在Xamarin Forms应用程序中使用ZXing Mobile

Question

currently trying to build an app using ZXing Mobile for Xamarin Forms.

The code compiled without issue. But when trying to run on Android device, I got the following error:

An unhandled exception occcured.

The log shows the following:

[0:] Binding: 'DefaultOverlayTopText' property not found on 'ZXing.Net.Mobile.Forms.ZXingDefaultOverlay', target property: 'ZXing.Net.Mobile.Forms.ZXingDefaultOverlay.TopText'
[0:] Binding: 'DefaultOverlayBottomText' property not found on 'ZXing.Net.Mobile.Forms.ZXingDefaultOverlay', target property: 'ZXing.Net.Mobile.Forms.ZXingDefaultOverlay.BottomText'
[0:] Binding: 'DefaultOverlayShowFlashButton' property not found on 'ZXing.Net.Mobile.Forms.ZXingDefaultOverlay', target property: 'ZXing.Net.Mobile.Forms.ZXingDefaultOverlay.ShowFlashButton'
[0:] Binding: 'DefaultOverlayTopText' property not found on 'ZXing.Net.Mobile.Forms.ZXingDefaultOverlay', target property: 'ZXing.Net.Mobile.Forms.ZXingDefaultOverlay.TopText'
[0:] Binding: 'DefaultOverlayBottomText' property not found on 'ZXing.Net.Mobile.Forms.ZXingDefaultOverlay', target property: 'ZXing.Net.Mobile.Forms.ZXingDefaultOverlay.BottomText'
[0:] Binding: 'DefaultOverlayShowFlashButton' property not found on 'ZXing.Net.Mobile.Forms.ZXingDefaultOverlay', target property: 'ZXing.Net.Mobile.Forms.ZXingDefaultOverlay.ShowFlashButton'

This is how i implemented:

scanButton.Clicked += async (sender, args) =>
            {
                var options = new MobileBarcodeScanningOptions
                {
                    AutoRotate = false,
                    UseFrontCameraIfAvailable = false,
                    TryHarder = true
                };
                var scanPage = new ZXingScannerPage(options)
                {
                    DefaultOverlayTopText = "Align the barcode within the frame",
                    DefaultOverlayBottomText = string.Empty,
                    DefaultOverlayShowFlashButton = true
                };
                // Navigate to our scanner page
                await Navigation.PushAsync(scanPage);

                scanPage.OnScanResult += (result) =>
                {
                    // Stop scanning
                    scanPage.IsScanning = false;

                    // Pop the page and show the result
                    Device.BeginInvokeOnMainThread(async () =>
                    {
                        await Navigation.PopAsync();
                        await DisplayAlert("Scanned Barcode", result.Text, "OK");
                    });
                };
            };  

Also added the following in Android's Main activity, right above Xamarin's own Init :

ZXing.Net.Mobile.Forms.Android.Platform.Init();

Any help is appreciated. Thank you.

Answer 1

I tried your code and found the error was more related to the navigation.

You are using

await Navigation.PushAsync (scanPage);

Make sure you are calling this method from a page which contains a NavigationPage if not you will have a crash.

To fix this you can use

await Navigation.PushModalAsync (scanPage);

instead, which doesn't require a NavigationPage and the resulting page displayed will be modal. Using the line above you will need to also change the way you "pop" the view.

await Navigation.PopModalAsync (true);

Note:

These messages you will appear in the logs even when working.

[0:] Binding: 'DefaultOverlayTopText' property not found on 'ZXing.Net.Mobile.Forms.ZXingDefaultOverlay', target property: 'ZXing.Net.Mobile.Forms.ZXingDefaultOverlay.TopText'
[0:] Binding: 'DefaultOverlayBottomText' property not found on 'ZXing.Net.Mobile.Forms.ZXingDefaultOverlay', target property: 'ZXing.Net.Mobile.Forms.ZXingDefaultOverlay.BottomText'
[0:] Binding: 'DefaultOverlayShowFlashButton' property not found on 'ZXing.Net.Mobile.Forms.ZXingDefaultOverlay', target property: 'ZXing.Net.Mobile.Forms.ZXingDefaultOverlay.ShowFlashButton'
[0:] Binding: 'DefaultOverlayTopText' property not found on 'ZXing.Net.Mobile.Forms.ZXingDefaultOverlay', target property: 'ZXing.Net.Mobile.Forms.ZXingDefaultOverlay.TopText'
[0:] Binding: 'DefaultOverlayBottomText' property not found on 'ZXing.Net.Mobile.Forms.ZXingDefaultOverlay', target property: 'ZXing.Net.Mobile.Forms.ZXingDefaultOverlay.BottomText'
[0:] Binding: 'DefaultOverlayShowFlashButton' property not found on 'ZXing.Net.Mobile.Forms.ZXingDefaultOverlay', target property: 'ZXing.Net.Mobile.Forms.ZXingDefaultOverlay.ShowFlashButton'

Hope this helps.-