ZXing Xamarin forms white background on IOS

Question

We have a problem with the ZXing Barcodescanner for Xamarin.Forms. The scanner works perfectly on Android, but on IOS I can't see the camera image (preview). The scanner does scan barcodes on IOS if I hold them in front of the camera but the camera preview is just a white background.

I tried playing around with the options but without luck. We are using Prism.Forms for MVVM.

As I mentioned, my code works well on android. Here are some details:

The permissions are properly set on both platforms.
The NuGets ZXing.Net.Mobile and ZXing.Net.Mobile.Forms are added too all three projects (Android, IOS and portable)
We are using .NET Standard 2.0
Xamarin.Forms is version 3.4.0

ScannerView.xaml

<forms:ZXingScannerPage xmlns="http://xamarin.com/schemas/2014/forms"
                    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
                    xmlns:forms="clr-namespace:ZXing.Net.Mobile.Forms;assembly=ZXing.Net.Mobile.Forms"
                    x:Class="App.Portable.View.ScannerView">
<ContentPage.Content>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>
        <forms:ZXingScannerView x:Name="scanner" Grid.Column="0" Grid.Row="0" HorizontalOptions="EndAndExpand" VerticalOptions="FillAndExpand"
                                IsScanning="{Binding IsScanning}"
                                IsAnalyzing="{Binding IsAnalyzing}"
                                Result="{Binding Result, Mode=TwoWay}"
                                ScanResultCommand="{Binding CmdScanResult}"
                                Options="{Binding ScannerOptions}"
        />

        <forms:ZXingDefaultOverlay Grid.Column="0" Grid.Row="0"
                                   TopText="Some title"
                                   ShowFlashButton="False"
                                   BottomText="Some bottom text"
                                   Opacity="0.9"/>
    </Grid>
</ContentPage.Content>

ScannerViewModel.cs

public class ScannerViewModel : ViewModelBase
{
    //Initializing variables

    public ScannerViewModel()
    {
        var options = new MobileBarcodeScanningOptions();
        options.TryHarder = true;
        options.InitialDelayBeforeAnalyzingFrames = 300;
        options.DelayBetweenContinuousScans = 100;
        options.DelayBetweenAnalyzingFrames = 200;
        options.AutoRotate = false;

        ScanningOptions = options;
        Title = "Barcode-Scanner";
        CmdScanResult = new DelegateCommand(OnCmdScanResult);
        IsScanning = true;
        IsAnalyzing = true;
    }

    public MobileBarcodeScanningOptions ScanningOptions
    {
        get => _scanningOptions;

        set => SetProperty(ref _scanningOptions, value);
    }

    public bool IsScanning
    {
        get => _isScanning;

        set => SetProperty(ref _isScanning, value);
    }

    public bool IsAnalyzing
    {
        get => _isAnalyzing;

        set => SetProperty(ref _isAnalyzing, value);
    }

    public Result Result
    {
        get => _result;

        set => SetProperty(ref _result, value);
    }

    public DelegateCommand CmdScanResult { get; }

    private void OnCmdScanResult()
    {
        IsAnalyzing = false;
        IsScanning = false;
        Device.BeginInvokeOnMainThread(
            async () =>
                {
                    IsAnalyzing = false;

                    var parameters = new NavigationParameters();
                    parameters.Add(CodeConstants.BARCODE, Result);
                    await NavigationService.GoBackAsync(parameters);
                });
    }
}

Does anyone see an issue at my code or has some suggestions on how to do it better or at least get it to work?

EDIT: I uploaded a Testproject to my repo to reproduce the error. The Scanner works on iPhone but doesn't show the camera preview: https://gitlab.com/mitti2000/zxingtest

Though it works fine on Android .I don't think the cause is your code .Did you add privacy in info.plist? — Lucas Zhang, Jul 16 '19 at 06:41
@LucasZhang-MSFT Thanks for your comment. I'm not sure what you mean with "privacy". I have this in my info.plist NSCameraUsageDescription Camera permission needed for Barcode-Scanner — mitti2000, Jul 16 '19 at 07:09
Can you share your sample which contains the issue so that I can test it on my side .And don't forget to remove your personal info . — Lucas Zhang, Jul 16 '19 at 07:11
I need some time but I'll create a sample that you can test. — mitti2000, Jul 16 '19 at 09:18
Did you [initialize](https://github.com/Redth/ZXing.Net.Mobile) the plugin in iOS-specific code? In your AppDelegate's FinishedLaunching (..) implementation, call: ZXing.Net.Mobile.Forms.iOS.Platform.Init(); — Leviathan, Jul 16 '19 at 10:17
Yes I did, otherwise, the iOS would't scan. The issue is, that I dont' see the camera image... — mitti2000, Jul 16 '19 at 11:17
Try to re-add the nuget-packages. I use a different Package Source... — mitti2000, Jul 24 '19 at 08:31

score 1 · Accepted Answer · answered Jul 16 '19 at 14:11

1

Cause: You put the ZXingScannerView and ZXingDefaultOverlay in the same cell of grid .Then you set the HorizontalOptions of ZXingScannerView as EndAndExpand .

Solution:

HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand"

answered Jul 16 '19 at 14:11

Lucas Zhang

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ZXing Xamarin forms white background on IOS

1 Answers1