[SG-601] Enhance experience when user denies camera access in Authenticator (#2205)

* [SG-601] Handle camera denied permissions

* [SG-601] Code format

* [SG-601] PR Fixes

* [SG-601] Change resource text to singular

* [SG-601] Remove horizontal and vertical options

* [SG-601] Add start and stop scanner methods

* [SG-601] Remove parameter from ScanPage

* [SG-601] Move initialization to viewmodel

* [SG-601] Fix zxing scanning bug

* [SG-601] Move RunUIThread inside of method

src/App/Pages/Vault/CipherAddEditPage.xaml.cs

@@ -263,12 +263,6 @@ namespace Bit.App.Pages
         {
             if (DoOnce())
             {
-                var cameraPermission = await PermissionManager.CheckAndRequestPermissionAsync(new Permissions.Camera());
-                if (cameraPermission != PermissionStatus.Granted)
-                {
-                    return;
-                }
-
                 var page = new ScanPage(key =>
                 {
                     Device.BeginInvokeOnMainThread(async () =>
@@ -277,6 +271,7 @@ namespace Bit.App.Pages
                         await _vm.UpdateTotpKeyAsync(key);
                     });
                 });
+
                 await Navigation.PushModalAsync(new Xamarin.Forms.NavigationPage(page));
             }
         }

src/App/Pages/Vault/ScanPage.xaml

@@ -34,16 +34,13 @@
             <RowDefinition Height="*" />
             <RowDefinition Height="*" />
         </Grid.RowDefinitions>
-        <zxing:ZXingScannerView
-            x:Name="_zxing"
-            HorizontalOptions="FillAndExpand"
-            VerticalOptions="FillAndExpand"
+        <ContentView 
+            x:Name="_scannerContainer"
             AutomationId="zxingScannerView"
             IsVisible="{Binding ShowScanner}"
             Grid.Column="0"
             Grid.Row="0"
-            Grid.RowSpan="3"
-            OnScanResult="OnScanResult"/>
+            Grid.RowSpan="3"/>
         <StackLayout
             VerticalOptions="Center"
             HorizontalOptions="FillAndExpand"

src/App/Pages/Vault/ScanPage.xaml.cs

@@ -8,8 +8,10 @@ using Bit.Core.Abstractions;
 using Bit.Core.Utilities;
 using SkiaSharp;
 using SkiaSharp.Views.Forms;
+using Xamarin.CommunityToolkit.ObjectModel;
 using Xamarin.Essentials;
 using Xamarin.Forms;
+using ZXing.Net.Mobile.Forms;
 
 namespace Bit.App.Pages
 {
@@ -26,20 +28,15 @@ namespace Bit.App.Pages
         private bool _pageIsActive;
         private bool _qrcodeFound;
         private float _scale;
-
+        private ZXingScannerView _zxing;
         private readonly LazyResolve<ILogger> _logger = new LazyResolve<ILogger>("logger");
 
         public ScanPage(Action<string> callback)
         {
-            _callback = callback;
             InitializeComponent();
-            _zxing.Options = new ZXing.Mobile.MobileBarcodeScanningOptions
-            {
-                UseNativeScanning = true,
-                PossibleFormats = new List<ZXing.BarcodeFormat> { ZXing.BarcodeFormat.QR_CODE },
-                AutoRotate = false,
-                TryInverted = true
-            };
+            _callback = callback;
+            ViewModel.InitScannerCommand = new Command(() => InitScanner());
+
             if (Device.RuntimePlatform == Device.Android)
             {
                 ToolbarItems.RemoveAt(0);
@@ -55,6 +52,53 @@ namespace Bit.App.Pages
         protected override void OnAppearing()
         {
             base.OnAppearing();
+            StartScanner();
+        }
+
+        protected override void OnDisappearing()
+        {
+            StopScanner().FireAndForget();
+            base.OnDisappearing();
+        }
+
+        // Fix known bug with DelayBetweenAnalyzingFrames & DelayBetweenContinuousScans: https://github.com/Redth/ZXing.Net.Mobile/issues/721
+        private void InitScanner()
+        {
+            try
+            {
+                if (!ViewModel.HasCameraPermission || !ViewModel.ShowScanner || _zxing != null)
+                {
+                    return;
+                }
+
+                _zxing = new ZXingScannerView();
+                _zxing.Options = new ZXing.Mobile.MobileBarcodeScanningOptions
+                {
+                    UseNativeScanning = true,
+                    PossibleFormats = new List<ZXing.BarcodeFormat> { ZXing.BarcodeFormat.QR_CODE },
+                    AutoRotate = false,
+                    TryInverted = true,
+                    DelayBetweenAnalyzingFrames = 5,
+                    DelayBetweenContinuousScans = 5
+                };
+                _scannerContainer.Content = _zxing;
+                StartScanner();
+            }
+            catch (Exception ex)
+            {
+                _logger.Value.Exception(ex);
+            }
+        }
+
+        private void StartScanner()
+        {
+            if (_zxing == null)
+            {
+                return;
+            }
+
+            _zxing.OnScanResult -= OnScanResult;
+            _zxing.OnScanResult += OnScanResult;
             _zxing.IsScanning = true;
 
             // Fix for Autofocus, now it's done every 2 seconds so that the user does't have to do it
@@ -98,16 +142,21 @@ namespace Bit.App.Pages
             AnimationLoopAsync();
         }
 
-        protected override async void OnDisappearing()
+        private async Task StopScanner()
         {
+            if (_zxing == null)
+            {
+                return;
+            }
+
             _autofocusCts?.Cancel();
             if (_continuousAutofocusTask != null)
             {
                 await _continuousAutofocusTask;
             }
             _zxing.IsScanning = false;
+            _zxing.OnScanResult -= OnScanResult;
             _pageIsActive = false;
-            base.OnDisappearing();
         }
 
         private async void OnScanResult(ZXing.Result result)

src/App/Pages/Vault/ScanPageViewModel.cs

@@ -1,6 +1,14 @@
-using Bit.App.Resources;
+using System;
+using System.Threading.Tasks;
+using System.Windows.Input;
+using Bit.App.Abstractions;
+using Bit.App.Resources;
 using Bit.App.Utilities;
 using Bit.Core.Abstractions;
+using Bit.Core.Services;
+using Bit.Core.Utilities;
+using Xamarin.CommunityToolkit.ObjectModel;
+using Xamarin.Essentials;
 using Xamarin.Forms;
 
 namespace Bit.App.Pages
@@ -9,13 +17,46 @@ namespace Bit.App.Pages
     {
         private bool _showScanner = true;
         private string _totpAuthenticationKey;
+        private IPlatformUtilsService _platformUtilsService;
+        private IDeviceActionService _deviceActionService;
+        private ILogger _logger;
 
         public ScanPageViewModel()
         {
-            ToggleScanModeCommand = new Command(() => ShowScanner = !ShowScanner);
+            ToggleScanModeCommand = new AsyncCommand(ToggleScanMode, onException: HandleException);
+            _platformUtilsService = ServiceContainer.Resolve<IPlatformUtilsService>("platformUtilsService");
+            _deviceActionService = ServiceContainer.Resolve<IDeviceActionService>("deviceActionService");
+            _logger = ServiceContainer.Resolve<ILogger>();
+            InitAsync().FireAndForget();
         }
 
-        public Command ToggleScanModeCommand { get; set; }
+        public async Task InitAsync()
+        {
+            try
+            {
+                await Device.InvokeOnMainThreadAsync(async () =>
+                {
+                    var hasCameraPermission = await PermissionManager.CheckAndRequestPermissionAsync(new Permissions.Camera());
+                    HasCameraPermission = hasCameraPermission == PermissionStatus.Granted;
+                    ShowScanner = hasCameraPermission == PermissionStatus.Granted;
+                });
+
+                if (!HasCameraPermission)
+                {
+                    return;
+                }
+                InitScannerCommand.Execute(null);
+            }
+            catch (System.Exception ex)
+            {
+                HandleException(ex);
+            }
+        }
+
+        public ICommand ToggleScanModeCommand { get; set; }
+        public ICommand InitScannerCommand { get; set; }
+
+        public bool HasCameraPermission { get; set; }
         public string ScanQrPageTitle => ShowScanner ? AppResources.ScanQrTitle : AppResources.AuthenticatorKeyScanner;
         public string CameraInstructionTop => ShowScanner ? AppResources.PointYourCameraAtTheQRCode : AppResources.OnceTheKeyIsSuccessfullyEntered;
         public string TotpAuthenticationKey
@@ -39,6 +80,23 @@ namespace Bit.App.Pages
                 });
         }
 
+        private async Task ToggleScanMode()
+        {
+            var cameraPermission = await PermissionManager.CheckAndRequestPermissionAsync(new Permissions.Camera());
+            HasCameraPermission = cameraPermission == PermissionStatus.Granted;
+            if (!HasCameraPermission)
+            {
+                var openAppSettingsResult = await _platformUtilsService.ShowDialogAsync(AppResources.EnableCamerPermissionToUseTheScanner, title: string.Empty, confirmText: AppResources.Settings, cancelText: AppResources.NoThanks);
+                if (openAppSettingsResult)
+                {
+                    _deviceActionService.OpenAppSettings();
+                }
+                return;
+            }
+            ShowScanner = !ShowScanner;
+            InitScannerCommand.Execute(null);
+        }
+
         public FormattedString ToggleScanModeLabel
         {
             get
@@ -57,5 +115,15 @@ namespace Bit.App.Pages
                 return fs;
             }
         }
+
+        private void HandleException(Exception ex)
+        {
+            Xamarin.Essentials.MainThread.InvokeOnMainThreadAsync(async () =>
+            {
+                await _deviceActionService.HideLoadingAsync();
+                await _platformUtilsService.ShowDialogAsync(AppResources.GenericErrorMessage);
+            }).FireAndForget();
+            _logger.Exception(ex);
+        }
     }
 }

src/App/Resources/AppResources.Designer.cs

@@ -2128,6 +2128,15 @@ namespace Bit.App.Resources {
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized string similar to Enable camera permission to use the scanner.
+        /// </summary>
+        public static string EnableCamerPermissionToUseTheScanner {
+            get {
+                return ResourceManager.GetString("EnableCamerPermissionToUseTheScanner", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   Looks up a localized string similar to Enabled.
         /// </summary>
@@ -3544,7 +3553,7 @@ namespace Bit.App.Resources {
         }
         
         /// <summary>
-        ///   Looks up a localized string similar to Enterprise Single Sign-On.
+        ///   Looks up a localized string similar to Enterprise single sign-on.
         /// </summary>
         public static string LogInSso {
             get {
@@ -3589,7 +3598,7 @@ namespace Bit.App.Resources {
         }
         
         /// <summary>
-        ///   Looks up a localized string similar to Log In with master password.
+        ///   Looks up a localized string similar to Log in with master password.
         /// </summary>
         public static string LogInWithMasterPassword {
             get {

src/App/Resources/AppResources.resx

@@ -2512,4 +2512,7 @@ Do you want to switch to this account?</value>
   <data name="ThisRequestIsNoLongerValid" xml:space="preserve">
     <value>This request is no longer valid</value>
   </data>
+  <data name="EnableCamerPermissionToUseTheScanner" xml:space="preserve">
+    <value>Enable camera permission to use the scanner</value>
+  </data>
 </root>