Getting white screen for scanner dispite of given permissions of camara in android

Issue

Following is the code that I have implemented for scanning qr code in xamarin c#

ZXingScannerView zxing= new ZXingScannerView();
  private void btnScan_Clicked(object sender, EventArgs e)
        {
            try
            {
                zxing = new ZXingScannerView {
                    HorizontalOptions = LayoutOptions.CenterAndExpand,
                    VerticalOptions = LayoutOptions.CenterAndExpand,
                    BackgroundColor = Color.Orange
                };
                NavigationPage.SetHasNavigationBar(this, false);
                zxing.OnScanResult += (result) =>
                {
                    Device.BeginInvokeOnMainThread(async () =>
                    {
                        zxing.IsAnalyzing = false;
                        zxing.IsScanning = false;
                        //MessagingCenter.Send(result, "Scanresult");
                        if (result != null)
                        {
                            await DisplayAlert("Scanned code: ", text, "OK");
                        }
                    });
                };

                var layout = new StackLayout();
                layout.BackgroundColor = Color.Red;
                layout.Children.Add(zxing);

                Content = zxing;

            }
            catch (Exception ex)
            {
                throw ex;
            }
        }

Along with this I have given permission for the camera in androidmanifest.xml. Here is my xml file

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.companyname.xxxxxx" android:installLocation="auto" android:versionCode="1" android:versionName="1.0">
    <uses-sdk android:minSdkVersion="21" android:targetSdkVersion="27" />
    <uses-permission android:name="android.permission.CAMERA" />
    <application android:label="xxxxxx.Android"></application>
    <application android:name="android.support.multidex.MultiDexApplication"></application>
</manifest>

before this I tried implementing the following code:

 private async void btnScan_Clicked(object sender, EventArgs e)
        {
            try
            {
                ZXingScannerPage scanPage = new ZXingScannerPage();
                //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();
                   if (result != null)
                   {                      
                       await DisplayAlert("Scanned code: ", text, "OK");
                   }
               });
               };
               await Navigation.PushAsync(scanPage);
           }
           catch (Exception ex)
           {
               throw ex;
           }
       }

But all the codes are working fine with android 5 but none is working for android 8.1 Can anyone please help to find me if I am missing something?

Solution

But all the codes are working fine with android 5 but none is working for android 8.1

Since Android 6.0, the app must always perform a runtime permission check. Please request the permissions that the app requires in MainAcitivity class.

public override void OnRequestPermissionsResult(int requestCode, string[] permissions, Permission[] grantResults)
{
    global::ZXing.Net.Mobile.Android.PermissionsHandler.OnRequestPermissionsResult(requestCode, permissions, grantResults);
}

Check the tutorial:
https://docs.microsoft.com/en-us/xamarin/android/app-fundamentals/permissions?tabs=windows#requesting-system-permissions

Answered By - Jarvan Zhang