Disabling Keyboard Navigation in .NET MAUI to Prevent Random Button Clicks with Barcode Scanner

[LennartKleymann]

Hello everyone,

I'm working on a .NET MAUI application that uses a hardware barcode scanner. After each barcode scan, the scanner sends an Enter key press. However, this causes an issue in the app because random buttons sometimes get focused and clicked after a scan due to keyboard navigation.

I've set up SharpHook to intercept the barcode inputs and check for the timing between keystrokes to distinguish actual scans from manual input. While this approach works for handling the barcode data itself, the problem persists with the automatic Enter key triggering unwanted button clicks.

Here’s what I’m looking for: I’d like to disable the default keyboard navigation so that the Enter key doesn’t activate a button or change focus within my app. Is there a way to prevent keyboard focus from moving around or to disable keyboard navigation entirely in .NET MAUI?

Any guidance on how to achieve this would be greatly appreciated!

I am only using windows as plattform.

Thanks in advance!

[Stedy59]

Most likely you are using the scanner in "keyboard" mode. What is the maker/model of the barcode hardware? You should be able to use the manufacturers sdk or simply modify the scanner to not send a carriage return with the data. Let me know....

[LennartKleymann]

The scanner we are using are cheap and don't have an sdk.

[stephenquan]

If you know that the barcode scanner is sending an Enter key, you can incorporate that in your Barcode detection with the use of an Entry field as follows:

<Entry x:Name="barcodeEntry" Completed="barcodeEntry_Completed" IsEnabled="True" Opacity="0" Unfocused="barcodeEntry_Unfocused" />

The corresponding code-behind will be:

private async void barcodeEntry_Unfocused(object sender, FocusEventArgs e)
{
    Entry entry = (Entry)sender;
    if (IsEnabled)
    {
        await Task.Delay(50);
        entry.Focus();
    }
}

private void barcodeEntry_Completed(object sender, EventArgs e)
{
    Entry entry = (Entry)sender;
    Trace.WriteLine($"Barcode scanned: {entry.Text}");
}

This means, whilst you're expecting barcode input, navigation is neutralized, and the Enter will be used to complete the barcode handler.

I took liberties in hiding the Entry component with Opacity="0" but, whether you need to follow through or adapt this idea is really up to you.

[LennartKleymann]

Thank you for the suggestion!

However, in my application, I use a global hook to handle barcode input, so I don’t rely on a specific Entry being focused for the barcode scanner to work. Instead of managing focus on individual UI components, I’m looking for a way to globally disable keyboard navigation triggered by the Enter key.

The main goal is to prevent Enter key presses from inadvertently interacting with UI elements, such as buttons, across the entire application. This would ensure that the keyboard input from the barcode scanner does not interfere with the app's navigation or trigger unexpected behavior.

If there’s a way to completely disable or override keyboard navigation (specifically for Enter keys) at a global level in .NET MAUI, I’d appreciate further guidance!

Thank you!

[Kalyxt]

If you have detected barcode scan, and you have removed enter from the barcode sequence, what is causing UI to react ?

[LennartKleymann]

In my setup, I’m detecting the barcode sequence in a separate thread outside of MAUI using SharpHook, which works well for identifying scans. However, the Enter key still gets passed to the UI, causing unintended interactions like navigation or button clicks.

To address this, I’ve implemented the following approach:

Microsoft.Maui.Handlers.PageHandler.Mapper.AppendToMapping("MyCustomization", (handler, view) =>  
{  
#if WINDOWS  
    handler.VirtualView.Unfocus();  
    var nativeView = handler?.PlatformView;  
    if (nativeView != null)  
    {  
        nativeView.PreviewKeyDown += PreviewKeyDownEventToPreventKeyboardNavigation;  
    }  
#endif  
});  

private static void PreviewKeyDownEventToPreventKeyboardNavigation(object sender, KeyRoutedEventArgs e)  
{  
    if (e.Key != VirtualKey.Enter)  
        return;  

    var focusedElement = FocusManager.GetFocusedElement((sender as ContentPanel)?.XamlRoot);  
    e.Handled = focusedElement is not TextBox;  
}  

Remaining Challenge:
This solution suppresses Enter key navigation in most cases, but the back button and other UI elements (like buttons) are still triggered. Ideally, I’d like a simpler way to disable Enter key-based navigation globally while preserving its functionality for specific scenarios, such as completing input in a TextBox.

If there’s a better or more efficient way to handle this?