Locking iOS Camera Exposure Crashes

Question

I have the following code:

-(void) startCameraCapture {
    // start capturing frames
    // Create the AVCapture Session
    session = [[AVCaptureSession alloc] init];

    // create a preview layer to show the output from the camera
    AVCaptureVideoPreviewLayer *previewLayer = [AVCaptureVideoPreviewLayer layerWithSession:session];
    // Specify that the video should be stretched to fill the layer’s bounds.
    previewLayer.videoGravity = AVLayerVideoGravityResize;

    //previewView.frame = CGRectMake(126.0, 164.0, 64.0, 75.0);


    previewLayer.frame = previewView.frame;
    [previewView.layer addSublayer:previewLayer];

    // Get the default camera device
    AVCaptureDevice* camera = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    // get the current settings
    [appDelegate loadSettings];
    [session startRunning];     
}

Is there a way I can lock the exposure of a camera device to only allow the screen to adjust to a certain brightness?

Sorry if I am not asking this right.

Thank you.

EDIT:

I tried adding:

[camera setExposureModeCustomWithDuration:CMTimeMake(1,1) ISO:100 completionHandler:nil];

but that only results in the app crashing at that line.

Answer 1

According to Apple's doc:

An NSGenericException exception is thrown if this method is invoked without first obtaining exclusive access to the receiver using lockForConfiguration:.

So add this line in front:

[camera lockForConfiguration:nil];