用代码打开IOS设备的闪光灯

AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];

    if (device.torchMode == AVCaptureTorchModeOff) 
    {
            // Create an AV session
            AVCaptureSession *session = [[AVCaptureSession alloc] init];

            // Create device input and add to current session
            AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device error: nil];
            [session addInput:input];

            // Create video output and add to current session      
            AVCaptureVideoDataOutput *output = [[AVCaptureVideoDataOutput alloc] init];
            [session addOutput:output];

            // Start session configuration
            [session beginConfiguration];
            [device lockForConfiguration:nil];

            // Set torch to on
            [device setTorchMode:AVCaptureTorchModeOn];

            [device unlockForConfiguration];
            [session commitConfiguration];

            // Start the session
            [session startRunning];

            // Keep the session around
            [self setAVSession:session];

            [output release];
    }
    else 
    {
            [AVSession stopRunning];
            [AVSession release], AVSession = nil;
    }
 
</pre>