如何为带有图像捕捉的相机闪光灯计时？

Question

I want to make it so that my flash will time with when I take a picture, but not sure how. I've tried to do a NSTimer and NSSleep and other ways of timing it, but because sometimes the camera takes longer to focus and take the picture, than other times, it doesn't always get the flash exactly right. How would I accomplish this?

Here is how I do the flash...

func toggleFlash() {
    let device = AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeVideo)
    if (device.hasTorch) {
        device.lockForConfiguration(nil)
        if (device.torchMode == AVCaptureTorchMode.On) {
            device.torchMode = AVCaptureTorchMode.Off
        } else {
            device.setTorchModeOnWithLevel(1.0, error: nil)
        }
        device.unlockForConfiguration()
    }
}

And here is how I take the picture...

func didPressTakePhoto(){

    if let videoConnection = stillImageOutput?.connectionWithMediaType(AVMediaTypeVideo){
        videoConnection.videoOrientation = AVCaptureVideoOrientation.Portrait
        stillImageOutput?.captureStillImageAsynchronouslyFromConnection(videoConnection, completionHandler: {
            (sampleBuffer, error) in

            if sampleBuffer != nil {

                var imageData = AVCaptureStillImageOutput.jpegStillImageNSDataRepresentation(sampleBuffer)
                var dataProvider  = CGDataProviderCreateWithCFData(imageData)
                var cgImageRef = CGImageCreateWithJPEGDataProvider(dataProvider, nil, true, kCGRenderingIntentDefault)

                var image:UIImage!

                if self.camera == true {
                    image = UIImage(CGImage: cgImageRef, scale: 1.0, orientation: UIImageOrientation.Right)

                } else {
                    image = UIImage(CGImage: cgImageRef, scale: 1.0, orientation: UIImageOrientation.LeftMirrored)

                }

                self.tempImageView.image = image
                self.tempImageView.hidden = false

            }


        })
    }


}

Answer 1

In toggleFlash , you need to set

device.flashMode = .On

You're setting the torchMode .

Correcting this should make the flash go off at the right time during captureStillImageAsynchronouslyFromConnection .