If you are looking for a free Xamarin component for Barcode Scanner, ZXing.Net.Mobile is what you are looking for.
Get it from: https://components.xamarin.com/view/zxing.net.mobile
I was having 1 little problem when try using ZXing.Net.Mobile barcode scanner in my code. I got the following error:
Error 1 cannot find symbol symbol : class OnActionExpandListener location: class android.support.v4.view.MenuItemCompat android.support.v4.view.MenuItemCompat.OnActionExpandListener D:\Projects\Hybrid Dev\AnacleMobile\AnacleMobile.Droid\obj\Debug\android\src\mono\android\support\v4\view\MenuItemCompat_OnActionExpandListenerImplementor.java 8 41 AnacleMobile.Droid
It turns out the problem was because ZXing.Net.Mobile requires you to reference get and add Xamarin.Android.Support.V4 into reference. And coincidentally, I have added Mono.Android.Support.V4 into reference as well and apparently, you can’t have both Mono.Android.Support.V4 and Xamarin.Android.Support.V4 as in reference. So in this case I just remove Mono.Android.Support.V4 from reference and it compiled fine.
Solution Source: URL.