问题
I was able to capture video frames from the camera using AVCaptureSession according to http://developer.apple.com/iphone/library/qa/qa2010/qa1702.html. However, it seems that AVCaptureScreen captures frames from the camera without showing the camera stream on the screen. I would like to also show camera stream just like in UIImagePicker so that the user knows that the camera is being turned on and sees what the camera is pointed at. Any help or pointer would be appreciated!
回答1:
AVCaptureVideoPreviewLayer is exactly what you're looking for.
The code fragment Apple uses to demonstrate how to use it is:
AVCaptureSession *captureSession = <#Get a capture session#>;
AVCaptureVideoPreviewLayer *previewLayer = [AVCaptureVideoPreviewLayer layerWithSession:captureSession];
UIView *aView = <#The view in which to present the layer#>;
previewLayer.frame = aView.bounds; // Assume you want the preview layer to fill the view.
[aView.layer addSublayer:previewLayer];
来源：https://stackoverflow.com/questions/3384563/show-camera-stream-while-avcapturesessions-running