this one, seems like the scanning command works but the program stops afterwards.

ViewMode:
private Result bcScanResult;
    public Result BcScanResult
    {
        get => bcScanResult;
        set
        {

            if (value == bcScanResult)
                return;
            bcScanResult = value;
            OnPropertyChanged();
        }
    }

  public AsyncCommand BcScanCommand { get; }

  public CodeScanVM()
    {
        BcScanCommand = new AsyncCommand(BcScanCommand_Call);
    }

  async Task BcScanCommand_Call()
    {
        await App.Current.MainPage.DisplayAlert("Item", "Code Async 
        Command:" + Result, "OK");
        return;
    }

 View:
 <zxing:ZXingScannerView
            x:Name="ScanView"
            Result="{Binding BcScanResult}"
            ScanResultCommand="{Binding BcScanCommand }"
            IsScanning="True"
            WidthRequest="300"
            HeightRequest="300"/>

Answer 3

Try without using ScannerView. In XAML add a Label (I'm using an Entry) and a Button that opens the scanner:

<Button Text="QR Scan"
        TextColor="White"
        CornerRadius="30"
        Clicked="ButtonScan"/>

<Entry BackgroundColor="White"
       IsTextPredictionEnabled="False"
       TextTransform="Uppercase"
       FontSize="Body"
       TextChanged="Search"
       Placeholder="Search"
       TextColor="Black"
       PlaceholderColor="Black"
       x:Name="lblBarcode"
       Keyboard="Chat">

On the Clicked Event of the Button:

private async void ButtonScan(object sender, EventArgs e)
    {
        PermissionStatus granted = await Permissions.CheckStatusAsync<Permissions.Camera>();
        if (granted != PermissionStatus.Granted)
        {
            _ = await Permissions.RequestAsync<Permissions.Camera>();
        }
        if (granted == PermissionStatus.Granted)
        {
            try
            {
                MobileBarcodeScanner scanner = new MobileBarcodeScanner();
                ZXing.Result result = await scanner.Scan();
                if (result != null && result.Text != "")
                {
                    lblBarcode.Text = result.Text; // <--- This places the result of scanner at Entry/Label
                    scanner.Cancel(); // <--- This closes the scanner
                }
            }
            catch (Exception)
            {
                await DisplayAlert("Problem", "Something went wrong.", "ΟΚ");
            }
        }
        else
        {
            await DisplayAlert("Problem", "No permissions to use camera.", "ΟΚ");
        }
    } 

Answer 4

You can give a look at my sample app on github

xam-barcode-scanner

It works in both platforms and without the need of ZXing library