AVCaptureVideoPreviewLayer black screen - ios

Question

hello i had a working code with AVCaptureVideoPreviewLayer.. it's a part barcode reader:
let captureDevice = AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeVideo)
do {
let input = try AVCaptureDeviceInput(device: captureDevice) as AVCaptureDeviceInput
session.addInput(input)
print("input done..")
} catch let error as NSError {
print(error)
}
let output = AVCaptureMetadataOutput()
output.setMetadataObjectsDelegate(self, queue: dispatch_get_main_queue())
session.addOutput(output)
output.metadataObjectTypes = output.availableMetadataObjectTypes
previewLayer = AVCaptureVideoPreviewLayer(session: session) as AVCaptureVideoPreviewLayer
previewLayer.frame = self.view.bounds
previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill
self.view.layer.addSublayer(previewLayer)
self.view.bringSubviewToFront(self.highlightView)
session.startRunning()
It was starting and running also, there wasn't any error messeage and i used on my old iPhone too and i could see the picture of the camera. But 2 days ago my iphone's been replaced, i didn't change anything in the code. Now the app starting but i can see only black screen.
Does anybody know what could cause this?
Thank you!

Answer 1

This is the code I used to test this out:
override func viewDidLoad() {
super.viewDidLoad()
var session = AVCaptureSession.new()
session.sessionPreset = AVCaptureSessionPresetMedium
let captureDevice = AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeVideo)
let input = AVCaptureDeviceInput(device: captureDevice, error: nil) as AVCaptureDeviceInput
session.addInput(input)
print("input done..")
var previewLayer = AVCaptureVideoPreviewLayer(session: session) as AVCaptureVideoPreviewLayer
previewLayer.frame = self.view.bounds
previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill
self.view.layer.addSublayer(previewLayer)
session.startRunning()
}
I appears that the problem was that you did not pass in the NSError required by the AVCaptureDeviceInput. Xcode was not sure what the try statement was trying to do as well. I've simply passed in nil into the constructor for now, but you will want to make sure that you handle it. I also removed the part on setting up the output, as that was not relevant to my testing. Feel free to add that back in.
I tested this on my iPhone 4 running iOS 7.1 for reference.

Answer 2

From iOS 8 you need to ask for the permission, you can do something like this
if ([AVCaptureDevice respondsToSelector:#selector(requestAccessForMediaType: completionHandler:)]) {
[AVCaptureDevice requestAccessForMediaType:AVMediaTypeVideo completionHandler:^(BOOL granted) {
if (granted) {
// Got the permission
} else {
// Permission has been denied.
}
}];
} else {
// below ios 6
}
you can execute permission method in swifth
if AVCaptureDevice.respondsToSelector(Selector("requestAccessForMediaType"))
{
AVCaptureDevice.requestAccessForMediaType(AVMediaTypeVideo, completionHandler: { (grandted:Bool) -> Void in
//Check if granted and if its true do camera work else permission denied
})
}
else
{
// Below iOS 6
}