iPhone Camera Focussing

问题

I used the below code for focusing the iphone camera. But it is not working. I take this code from the AVCam sample code of Apple. Am I doing anything wrong? Is there any method to detect if the iPhone did focussing?

-(void) focusAtPoint:(CGPoint)point   
{
    AVCaptureDevice *device =  [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];;

    if (device != nil) {            
        if ([device isFocusPointOfInterestSupported] && [device isFocusModeSupported:AVCaptureFocusModeAutoFocus]) {

            NSError *error;

            if ([device lockForConfiguration:&error]) {             
                [device setFocusPointOfInterest:point];             
                [device setFocusMode:AVCaptureFocusModeAutoFocus];              
                [device unlockForConfiguration];                
            } else {                
                NSLog(@"Error in Focus Mode");
            }        

        }
    }
}

回答1:

The point for [AVCaptureDevice setFocusPointOfInterest:] is not the same as the touch point of the view, but a point between 0,0 and 1,1 (see docs). So you have to do:

CGPoint point = [touch locationInView:self.cameraView];
point.x /= self.cameraView.frame.size.width;
point.y /= self.cameraView.frame.size.height;
[self focusAtPoint:point];

来源：https://stackoverflow.com/questions/8065422/iphone-camera-focussing