- (void)getTorch { AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo]; AVCaptureDeviceInput *input = [[AVCaptureDeviceInput alloc]initWithDevice:device error:nil]; AVCaptureVideoDataOutput *output = [[AVCaptureVideoDataOutput alloc] init]; [output setSampleBufferDelegate:self queue:dispatch_get_main_queue()]; self.session = [[AVCaptureSession alloc]init]; [self.session setSessionPreset:AVCaptureSessionPresetHigh]; if ([self.session canAddInput:input]) {  [self.session addInput:input]; } if ([self.session canAddOutput:output]) {  [self.session addOutput:output]; } [self.session startRunning];}- (void)captureOutput:(AVCaptureOutput*)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection*)connection { CFDictionaryRef metadataDict =CMCopyDictionaryOfAttachments(NULL,sampleBuffer,  kCMAttachmentMode_ShouldPropagate); NSDictionary *metadata = [[NSMutableDictionary alloc] initWithDictionary: (__bridgeNSDictionary*)metadataDict]; CFRelease(metadataDict); NSDictionary *exifMetadata = [[metadata objectForKey:(NSString*)kCGImagePropertyExifDictionary] mutableCopy]; float brightnessValue = [[exifMetadata objectForKey:(NSString*)kCGImagePropertyExifBrightnessValue] floatValue]; NSLog(@"%f",brightnessValue); // 根據brightnessValue的值來打開和關閉閃光燈 AVCaptureDevice*device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo]; BOOL result = [device hasTorch];// 判斷設備是否有閃光燈 if((brightnessValue <0) && result) { // 打開閃光燈  [device lockForConfiguration:nil];  [device setTorchMode:AVCaptureTorchModeOn];//開  [device unlockForConfiguration]; }else if((brightnessValue >0) && result) { // 關閉閃光燈  [device lockForConfiguration:nil];    [device setTorchMode:AVCaptureTorchModeOff];//關  [device unlockForConfiguration];  }}