The CaptureElement XAML control is a cool and easy technique to preview the camera on a device in your application's canvas without having to invoke the CameraCaptureUI dialog.
But... adding more than one doesn't seem to work.
Trying this:
var _MediaCapture = new MediaCapture();
await _MediaCapture.InitializeAsync();
Cap1.Source = _MediaCapture;
Cap2.Source = _MediaCapture;
await _MediaCapture.StartPreviewAsync();
Results in this on the second 'Source' line:
{"A method was called at an unexpected time. (Exception from HRESULT: 0x8000000E)"}
Is there a technique that allows more than one CaptureElement on a single XAML canvas?
Related
I have an Image in a grid where I display some custom content by setting the Image's source to a WritableBitmap and updating the bitmap. What I want to do is to implement a "detach" button that will put my Image on a separate window allowing the user to move it to a different screen, resize it etc. independent of my main app window. If the new window is closed, I would like to bring it back to its original spot. While the Image is on the new window, I want to continuously update it with new content via updating source bitmap (as it would have been before it was detached).
I initially thought I would be able to create a new window and "move" my Image control there by first removing it from its original parent then adding it as a child to a layout in the new window. I used the code below:
CoreApplicationView^ newCoreView = CoreApplication::CreateNewView();
int mainViewId = Windows::UI::ViewManagement::ApplicationView::GetApplicationViewIdForWindow(
CoreApplication::MainView->CoreWindow);
uint indexOfObjectToDetach = -1;
bool found = originalGrid->Children->IndexOf(imageToMove, &indexOfObjectToDetach);
if(found)
{
myGrid->Children->RemoveAt(indexOfObjectToDetach);
}
DispatchedHandler^ dispatchHandler = ref new DispatchedHandler([this, mainViewId]()
{
newView_ = Windows::UI::ViewManagement::ApplicationView::GetForCurrentView();
Windows::UI::Xaml::Controls::StackPanel^ newWindowGrid = ref new Windows::UI::Xaml::Controls::StackPanel();
Window::Current->Content = newWindowGrid;
Window::Current->Activate();
newWindowGrid->Children->Append(imageToMove); // Add to new parent
});
create_task(newCoreView->Dispatcher->RunAsync(Windows::UI::Core::CoreDispatcherPriority::Normal, dispatchHandler)).then([this, mainViewId]()
{
auto a = newView_->Id;
create_task(ApplicationViewSwitcher::TryShowAsStandaloneAsync(a, ViewSizePreference::Default, mainViewId, ViewSizePreference::Default));
});
However in the line where I add the Image to its new parent, I get an Interface was marshalled for a different thread error. Upon more reading, this is due to the fact that each new window is in its own thread and I'm moving an object to another thread.
I am new to UWP and I am not sure how to approach implementing this UI behavior. How do I access/transfer my state in one view to another ?
The problem is indeed the fact that each application view in UWP has its own thread and its own UI dispatcher. When you create a control, it is tied to the UI thread it was created on, hence you cannot place it onto another application view.
The solution is to create the new Image next to the StackPanel within the new view's UI thread. I don't really use C++, but in C# I would implement it as follows:
await newCoreView.Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
{
StackPanel panel = new StackPanel();
Image image = new Image();
panel.Children.Add( panel );
image.Source = ...; //your source
Window.Current.Content = frame;
Window.Current.Activate();
newViewId = ApplicationView.GetForCurrentView().Id;
});
To further clarify - you can safely "transfer" normal data types into other view, the problem is mainly with the UI-tied types like controls, pages, etc.
I am developing an UWP application with a camera feature, I have studied this sets of codes,
https://github.com/Microsoft/Windows-universal-samples/tree/master/Samples/CameraStarterKit
And successfully developed a camera feature on my application. However, in my application, I wish to not store the picture into my local machine as the application is actually like a kiosk system whereby everyone will be using the same machine to take the picture.
What I am planning to do is actually to allow users to send the picture that they have taken to their own email address via the kiosk system. When they have taken a photo, a preview will be shown, and only if the user want to send the picture, then will the picture be "save"
The codes for my take photo function is something like this:
rivate async Task TakePhotoAsync()
{
var stream = new InMemoryRandomAccessStream();
Debug.WriteLine("Taking photo...");
await _mediaCapture.CapturePhotoToStreamAsync(ImageEncodingProperties.CreateJpeg(), stream);
try
{
var file = await _captureFolder.CreateFileAsync("SimplePhoto.jpg", CreationCollisionOption.GenerateUniqueName);
Debug.WriteLine("Photo taken! Saving to " + file.Path);
var photoOrientation = CameraRotationHelper.ConvertSimpleOrientationToPhotoOrientation(_rotationHelper.GetCameraCaptureOrientation());
await ReencodeAndSavePhotoAsync(stream, file, photoOrientation);
Debug.WriteLine("Photo saved!");
}
catch (Exception ex)
{
// File I/O errors are reported as exceptions
Debug.WriteLine("Exception when taking a photo: " + ex.ToString());
}
}
And to get the preview of the picture will be:
private async Task GetPreviewFrameAsSoftwareBitmapAsync()
{
// Get information about the preview
var previewProperties = _mediaCapture.VideoDeviceController.GetMediaStreamProperties(MediaStreamType.VideoPreview) as VideoEncodingProperties;
// Create the video frame to request a SoftwareBitmap preview frame
var videoFrame = new VideoFrame(BitmapPixelFormat.Bgra8, (int)previewProperties.Width, (int)previewProperties.Height);
// Capture the preview frame
using (var currentFrame = await _mediaCapture.GetPreviewFrameAsync(videoFrame))
{
// Collect the resulting frame
SoftwareBitmap previewFrame = currentFrame.SoftwareBitmap;
// Show the frame information
FrameInfoTextBlock.Text = String.Format("{0}x{1} {2}", previewFrame.PixelWidth, previewFrame.PixelHeight, previewFrame.BitmapPixelFormat);
// Create a SoftwareBitmapSource to display the SoftwareBitmap to the user
var sbSource = new SoftwareBitmapSource();
await sbSource.SetBitmapAsync(previewFrame);
// Display it in the Image control
PreviewFrameImage.Source = sbSource;
}
}
There are (at least) two ways:
1) "Better" one:
Create a backend that sends email using SmtpClient
Post your image from UWP to backend using HttpClient
2) "Easier" one: launch Mail app
The downside is that users will be able to edit the message, receiver and things like that.
Also you can try to use SmtpClient directly from UWP client (may be now with .Net Standard 2.0 it would be possible but I guess no one yet tried) or third-party open-source replacement (which might be a bit outdated as it was created for Windows 8) or even try to launch your backend as Windows Service on the client machine.
Instead of creating a Windows built-in camera UI (CameraCaptureUI) or using a custom MediaCapture control and capture picture I want to open any Camera App downloaded in the device to capture an image and get the result.
I have used
string uriToLaunch = "microsoft.windows.camera:";
var uri = new Uri(uriToLaunch);
var success = await Windows.System.Launcher.LaunchUriAsync(uri);
But this just opens the camera app, I need to get the result file back to the app and save it.
Is there a way to do this?
The method you are using:
var success = await Windows.System.Launcher.LaunchUriAsync(uri);
just opens the default camera, nothing more, the result is a boolean with information if the application has been opened successfully, nothing more.
With CameraCaptureUI you don't need to create camera - this seems to be designed for the task like you have described. With lines:
var captureUI = new CameraCaptureUI();
captureUI.PhotoSettings.Format = CameraCaptureUIPhotoFormat.Jpeg;
captureUI.PhotoSettings.CroppedSizeInPixels = new Size(200, 200);
var photo = await captureUI.CaptureFileAsync(CameraCaptureUIMode.Photo);
you just launch the camera app and your app waits for the photo, which you can process further/save.
If you don't want to use it or implement own camera capture, you can think of sharing a picture taken by other app. This is described well at app-to-app communication at MSDN. In this case user will have to click Share button and choose your app as a target. That will invoke OnShareTargetActivated event where you can process the received content.
I am using MediaCapture to capture photos and store them. It works in the emulator. But when running the app on a real phone (Nokia Lumia 530) the captured photos are just black. They have a correct size and the file has a certain byte length, but when displaying the photo it's black. Please note that I do not use Silverlight and am fixed on using MediaCapture. The camera on the phone works when using the default camera app. The App's manifest includes the capabilities "Pictures Library" and "Webcam".
Does someone know what could be wrong?
Here is the test code I use:
using (var mediaCapture = new MediaCapture())
{
await mediaCapture.InitializeAsync();
ImageEncodingProperties imageFormat = ImageEncodingProperties.CreateJpeg();
StorageFile photoFile = await KnownFolders.PicturesLibrary.CreateFileAsync("TestPhoto.jpg", CreationCollisionOption.GenerateUniqueName);
await mediaCapture.CapturePhotoToStorageFileAsync(imageFormat, photoFile);
BitmapImage bitmap = new BitmapImage();
using (var photoStream = await photoFile.OpenReadAsync())
{
bitmap.SetSource(photoStream);
}
}
Edit
I found a solution. The photo is captured correctly if we have a CaptureElement, set it's source to the MediaCapture object, invoke MediaCapture.StartPreviewAsync before taking the photo, take the photo (using CapturePhotoToStorageFileAsync) and finally invoke StopPreviewAsync. It seems that MediaCapture needs an existing (and displayed) preview to be able to capture photos. Strange that this is not documented and using CapturePhotoToStorageFileAsync without a preview does not throw an Exception.
The photo is captured correctly if we have a CaptureElement, set it's source to the MediaCapture object, invoke MediaCapture.StartPreviewAsync before taking the photo, take the photo (using CapturePhotoToStorageFileAsync) and finally invoke StopPreviewAsync. It seems that MediaCapture needs an existing (and displayed) preview to be able to capture photos. Strange that this is not documented and using CapturePhotoToStorageFileAsync without a preview does not throw an Exception.
I am writing a Windows 8 Store App with Live Tiles. Every live tile is an image that needs to be refreshed every x minutes. I am using a Background Task with a time trigger to generate my image and refresh the tile.
Generating my image implies creating a new one and paint my stuff on it but for some reason I am getting an exception when trying to create a new instance of WriteableBitmap:
var newImage = new Windows.UI.Xaml.Media.Imaging.WriteableBitmap(10, 10);
or
var newImage = BitmapFactory.New(10, 10);
throws this exception:
The application called an interface that was marshalled for a
different thread. (Exception from HRESULT: 0x8001010E
(RPC_E_WRONG_THREAD))
I have an impression this is because there is no UI thread in the Background Task but then again, why would the WriteableBitmap require an UI thread?
Any idea how to workaround this? How would I instantiate the WriteableBitmap in my background task?
Turns out this was not possible in Windows 8.
It was made possible in subsequent versions Win 8.1 and then UWP via the XamlBackgroundTask
You can use Dispatcher
Application.Current.Dispatcher.Invoke(
DispatcherPriority.Normal,
new Action(() => createBitmap)
);
UPDATE
Dispatcher.RunAsync
(CoreDispatcherPriority.Normal,
() => new WriteableBitmap(10, 10));
You still can use the following code:
CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(CoreDispatcherPriority.Normal,
() =>{
// Your UI update code goes here!
WriteableBitmap writeableBmp = BitmapFactory.New(imageWidth, imageHeight);
});
But most probably you will get another exception (InvalidOperationException) saying:
A method was called at an unexpected time. WinRT information: Could not create a new view because the main window has not yet been created.