swift4 扫描框聚焦和拉近镜头

//镜头聚焦if (videoCaptureDevice.isFocusModeSupported(.autoFocus)){                do { try videoInput?.device.lockForConfiguration() } catch{ }                videoInput?.device.focusMode = .autoFocus                videoInput?.device.unlockForConfiguration()   }

//拉近镜头，当调整deviece时，必须要进行加锁 拉近镜头的代码就是  self.videoCaptureDevice.videoZoomFactor = 3（调整成3倍）
          do {                    try self.videoCaptureDevice.lockForConfiguration()                } catch _ {                    Print("ScanerDevice Error: lockForConfiguration.")                    return                }                                self.videoCaptureDevice.videoZoomFactor = 3                videoCaptureDevice.unlockForConfiguration()