ProcessCameraProvider.BindToLifecycle Not Working

Question

I have the following code to bind my camera to a PreviewView:

private void StartPreview()
{
	this.cameraproviderfuture.AddListener(new Runnable(() =>
	{
		//Preview
		this.preview = new Preview.Builder().SetTargetResolution(new Size(1280, 720)).Build();
		this.preview.SetSurfaceProvider(this.pvPreview.SurfaceProvider);

		this.imgcapture = new ImageCapture.Builder().Build();

		CameraSelector camselector = null;
		if (this.cameraprovider.HasCamera(CameraSelector.DefaultBackCamera)) { camselector = CameraSelector.DefaultBackCamera; }
		else if (this.cameraprovider.HasCamera(CameraSelector.DefaultFrontCamera)) { camselector = CameraSelector.DefaultFrontCamera; }
		else { throw new System.Exception("Camera Not Found"); }

		try
		{
			this.cameraprovider.UnbindAll();
			this.cameraprovider.BindToLifecycle(this, camselector, this.preview, this.imgcapture);
		}
		catch (Java.Lang.Exception e) { System.Diagnostics.Debug.WriteLine($"StartPreview: {e.Message}"); }
	}), ContextCompat.GetMainExecutor(this));

	//this.cameraprovider.IsBound(this.preview) is still false at this point
}

However, this does not seem to work (as stated in the comment at the end of the code above), but it also does not give any Exceptions. What is the problem?

Answer 1

Hello,

I tested Xamarin with reference to this official tutorial on Android API level 30, and the results showed that BindToLifecycle works as expected and the IsBound method returns true.

Are you missing permissions or API levels when writing code?

Please refer to the following tutorial and xamarin code sample.

• Getting Started with CameraX.

private void StartCamera()
{
    var cameraProviderFuture = ProcessCameraProvider.GetInstance(this);

   cameraProviderFuture.AddListener(new Runnable(() =>
    {
        // Used to bind the lifecycle of cameras to the lifecycle owner
        var cameraProvider = (ProcessCameraProvider)cameraProviderFuture.Get();

        var preview = new Preview.Builder().Build();
        preview.SetSurfaceProvider(viewFinder.CreateSurfaceProvider());

        this.imageCapture = new ImageCapture.Builder().Build();

        var imageAnalyzer = new ImageAnalysis.Builder().Build();
        imageAnalyzer.SetAnalyzer(cameraExecutor, new LuminosityAnalyzer(luma =>
            Log.Debug(TAG, $"Average luminosity: {luma}")
            ));

       // Select back camera as a default
        CameraSelector cameraSelector = null;
        if (cameraProvider.HasCamera(CameraSelector.DefaultBackCamera) == true)
            cameraSelector = CameraSelector.DefaultBackCamera;
        else if (cameraProvider.HasCamera(CameraSelector.DefaultFrontCamera) == true)
            cameraSelector = CameraSelector.DefaultFrontCamera;
        else
            throw new System.Exception("Camera not found");

       try
        {
            // Unbind use cases before rebinding
            cameraProvider.UnbindAll();

           // Bind use cases to camera
            cameraProvider.BindToLifecycle(this, cameraSelector, preview, imageCapture, imageAnalyzer);
        }
        catch (Exception exc)
        {
            Log.Debug(TAG, "Use case binding failed", exc);
            Toast.MakeText(this, $"Use case binding failed: {exc.Message}", ToastLength.Short).Show();
        }
        var b = cameraProvider.IsBound(preview); // the result will be true.

   }), ContextCompat.GetMainExecutor(this)); 
}

Best Regards,

Alec Liu.

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