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![Prism Prism](https://us.v-cdn.net/5019960/uploads/FileUpload/74/ae2d24ade22763253b79c93920884f.png)
For those of you who have never used prism before, the Navigation Service is a way of navigation throughout an app from anywhere, namely inside a view model. All you need to do is pass the string of the page you want to navigate to and boom (this page needs to be registered beforehand in the app class). You can embed pages in navigation pages, tabbed pages, master details, assign children and navigate to the bottom of a stack. This functionality is extremely powerful and I recommend anyone who isn’t using an MVVM helper in Xamarin Forms to immediately pickup Prism! Hi Dbnex, I haven’t done anything with external scanners before but I have found a link to a guide that may or may not be helpful.
With an external scanner, you are just changing the camera you are using (from in built to bluetooth) so you would need to connect to the scanner (handling all associated aspects such as permissions, connectivity). Then you could probably use it in a very similar way to how I have outlined in my article. I don’t think ZXing has anything in it to handle external scanners so you might have to get a bit creative! Thanks Alex, One thing I noticed, actually two 1. You are having a bug in code, you are setting isAnalyzing property inside the IsScanning setter. Someone already noticed that I see in your github and created an issue. But more importantly, the OnBarcodeScanned event will not be raised if you scanned the barcode right after app was loaded.
![Can Can](/uploads/1/2/5/5/125543809/994772470.png)
It only gets triggered once you tap on home or recents Android buttons (circle and square), then restore your app using recents (square button on Android screen). If you use Back button (triangle) and then restore your app, scanning will not work again. To get it to work, you have to again tap on either circle or square to restore your app, then if you do scan, it will trigger ONBarcodeScanned event.