Why does live camera capture control with Xamarin Forms on iOS freeze? - xamarin

Question

I downloaded the source for Xamarin Moments from GitHub and now I'm trying to convert the CameraPage renderer from Page to a ContentView
Then I refactored the code to make it a ContentView renderer. Most of the actual setup of the live preview and image capture comes from the Moments app with some refactoring where needed/preferred.
The live preview shows up but when I press the button to take the picture the app freezes without an exception, not even in Xcode's console view.
//this is how it's called:
btnTakePicture.Clicked += (s,e)=> { GetCameraImage().Wait(); };
// this method freezes
public async Task<byte[]> GetCameraImage()
{
byte[] imageBuffer = null;
if (captureDeviceInput != null)
{
var videoConnection = stillImageOutput.ConnectionFromMediaType(AVMediaType.Video);
Console.WriteLine("[HASFIQWRPPOA] This message shows up");
// this is where the app freezes, even though the live preview still moves.
var sampleBuffer = await stillImageOutput.CaptureStillImageTaskAsync(videoConnection);
Console.WriteLine("[CLKJFADSFQXW] THIS DOESN'T SHOW UP");
// var jpegImageAsBytes = AVCaptureStillImageOutput.JpegStillToNSData (sampleBuffer).ToArray ();
var jpegImageAsNsData = AVCaptureStillImageOutput.JpegStillToNSData(sampleBuffer);
Console.WriteLine("[ROIAJDGNQWTG]");
// var image = new UIImage (jpegImageAsNsData);
// var image2 = new UIImage (image.CGImage, image.CurrentScale, UIImageOrientation.UpMirrored);
// var data = image2.AsJPEG ().ToArray ();
imageBuffer = jpegImageAsNsData.ToArray();
Console.WriteLine("[FIOUJGAIDGUQ] Image buffer: "+imageBuffer.Length);
}
if (imageBuffer != null && imageBuffer.Length > 100)
{
using (var ms = new MemoryStream(imageBuffer))
{
var uiimg = UIImage.LoadFromData(NSData.FromStream(ms));
this.Add(new UIImageView(uiimg));
}
}
return imageBuffer;
}
Here is how I set the live preview
// This method runs fine and the camera preview is started as expected
public void SetupLiveCameraStream()
{
try
{
// add a UIView to the renderer
liveCameraStream = new UIView()
{
Frame = new CGRect(0f, 0f, Element.Width, Element.Height),
};
this.Add(liveCameraStream);
// find a camera
var captureDevice = AVCaptureDevice.DefaultDeviceWithMediaType(AVMediaType.Video);
if (captureDevice != null)
{
Console.WriteLine("[ZKSDJGWEHSY] Capture device found"); // not the case on simulator
captureSession = new AVCaptureSession();
videoPreviewLayer = new AVCaptureVideoPreviewLayer(captureSession)
{
Frame = liveCameraStream.Bounds
};
liveCameraStream.Layer.AddSublayer(videoPreviewLayer);
ConfigureCameraForDevice(captureDevice);
captureDeviceInput = AVCaptureDeviceInput.FromDevice(captureDevice);
var dictionary = new NSMutableDictionary();
dictionary[AVVideo.CodecKey] = new NSNumber((int)AVVideoCodec.JPEG);
stillImageOutput = new AVCaptureStillImageOutput()
{
OutputSettings = new NSDictionary()
};
captureSession.AddInput(captureDeviceInput);
captureSession.AddOutput(stillImageOutput);
captureSession.StartRunning();
Console.WriteLine("[OIGAJGUWRJHWY] Camera session started");
}
else
{
Console.WriteLine("[OASDFUJGOR] Could not find a camera device");
}
}
catch (Exception x)
{
Console.WriteLine("[QWKRIFQEAHJF] ERROR:" + x);
}
}

Answer 1

I had this issue, and it turned out I was deadlocking because of a combination of using async/await with Task.Result. At a guess you could be experiencing something similar with your usage of Task.Wait().
The two sections of code:
btnTakePicture.Clicked += await (s,e) => { GetCameraImage().Wait(); };
And:
var sampleBuffer = await stillImageOutput.CaptureStillImageTaskAsync(videoConnection);