The code belove works only the first time

The code below doesn't work correctly, it works only on first appearance of the page, after the first scanning if you go back to previous page and return to this page. the scanner doesn't works!!!! try yourself and tell my something about thanks

public partial class PageScanner : ContentPage
{

    public PageScanner()
    {
        InitializeComponent();
    }

    void ZXingScannerView_OnScanResult(ZXing.Result result)
    {
        Device.BeginInvokeOnMainThread(() =>
        {
            scanResultText.Text = result.Text + " (type: " + result.BarcodeFormat.ToString() + ")";
            //Application.Current.MainPage.Navigation.PopAsync();

        });
    }

    protected override void OnAppearing()
    {
        base.OnAppearing();
        fotoCamera.IsScanning = true;
        fotoCamera.IsVisible = true;
    }

Based on the provided code, it seems that you are using the ZXing library for barcode scanning in your Xamarin.Forms application. The issue you described, where the scanner stops working after navigating back and forth, could be related to the lifecycle of the page and the scanner view.

Here are a few suggestions to help troubleshoot and potentially fix the issue:

1. Remove the IsScanning property assignment in the OnAppearing method: The IsScanning property is already set to "True" in the XAML declaration of the ZXingScannerView. Assigning it again in the OnAppearing method may cause unexpected behavior. Try removing the line `fotoCamera.IsScanning = true;` from the OnAppearing method.

2. Handle the OnDisappearing event: Add an event handler for the OnDisappearing event in your PageScanner class. In this event handler, set `fotoCamera.IsScanning = false;` and `fotoCamera.IsVisible = false;` to stop the scanner and hide the camera view when the page is no longer visible. This ensures that the scanner is properly stopped and resources are released.

protected override void OnDisappearing()
{
    base.OnDisappearing();
    fotoCamera.IsScanning = false;
    fotoCamera.IsVisible = false;
}

3. Check for any other potential conflicts: Ensure that there are no other conflicting operations or event handlers that may interfere with the scanner functionality. Review your code and any other components that interact with the scanner view to identify any potential issues.

4. Debug and log messages: Use logging or debug messages to check if the OnScanResult event is being triggered correctly after navigating back to the page. Verify that the result obtained from the barcode scanner is correct and being displayed in the scanResultText label.

By following these suggestions and thoroughly reviewing your code, you should be able to identify and address the issue with the scanner not working correctly after navigating back and forth.

1 Reply

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Rajkiran Swain3y ago
Based on the provided code, it seems that you are using the ZXing library for barcode scanning in your Xamarin.Forms application. The issue you described, where the scanner stops working after navigating back and forth, could be related to the lifecycle of the page and the scanner view.

Here are a few suggestions to help troubleshoot and potentially fix the issue:

1. Remove the IsScanning property assignment in the OnAppearing method: The IsScanning property is already set to "True" in the XAML declaration of the ZXingScannerView. Assigning it again in the OnAppearing method may cause unexpected behavior. Try removing the line `fotoCamera.IsScanning = true;` from the OnAppearing method.

2. Handle the OnDisappearing event: Add an event handler for the OnDisappearing event in your PageScanner class. In this event handler, set `fotoCamera.IsScanning = false;` and `fotoCamera.IsVisible = false;` to stop the scanner and hide the camera view when the page is no longer visible. This ensures that the scanner is properly stopped and resources are released.
```
protected override void OnDisappearing()
{
    base.OnDisappearing();
    fotoCamera.IsScanning = false;
    fotoCamera.IsVisible = false;
}
```
3. Check for any other potential conflicts: Ensure that there are no other conflicting operations or event handlers that may interfere with the scanner functionality. Review your code and any other components that interact with the scanner view to identify any potential issues.

4. Debug and log messages: Use logging or debug messages to check if the OnScanResult event is being triggered correctly after navigating back to the page. Verify that the result obtained from the barcode scanner is correct and being displayed in the scanResultText label.

By following these suggestions and thoroughly reviewing your code, you should be able to identify and address the issue with the scanner not working correctly after navigating back and forth.