help with qr codes

Question

help with qr codes

Eduardo Gomez 4,136

I have this VMnamespace Scan2Cart.ViewModels;

public partial class HomePageViewModel(IPageService pageService, IDataProvider dataProvider) : BaseViewModel(pageService) {
    [ObservableProperty]
    public partial bool ShouldDetect { get; set; } = true;
    [ObservableProperty]
    public partial bool _IsProductInfoVisible { get; set; } = false;
    [ObservableProperty]
    public partial Product Product { get; set; }
    [ObservableProperty]
    public partial bool PopUpDetectedOpen { get; set; }
    public ObservableCollection<Product> Products { get; set; } = [];
    [RelayCommand]
    private async Task BarcodesDetected(IEnumerable<BarcodeResult> results) {
        var val = results.FirstOrDefault()?.Value;
        if (string.IsNullOrEmpty(val))
            return;
        var product = await dataProvider.GetProductByIdAsync(val);
        Product = product;
        ShouldDetect = false;
        PopUpDetectedOpen = true;
    }
    [RelayCommand]
    void Yes() {
        if (!Products.Any(x => x.Id == Product.Id)) {
            Products.Add(Product);
            PopUpDetectedOpen = false;
        }
        PopUpDetectedOpen = false;
    }
    [RelayCommand]
    void No() {
        PopUpDetectedOpen = false;
    }
    [RelayCommand]
    void Opening() {
        _IsProductInfoVisible = true;
    }
    [RelayCommand]
    void Closing() {
        _IsProductInfoVisible = false;
        PopUpDetectedOpen = true;
        ShouldDetect = true;
    }
}

and this xaml


    <Grid RowDefinitions="*,Auto">
        <zxing:CameraBarcodeReaderView
            x:Name="CameraView"
            BarcodesDetected="CameraView_BarcodesDetected"
            IsDetecting="{x:Binding ShouldDetect}" />
        <Label
            Margin="10"
            FontAttributes="Bold"
            FontSize="40"
            HorizontalTextAlignment="End"
            Text="121$"
            TextColor="White" />
        <Grid Grid.Row="1">
            <badge:SfBadgeView
                BadgeText="{x:Binding Products.Count}"
                HorizontalOptions="Start"
                VerticalOptions="Center">
                <badge:SfBadgeView.Content>
                    <Label
                        FontFamily="la"
                        FontSize="50"
                        Text="{x:Static fi:IconFont.ShoppingCart}"
                        VerticalTextAlignment="Center" />
                </badge:SfBadgeView.Content>
                <badge:SfBadgeView.BadgeSettings>
                    <badge:BadgeSettings
                        Background="CornflowerBlue"
                        BadgeAlignment="End"
                        Position="TopRight" />
                </badge:SfBadgeView.BadgeSettings>
            </badge:SfBadgeView>
            <Button
                Margin="5"
                CornerRadius="16"
                HeightRequest="25"
                HorizontalOptions="End"
                Text="Pay"
                VerticalOptions="Center"
                WidthRequest="200" />
        </Grid>
        <pop:ProductPage x:Name="ProductPopupControl" IsOpen="{x:Binding PopUpDetectedOpen}" />
    </Grid>

The problem

the scanner scans the first time, but the second time doesn't open anything.

qr to test

IMG20251209223045-min

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Answer accepted by question author

4 additional answers

Your answer

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Answer 1

Hi @Eduardo Gomez ,

Thanks for your feedback. I have looked into it again and I think I have found the root cause.

The main issue was that camera detection wasn’t being re-enabled after the popup closed. In your original code, the Yes(), No(), and Closing() handlers didn’t consistently set ShouldDetect = true, and the Closing() handler was accidentally reopening the popup by setting PopUpDetectedOpen = true. This caused the scanner to remain paused and made it seem like it wasn’t scanning again.

Here’s the fixed full HomePageViewModel.cs code:

namespace Scan2Cart.ViewModels;

public partial class HomePageViewModel(IPageService pageService, IDataProvider dataProvider) : BaseViewModel(pageService) {
    [ObservableProperty]
    public partial bool ShouldDetect { get; set; } = true;
    [ObservableProperty]
    public partial bool _IsProductInfoVisible { get; set; } = false;
    [ObservableProperty]
    public partial Product Product { get; set; }
    [ObservableProperty]
    public partial bool PopUpDetectedOpen { get; set; }
    public ObservableCollection<Product> Products { get; set; } = new ObservableCollection<Product>();

    [RelayCommand]
    private async Task BarcodesDetected(IEnumerable<BarcodeResult> results) {
        var val = results.FirstOrDefault()?.Value;
        if (string.IsNullOrEmpty(val))
            return;
        var product = await dataProvider.GetProductByIdAsync(val);
        Product = product;
        ShouldDetect = false;
        PopUpDetectedOpen = true;
    }

    [RelayCommand]
    void Yes() {
        if (!Products.Any(x => x.Id == Product.Id)) {
            Products.Add(Product);
        }
        // Close popup and resume detection
        PopUpDetectedOpen = false;
        ShouldDetect = true;
    }

    [RelayCommand]
    void No() {
        // Close popup and resume detection
        PopUpDetectedOpen = false;
        ShouldDetect = true;
    }

    [RelayCommand]
    void Opening() {
        _IsProductInfoVisible = true;
    }

    [RelayCommand]
    void Closing() {
        // Ensure popup is closed and camera detection resumes
        _IsProductInfoVisible = false;
        PopUpDetectedOpen = false;
        ShouldDetect = true;
    }
}

Hope this helps! If my answer was helpful - kindly follow the instructions here so others with the same problem can benefit as well.

Answer 2

Jack Dang (WICLOUD CORPORATION) 5,795 Microsoft External Staff Moderator

Hi @Eduardo Gomez ,

Thanks for reaching out.

The behavior you’re seeing happens because the popup is controlled by a boolean flag, and that flag remains true after the first scan. When the scanner detects a second barcode, the value doesn’t actually change (true → true), so the UI has nothing new to react to and the popup won’t reopen.

Additionally, the barcode scanner fires continuously while detecting, which means that if you try to instantly toggle the popup state (false → true) during detection, it will cause flickering.

A reliable way to handle this scenario is to pause barcode detection when the popup is open, and then re-enable detection only after the user closes the popup. This prevents repeated triggers and ensures the popup displays consistently.

Here’s a clean example based on your original ViewModel structure:

[RelayCommand]
private async Task BarcodesDetected(IEnumerable<BarcodeResult> results)
{
    if (PopUpDetectedOpen)
        return; // Ignore new scans while popup is visible

    var val = results.FirstOrDefault()?.Value;
    if (string.IsNullOrEmpty(val))
        return;

    CameraView.IsDetecting = false; // Pause detection

    Product = await dataProvider.GetProductByIdAsync(val);
    PopUpDetectedOpen = true; // Open product popup
}

[RelayCommand]
void Yes()
{
    if (!Products.Any(x => x.Id == Product.Id))
        Products.Add(Product);
    ClosePopup();
}

[RelayCommand]
void No()
{
    ClosePopup();
}

void ClosePopup()
{
    PopUpDetectedOpen = false;    // Close popup
    CameraView.IsDetecting = true; // Resume detection
}

Depending on how your project is structured, your ViewModel might not have direct access to the CameraBarcodeReaderView. If you’re using IPageService, you may already have a way to reference it. But if your ViewModel cannot access UI elements directly, you can safely move the detection toggling to the code-behind instead.

For example, in your page’s code-behind:

private void CameraView_BarcodesDetected(object sender, BarcodeEventArgs e)
{
    if (ViewModel.PopUpDetectedOpen)
        return;

    CameraView.IsDetecting = false;
    ViewModel.BarcodesDetectedCommand.Execute(e.Results);
}

And when the popup closes, you can re-enable detection:

CameraView.IsDetecting = true;

This approach still achieves the same effect, while keeping UI-specific logic in the code-behind and application logic in the ViewModel.

Hope this helps! If my answer was helpful - kindly follow the instructions here so others with the same problem can benefit as well.

Eduardo Gomez 4,136 Reputation points

2025-12-10T23:13:28.0833333+00:00

I did what you recommend me.

I updated the code

So, when the pop-up closes, I enabled the detecting and when I detect I disable the detect
Eduardo Gomez 4,136 Reputation points

2025-12-10T23:26:29.3233333+00:00

It doesn't scan again

github link in private message
Susana Cabrera 0 Reputation points

2025-12-11T02:51:31.4+00:00

CameraView.IsDetecting = true;
Susana Cabrera 0 Reputation points

2025-12-11T02:59:13.7566667+00:00

Hello to everyone else is the right time to make sure it wasn't a good day for my account and can't support me to access my financial please sir ma'am can't accept my request thank you so and have a great day to all of one
Jack Dang (WICLOUD CORPORATION) 5,795 Reputation points Microsoft External Staff Moderator

2025-12-11T10:14:44.28+00:00
Hi @Eduardo Gomez ,

Thanks for your feedback.

After doing some research, I think a missing thing is a small delay when re-enabling detection after closing the popup. You can simply update your ClosePopup() method like this:

void ClosePopup() { PopUpDetectedOpen = false; // Delay briefly to ensure the scanner restarts correctly Task.Delay(200).ContinueWith(_ => { MainThread.BeginInvokeOnMainThread(() => { CameraView.IsDetecting = true; }); }); }

Give it a try and feel free to let me know the result!
Eduardo Gomez 4,136 Reputation points

2025-12-11T11:31:08.6033333+00:00

No I tried it does no scan again

And to make sure it was not the qr, I tried the Bing scanner, and it scan it. I also fount that is hard to read, do you think is thezxing library
Jack Dang (WICLOUD CORPORATION) 5,795 Reputation points Microsoft External Staff Moderator

2025-12-12T03:59:13.8766667+00:00

Hi @Eduardo Gomez ,

Thanks for your feedback.

Your observation makes sense - it could be related to the ZXing library. ZXing.Net.Maui is widely used in MAUI apps, but it’s not an official Microsoft component, and it does have some known limitations with certain QR codes, focus conditions, and continuous detection. So your suspicion is reasonable.

If the issue continues even after fixing the detection flow, the next step is to check whether ZXing is simply struggling with that specific QR code. A good way to confirm this is to test using the native platform APIs (Google ML Kit on Android or Apple Vision on iOS). These are official OS-level technologies and tend to provide more reliable barcode detection. They require a bit more setup, but they’re helpful for isolating whether the decoding issue is coming from ZXing or something else.

Answer 3

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