I'm using the following code to launch a secondary window.
static async Task OpenSecondaryWindow(ContentPage contentPage) {
var coreApplicationView = CoreApplication.CreateNewView();
int viewId = 0;
await coreApplicationView.Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () => {
var frame = new Windows.UI.Xaml.Controls.Frame();
frame.Navigate(contentPage);
Window.Current.Content = frame;
Window.Current.Activate();
viewId = ApplicationView.GetForCurrentView().Id;
App.StyleViews();
});
bool viewShown = await ApplicationViewSwitcher.TryShowAsStandaloneAsync(viewId);
}
ContentPage is of the same class that's instantiated and set to MainPage in my Xamarin.Forms.Application.
The problem I'm having is that when sizing the secondary window, the frame sizes, but not the content. What do I need to do to get the content to size as well?
This does the trick.
frame.SizeChanged += delegate (object sender, SizeChangedEventArgs e) {
contentPage.Layout(new Rectangle(0, 0, e.NewSize.Width, e.NewSize.Height));
};
Related
Good Afternoon,
I have a question regarding the performance of the tabbed page and whether there is a more efficient way to load the tabs into the page, without any frame loss or process hang.
Regarding this issue, I have been having a few issues with TabbedPage in Xamarin.Forms. My project currently consists of a Listview with 104 components. When I click on one of the items it opens up a tabbed page consisting of 3 tabed pages. I start the tabbed page using the following code
int Clicked = 0;
public async Task CheckClick(Page data)
{
Clicked += 1;
if (Clicked == 1)
{
await Navigation.PushAsync(data);
List_View.SelectedItem = null;
}
}
public async void OnSelection(object sender, SelectedItemChangedEventArgs e)
{
if (e.SelectedItem == null)
{
return;
}
var Cell = e.SelectedItem as DataSource;
switch (Cell.ID)
{
case 0:
await CheckClick(new Function_One());
break;
}
}
The real problem comes after, whether I pre load the information ahead of time or do what ever, whenever I call Children.Add(data); the whole application hangs for 1 or 2 seconds and than allows the page to load. The code is as follows.
public class Function_One : TabbedPage
{
private async Task Test()
{
//
var data = new NewPageData("", "", "OP.png", "Persian.png", Description, Usage, Storage, Data);
var data2 = new NewMedicalPage(Medical_Info, Translation, startinfo);
var data3 = new NewNotePage("", 0);
data.Icon = "Info.png";
await Task.Delay(100);// Little await to load the page first before hang
Device.BeginInvokeOnMainThread(async () =
{
Children.Add(data);// HERE is the freeze
Children.Add(data2);// these
Children.Add(data3);// 3 (Adding of the Tabs)
});
}
public void UpdateData()
{
Task.Run(async () =
{
try
{
Description.Spans.Add(new Span
{
Text = "Data.... ",
FontSize = 18,
FontFamily = variables.fontFamily
});
Usage.Spans.Add(new Span
{
Text = "MoreData...",
FontSize = 18,
FontFamily = variables.fontFamily
});
Storage.Spans.Add(new Span
{
Text = "LastData...",
FontSize = 18,
FontFamily = variables.fontFamily
});
await Test();
}
catch { }
}).ConfigureAwait(false);
}
public Function_One()
{
UpdateData();
BarBackgroundColor = MainColor;
BarTextColor = Color.WhiteSmoke;
Title = "Page";
}
}
NOTE: (This Project Is Completely An Offline Project, No Internet Needed)
If anyone could explain to me a better method for loading the data while keeping the application flowing and smooth, that would be appreciated. The data does not have to load all at once, just as long as the page opens as soon as its clicked!
I want to open a UIViewController from a content page and this code helps me in doing this
UIWindow Window = new UIWindow(UIScreen.MainScreen.Bounds);
var cvc = new ScanningPage();
var navController = new UINavigationController(cvc);
Window.RootViewController = navController;
Window.MakeKeyAndVisible();
but I also want a Back button on that Controller Page which navigate me back to that content Page.
this.NavigationController.PopViewController(true);
or
this.DismissViewController(true,null);
not working in this case.
I would recommend not creating a new Window and a UINavigationController...
Xamarin.Forms is contained in a single VC in the first Window, so you can obtain that view controller via:
UIApplication.SharedApplication.Windows[0].RootViewController;
So as an example Dependency service that presents and dismisses a VC (either from Forms or the view controller), you can do something like this.
Dependency interface:
public interface IDynamicVC
{
void Show();
void Dismiss();
}
iOS Dependency implementation
public class DynamicVC : IDynamicVC
{
UIViewController vc;
public void Show()
{
if (vc != null) throw new Exception("DynamicVC already showing");
vc = new UIViewController();
var button = new UIButton(new CGRect(100, 100, 200, 200));
button.SetTitle("Back", UIControlState.Normal);
button.BackgroundColor = UIColor.Red;
button.TouchUpInside += (object sender, EventArgs e) =>
{
Dismiss();
};
vc.Add(button);
var rootVC = UIApplication.SharedApplication.Windows[0].RootViewController;
rootVC.PresentViewController(vc, true, () => { });
}
public void Dismiss()
{
vc?.DismissViewController(true, () =>
{
vc.Dispose();
vc = null;
});
}
}
For my studying project, I need to realize an application that has a CameraView or a CameraPage, with a special design. However, I’m not able to figure out how to realize it.
I found a lot of information, to be honest, but they are either obsolete or incomplete, so, I would like to make a point about it, through this thread!
How to implement a Camera?
Well, two solutions can be considered based on what I read.
Camera Page
Let’s say that it’s the first “official” solution. It’s proposed by Xamarin itself, with the Customizing a ContentPage tutorial/documentation. It explains you, through a web page how to implement the camera service with a cross-platform solution.
I then tried the UWP solution:
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="CameraPreviewProject.Sources.Pages.CameraPage">
<ContentPage.Content>
<AbsoluteLayout>
<Button Text="Click me !" AbsoluteLayout.LayoutBounds="0.5, 0.5, 0.1, 0.1" AbsoluteLayout.LayoutFlags="All" />
</AbsoluteLayout>
</ContentPage.Content>
</ContentPage>
Finally, the C# side gives us this:
public partial class CameraPage : ContentPage
{
public CameraPage()
{
InitializeComponent();
}
}
Then, we create a renderer in the UWP side :
using CameraPreviewProject.Sources.Pages;
using CameraPreviewProject.UWP.Sources.PageRenderers;
using System;
using System.Diagnostics;
using System.Linq;
using System.Threading.Tasks;
using Windows.ApplicationModel;
using Windows.Devices.Enumeration;
using Windows.Devices.Sensors;
using Windows.Foundation;
using Windows.Graphics.Display;
using Windows.Graphics.Imaging;
using Windows.Media;
using Windows.Media.Capture;
using Windows.Media.MediaProperties;
using Windows.Storage;
using Windows.Storage.FileProperties;
using Windows.Storage.Streams;
using Windows.System.Display;
using Windows.UI.Core;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Media;
using Xamarin.Forms.Platform.UWP;
[assembly: ExportRenderer(typeof(CameraPage), typeof(CameraPageRenderer))]
namespace CameraPreviewProject.UWP.Sources.PageRenderers
{
public class CameraPageRenderer : PageRenderer
{
private readonly DisplayInformation displayInformation = DisplayInformation.GetForCurrentView();
private readonly SimpleOrientationSensor orientationSensor = SimpleOrientationSensor.GetDefault();
private readonly DisplayRequest displayRequest = new DisplayRequest();
private SimpleOrientation deviceOrientation = SimpleOrientation.NotRotated;
private DisplayOrientations displayOrientation = DisplayOrientations.Portrait;
// Rotation metadata to apply to preview stream (https://msdn.microsoft.com/en-us/library/windows/apps/xaml/hh868174.aspx)
private static readonly Guid RotationKey = new Guid("C380465D-2271-428C-9B83-ECEA3B4A85C1"); // (MF_MT_VIDEO_ROTATION)
private StorageFolder captureFolder = null;
private readonly SystemMediaTransportControls systemMediaControls = SystemMediaTransportControls.GetForCurrentView();
private MediaCapture mediaCapture;
private CaptureElement captureElement;
private bool isInitialized;
private bool isPreviewing;
private bool externalCamera;
private bool mirroringPreview;
private Page page;
private AppBarButton takePhotoButton;
private Application app;
protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.Page> e)
{
base.OnElementChanged(e);
if (e.OldElement != null || Element == null)
{
return;
}
try
{
app = Application.Current;
app.Suspending += OnAppSuspending;
app.Resuming += OnAppResuming;
SetupUserInterface();
SetupCamera();
this.Children.Add(page);
}
catch (Exception ex)
{
Debug.WriteLine(#" ERROR: ", ex.Message);
}
}
protected override Size ArrangeOverride(Size finalSize)
{
page.Arrange(new Rect(0, 0, finalSize.Width, finalSize.Height));
return finalSize;
}
private void SetupUserInterface()
{
takePhotoButton = new AppBarButton
{
VerticalAlignment = VerticalAlignment.Center,
HorizontalAlignment = HorizontalAlignment.Center,
Icon = new SymbolIcon(Symbol.Camera)
};
var commandBar = new CommandBar();
commandBar.PrimaryCommands.Add(takePhotoButton);
captureElement = new CaptureElement();
captureElement.Stretch = Stretch.UniformToFill;
var stackPanel = new StackPanel();
stackPanel.Children.Add(captureElement);
page = new Page();
page.BottomAppBar = commandBar;
page.Content = stackPanel;
page.Unloaded += OnPageUnloaded;
}
private async void SetupCamera()
{
await SetupUIAsync();
await InitializeCameraAsync();
}
#region Event Handlers
private async void OnSystemMediaControlsPropertyChanged(SystemMediaTransportControls sender, SystemMediaTransportControlsPropertyChangedEventArgs args)
{
await Dispatcher.RunAsync(CoreDispatcherPriority.Normal, async () =>
{
// Only handle event if the page is being displayed
if (args.Property == SystemMediaTransportControlsProperty.SoundLevel && page.Frame.CurrentSourcePageType == typeof(MainPage))
{
// Check if the app is being muted. If so, it's being minimized
// Otherwise if it is not initialized, it's being brought into focus
if (sender.SoundLevel == SoundLevel.Muted)
{
await CleanupCameraAsync();
}
else if (!isInitialized)
{
await InitializeCameraAsync();
}
}
});
}
private void OnOrientationSensorOrientationChanged(SimpleOrientationSensor sender, SimpleOrientationSensorOrientationChangedEventArgs args)
{
// Only update orientatino if the device is not parallel to the ground
if (args.Orientation != SimpleOrientation.Faceup && args.Orientation != SimpleOrientation.Facedown)
{
deviceOrientation = args.Orientation;
}
}
private async void OnDisplayInformationOrientationChanged(DisplayInformation sender, object args)
{
displayOrientation = sender.CurrentOrientation;
if (isPreviewing)
{
await SetPreviewRotationAsync();
}
}
private async void OnTakePhotoButtonClicked(object sender, RoutedEventArgs e)
{
await TakePhotoAsync();
}
/*async void OnHardwareCameraButtonPressed(object sender, CameraEventArgs e)
{
await TakePhotoAsync();
}*/
#endregion Event Handlers
#region Media Capture
private async Task InitializeCameraAsync()
{
if (mediaCapture == null)
{
var devices = await DeviceInformation.FindAllAsync(DeviceClass.VideoCapture);
var cameraDevice = devices.FirstOrDefault(c => c.EnclosureLocation != null && c.EnclosureLocation.Panel == Windows.Devices.Enumeration.Panel.Back);
// Get any camera if there isn't one on the back panel
cameraDevice = cameraDevice ?? devices.FirstOrDefault();
if (cameraDevice == null)
{
Debug.WriteLine("No camera found");
return;
}
mediaCapture = new MediaCapture();
try
{
await mediaCapture.InitializeAsync(new MediaCaptureInitializationSettings
{
VideoDeviceId = cameraDevice.Id,
AudioDeviceId = string.Empty,
StreamingCaptureMode = StreamingCaptureMode.Video,
PhotoCaptureSource = PhotoCaptureSource.Photo
});
isInitialized = true;
}
catch (UnauthorizedAccessException)
{
Debug.WriteLine("Camera access denied");
}
catch (Exception ex)
{
Debug.WriteLine("Exception initializing MediaCapture - {0}: {1}", cameraDevice.Id, ex.ToString());
}
if (isInitialized)
{
if (cameraDevice.EnclosureLocation == null || cameraDevice.EnclosureLocation.Panel == Windows.Devices.Enumeration.Panel.Unknown)
{
externalCamera = true;
}
else
{
// Camera is on device
externalCamera = false;
// Mirror preview if camera is on front panel
mirroringPreview = (cameraDevice.EnclosureLocation.Panel == Windows.Devices.Enumeration.Panel.Front);
}
await StartPreviewAsync();
}
}
}
private async Task StartPreviewAsync()
{
// Prevent the device from sleeping while the preview is running
displayRequest.RequestActive();
// Setup preview source in UI and mirror if required
captureElement.Source = mediaCapture;
captureElement.FlowDirection = mirroringPreview ? FlowDirection.RightToLeft : FlowDirection.LeftToRight;
// Start preview
await mediaCapture.StartPreviewAsync();
isPreviewing = true;
if (isPreviewing)
{
await SetPreviewRotationAsync();
}
}
private async Task StopPreviewAsync()
{
isPreviewing = false;
await mediaCapture.StopPreviewAsync();
// Use dispatcher because sometimes this method is called from non-UI threads
await Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
{
// UI cleanup
captureElement.Source = null;
// Allow device screen to sleep now preview is stopped
displayRequest.RequestRelease();
});
}
private async Task SetPreviewRotationAsync()
{
// Only update the orientation if the camera is mounted on the device
if (externalCamera)
{
return;
}
// Derive the preview rotation
int rotation = ConvertDisplayOrientationToDegrees(displayOrientation);
// Invert if mirroring
if (mirroringPreview)
{
rotation = (360 - rotation) % 360;
}
// Add rotation metadata to preview stream
var props = mediaCapture.VideoDeviceController.GetMediaStreamProperties(MediaStreamType.VideoPreview);
props.Properties.Add(RotationKey, rotation);
await mediaCapture.SetEncodingPropertiesAsync(MediaStreamType.VideoPreview, props, null);
}
private async Task TakePhotoAsync()
{
var stream = new InMemoryRandomAccessStream();
await mediaCapture.CapturePhotoToStreamAsync(ImageEncodingProperties.CreateJpeg(), stream);
try
{
var file = await captureFolder.CreateFileAsync("photo.jpg", CreationCollisionOption.GenerateUniqueName);
var orientation = ConvertOrientationToPhotoOrientation(GetCameraOrientation());
await ReencodeAndSavePhotoAsync(stream, file, orientation);
}
catch (Exception ex)
{
Debug.WriteLine("Exception when taking photo: " + ex.ToString());
}
}
private async Task CleanupCameraAsync()
{
if (isInitialized)
{
if (isPreviewing)
{
await StopPreviewAsync();
}
isInitialized = false;
}
if (mediaCapture != null)
{
mediaCapture.Dispose();
mediaCapture = null;
}
}
#endregion Media Capture
#region Helpers
private async Task SetupUIAsync()
{
// Lock page to landscape to prevent the capture element from rotating
DisplayInformation.AutoRotationPreferences = DisplayOrientations.Landscape;
/*// Hide status bar
if (ApiInformation.IsTypePresent("Windows.UI.ViewManagement.StatusBar"))
{
await Windows.UI.ViewManagement.StatusBar.GetForCurrentView().HideAsync();
}*/
displayOrientation = displayInformation.CurrentOrientation;
if (orientationSensor != null)
{
deviceOrientation = orientationSensor.GetCurrentOrientation();
}
RegisterEventHandlers();
var picturesLibrary = await StorageLibrary.GetLibraryAsync(KnownLibraryId.Pictures);
// Fallback to local app storage if no pictures library
captureFolder = picturesLibrary.SaveFolder ?? ApplicationData.Current.LocalFolder;
}
private async Task CleanupUIAsync()
{
UnregisterEventHandlers();
/*if (ApiInformation.IsTypePresent("Windows.UI.ViewManagement.StatusBar"))
{
await Windows.UI.ViewManagement.StatusBar.GetForCurrentView().ShowAsync();
}*/
// Revert orientation preferences
DisplayInformation.AutoRotationPreferences = DisplayOrientations.None;
}
private void RegisterEventHandlers()
{
/*if (ApiInformation.IsTypePresent("Windows.Phone.UI.Input.HardwareButtons"))
{
HardwareButtons.CameraPressed += OnHardwareCameraButtonPressed;
}*/
if (orientationSensor != null)
{
orientationSensor.OrientationChanged += OnOrientationSensorOrientationChanged;
}
displayInformation.OrientationChanged += OnDisplayInformationOrientationChanged;
systemMediaControls.PropertyChanged += OnSystemMediaControlsPropertyChanged;
takePhotoButton.Click += OnTakePhotoButtonClicked;
}
private void UnregisterEventHandlers()
{
/*if (ApiInformation.IsTypePresent("Windows.Phone.UI.Input.HardwareButtons"))
{
HardwareButtons.CameraPressed -= OnHardwareCameraButtonPressed;
}*/
if (orientationSensor != null)
{
orientationSensor.OrientationChanged -= OnOrientationSensorOrientationChanged;
}
displayInformation.OrientationChanged -= OnDisplayInformationOrientationChanged;
systemMediaControls.PropertyChanged -= OnSystemMediaControlsPropertyChanged;
takePhotoButton.Click -= OnTakePhotoButtonClicked;
}
private static async Task ReencodeAndSavePhotoAsync(IRandomAccessStream stream, StorageFile file, PhotoOrientation orientation)
{
using (var inputStream = stream)
{
var decoder = await BitmapDecoder.CreateAsync(inputStream);
using (var outputStream = await file.OpenAsync(FileAccessMode.ReadWrite))
{
var encoder = await BitmapEncoder.CreateForTranscodingAsync(outputStream, decoder);
var properties = new BitmapPropertySet
{
{
"System.Photo.Orientation", new BitmapTypedValue(orientation, Windows.Foundation.PropertyType.UInt16)
}
};
await encoder.BitmapProperties.SetPropertiesAsync(properties);
await encoder.FlushAsync();
}
}
}
#endregion Helpers
#region Rotation
private SimpleOrientation GetCameraOrientation()
{
if (externalCamera)
{
// Cameras that aren't attached to the device do not rotate along with it
return SimpleOrientation.NotRotated;
}
var result = deviceOrientation;
// On portrait-first devices, the camera sensor is mounted at a 90 degree offset to the native orientation
if (displayInformation.NativeOrientation == DisplayOrientations.Portrait)
{
switch (result)
{
case SimpleOrientation.Rotated90DegreesCounterclockwise:
result = SimpleOrientation.NotRotated;
break;
case SimpleOrientation.Rotated180DegreesCounterclockwise:
result = SimpleOrientation.Rotated90DegreesCounterclockwise;
break;
case SimpleOrientation.Rotated270DegreesCounterclockwise:
result = SimpleOrientation.Rotated180DegreesCounterclockwise;
break;
case SimpleOrientation.NotRotated:
result = SimpleOrientation.Rotated270DegreesCounterclockwise;
break;
}
}
// If the preview is mirrored for a front-facing camera, invert the rotation
if (mirroringPreview)
{
// Rotating 0 and 180 ddegrees is the same clockwise and anti-clockwise
switch (result)
{
case SimpleOrientation.Rotated90DegreesCounterclockwise:
return SimpleOrientation.Rotated270DegreesCounterclockwise;
case SimpleOrientation.Rotated270DegreesCounterclockwise:
return SimpleOrientation.Rotated90DegreesCounterclockwise;
}
}
return result;
}
private static int ConvertDeviceOrientationToDegrees(SimpleOrientation orientation)
{
switch (orientation)
{
case SimpleOrientation.Rotated90DegreesCounterclockwise:
return 90;
case SimpleOrientation.Rotated180DegreesCounterclockwise:
return 180;
case SimpleOrientation.Rotated270DegreesCounterclockwise:
return 270;
case SimpleOrientation.NotRotated:
default:
return 0;
}
}
private static int ConvertDisplayOrientationToDegrees(DisplayOrientations orientation)
{
switch (orientation)
{
case DisplayOrientations.Portrait:
return 90;
case DisplayOrientations.LandscapeFlipped:
return 180;
case DisplayOrientations.PortraitFlipped:
return 270;
case DisplayOrientations.Landscape:
default:
return 0;
}
}
private static PhotoOrientation ConvertOrientationToPhotoOrientation(SimpleOrientation orientation)
{
switch (orientation)
{
case SimpleOrientation.Rotated90DegreesCounterclockwise:
return PhotoOrientation.Rotate90;
case SimpleOrientation.Rotated180DegreesCounterclockwise:
return PhotoOrientation.Rotate180;
case SimpleOrientation.Rotated270DegreesCounterclockwise:
return PhotoOrientation.Rotate270;
case SimpleOrientation.NotRotated:
default:
return PhotoOrientation.Normal;
}
}
#endregion Rotation
#region Lifecycle
private async void OnAppSuspending(object sender, SuspendingEventArgs e)
{
var deferral = e.SuspendingOperation.GetDeferral();
await CleanupCameraAsync();
await CleanupUIAsync();
deferral.Complete();
}
private async void OnAppResuming(object sender, object o)
{
await SetupUIAsync();
await InitializeCameraAsync();
}
private async void OnPageUnloaded(object sender, RoutedEventArgs e)
{
await CleanupCameraAsync();
await CleanupUIAsync();
}
#endregion Lifecycle
}
}
This idea is pretty logic, you have a basic page, but which have renderer that preview the camera in the background, I mean, this is the idea I understood, however, it only gives you a white screen that throws an exception… (x86)
Exception initializing MediaCapture - \\?\USB#VID_045E&PID_0779&MI_00#6&2E9BBB25&0&0000#{e5323777-f976-4f5b-9b55-b94699c46e44}\GLOBAL: System.Runtime.InteropServices.COMException (0xC00DABE6): The current capture source does not have an independent photo stream.
The current capture source does not have an independent photo stream.
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.GetResult()
at CameraPreviewProject.UWP.Sources.PageRenderers.CameraPageRenderer.<InitializeCameraAsync>d__25.MoveNext()
Then I click the button of the downside woft menu and get:
Exception thrown: 'System.Runtime.InteropServices.COMException' in System.Private.CoreLib.ni.dll
WinRT information: This object needs to be initialized before the requested operation can be carried out.
I’m a Xamarin Fan, but on that part, I’m not. This link about MediaCapture can be interesting though!
CameraView
To be honest, it’s so way easier to have a control as a button!
<Camera/>
Well, let’s have a look at it! I found a couple of solutions:
Moment MVVM logic - It seems to work only with Android & iOS
Xlabs Camera Unable to try since I can’t start VS2017 from the .sln. Also, I couldn't test the UWP side because it's an MVVM logic..
Xam.Plugin.Media This solution works on UWP !! But run a new activity/instance/page with a native design, so this isn't the solution searched
So, my question is “Does someone could create an element public class Camera() that can be used and declared as a simple xamarin forms button?”
Because, I saw as well 2 others projects about it, one I can’t remember, but the second one is Barcode Scanning but I’m not able to understand or take back the code to implement it as I would like…
It seems so easy and it’s so hard to get, why? Because finally, we’re talking about a view/image that displays a stream from a camera? A camera is just a service where you have methods such as TakePictureAsync() or anything like that? Rotate(), Switch(ViewSide vs), etc etc?
So, I searched about getting a frame view or display the stream of the camera into an image or a view.. I began from those links:
UWP get live webcam video stream by David Pine
UWP stream Webcam over socket to mediaElement I just made some changes
because the subject is a bit different, but.. I couldn't make it work
To be honest, I don’t know what to try now… I’m lost because, at the same time, I tried some Xamarin Forms solution, but also some proper UWP solutions and … nothing…. Maybe my point of view is not good, maybe my idea and just on the side, maybe I should try another approach, I don’t know at all..
I was also thinking about creating a class with some interface that I redefine in each platform renderer, but, still nothing…
Do you have please, any idea or any approach?
Note I have cross-posed this to the Xamarin forums.
I have a problem with RefreshControl... I have this code:
In ViewDidLoad() I call method InitializeRefreshControl();
private void InitializeRefreshControl()
{
if (UIDevice.CurrentDevice.CheckSystemVersion(6, 0))
{
//UIRefreshControl iOS6
ordersCollectionView.RefreshControl = new UIRefreshControl();
ordersCollectionView.RefreshControl.AttributedTitle = new NSAttributedString("Pull To Refresh",
new UIStringAttributes()
{
ForegroundColor = UIColor.Red,
KerningAdjustment = 3
});
ordersCollectionView.RefreshControl.ValueChanged += HandleValueChanged;
}
else
{
// old style refresh button and no PassKit for older iOS
NavigationItem.SetRightBarButtonItem(new UIBarButtonItem(UIBarButtonSystemItem.Refresh), false);
NavigationItem.RightBarButtonItem.Clicked += (sender, e) => { Refresh(); };
}
}
HandleValueChange method and Refresh merhod is here:
private void HandleValueChanged(object sender, EventArgs e)
{
ordersCollectionView.RefreshControl.BeginRefreshing();
ordersCollectionView.RefreshControl.AttributedTitle = new NSAttributedString("Refreshing",
new UIStringAttributes()
{
ForegroundColor = UIColor.Blue,
KerningAdjustment = 5
});
Refresh();
ordersCollectionView.RefreshControl.EndRefreshing();
}
private void Refresh()
{
var viewModel = (OrdersViewModel)DataContext;
viewModel.OnReloadData();
}
My problem is when I pull down collectionVIew so Refresh loading is displayed but is stuck no loading effect and still with text "Pull to refresh". When method Refresh end so for 0,1ms is showing loading effect and text "Refreshing" but not before method Refresh... Someone know how solve this problem? Thanks for answer.
It looks like the issue is related to the Refresh(); method being synchronous. You'll need to make this operation happen in the background so that the UI thread is free to provide the animation for the RefreshControl. For example:
private async void HandleValueChanged(object sender, EventArgs e)
{
ordersCollectionView.RefreshControl.BeginRefreshing();
ordersCollectionView.RefreshControl.AttributedTitle = new NSAttributedString("Refreshing",
new UIStringAttributes()
{
ForegroundColor = UIColor.Blue,
KerningAdjustment = 5
});
// await a Task so that operation is done in the background
await Refresh();
ordersCollectionView.RefreshControl.EndRefreshing();
}
// Marked async and Task returning
private async Task Refresh()
{
var viewModel = (OrdersViewModel)DataContext;
// Need to update this method to be a Task returning, async method.
await viewModel.OnReloadData();
}
The above code refactors what you had to use async/await and Tasks. You may need to refactor some more of your code to make that work, including the OnReloadData() method.
There are lots of resources for getting started with Tasks, async and await. I can start you off with this reference from the Xamarin blog.
UPDATE:
I've tried implementing this in an App.cs method called OpenCameraScanner (you would call this on click of a button on the page from which you want to scan):
App.cs
------------------------------------------------
public static ZXingScannerPage ScanPage;
public static ZXing.Result ScanResult;
public static async void OpenCameraScanner()
{
ScanPage = new ZXingScannerPage(customOverlay: customOverlay);
ScanPage.OnScanResult += (result) =>
{
ScanPage.IsScanning = false;
ScanResult = result;
Device.BeginInvokeOnMainThread(() =>
{
App.CurrentApp.CurrentPage.Navigation.PopModalAsync();
App.CurrentApp.CurrentPage.DisplayAlert("Scanned Barcode", result.Text, "OK");
});
};
var scanPage = new NavigationPage(ScanPage);
await App.CurrentApp.CurrentPage.Navigation.PushModalAsync(ScanPage);
}
However, when this method is called, the screen that opens is blank white, and you can't see the camera view behind it. Not sure why?
I'm using ZXing.Mobile in a Xamarin.Forms project (for iOS right now) for camera scanning functionality on an iPad.
Currently, I have it working great with the following 2 lines:
var scanner = new ZXing.Mobile.MobileBarcodeScanner();
var result = await scanner.Scan();
However, when the camera is open to scan, it takes up the entire iPad screen, which is really big.
Question: Is there a way to adjust the size of the camera overlay? (so that it's not full screen)
I see that the scanner.Scan() method takes an optional options parameter of type ZXing.Mobile.MobileBarcodeScanningOptions - I tried playing around with that, but the only possible relevant option there is a CameraResolutionSelector - but I'm having a really hard time finding any documentation on that.
There is a ZXing sample app that shows how to embed the ZXingScannerView and ZXingDefaultOverlay into a Xamarin.Form's Grid:
https://github.com/Redth/ZXing.Net.Mobile/blob/master/Samples/Forms/Core/CustomScanPage.cs
public CustomScanPage () : base ()
{
zxing = new ZXingScannerView
{
HorizontalOptions = LayoutOptions.FillAndExpand,
VerticalOptions = LayoutOptions.FillAndExpand,
AutomationId = "zxingScannerView",
};
zxing.OnScanResult += (result) =>
Device.BeginInvokeOnMainThread (async () => {
// Stop analysis until we navigate away so we don't keep reading barcodes
zxing.IsAnalyzing = false;
// Show an alert
await DisplayAlert ("Scanned Barcode", result.Text, "OK");
// Navigate away
await Navigation.PopAsync ();
});
overlay = new ZXingDefaultOverlay
{
TopText = "Hold your phone up to the barcode",
BottomText = "Scanning will happen automatically",
ShowFlashButton = zxing.HasTorch,
AutomationId = "zxingDefaultOverlay",
};
overlay.FlashButtonClicked += (sender, e) => {
zxing.IsTorchOn = !zxing.IsTorchOn;
};
var grid = new Grid
{
VerticalOptions = LayoutOptions.FillAndExpand,
HorizontalOptions = LayoutOptions.FillAndExpand,
};
grid.Children.Add(zxing);
grid.Children.Add(overlay);
// The root page of your application
Content = grid;
}