Detect permission of camera in iOS - ios

Question

I am developing a very simple video app. I use the official control: UIImagePickerController.
Here is the problem. When presenting the UIImagePickerController for the first time, the iOS will ask for the permission. The user can click yes or no. If the user clicks no, the control is not dismissed. Instead, if the user keeps clicking the start button, the timers go on while the screen is always black, and the user can't stop the timers or go back. The only thing the user can do is to kill the app. The next time the UIImagePickerController is presented, it is still a black screen and the user can't go back if clicking start.
I was wondering if it's a bug. Is there any way we can detect the permission of the camera so that we can decide to show the UIImagePickerController or not?

Answer 1

Check the AVAuthorizationStatus and handle the cases properly.
NSString *mediaType = AVMediaTypeVideo;
AVAuthorizationStatus authStatus = [AVCaptureDevice authorizationStatusForMediaType:mediaType];
if(authStatus == AVAuthorizationStatusAuthorized) {
// do your logic
} else if(authStatus == AVAuthorizationStatusDenied){
// denied
} else if(authStatus == AVAuthorizationStatusRestricted){
// restricted, normally won't happen
} else if(authStatus == AVAuthorizationStatusNotDetermined){
// not determined?!
[AVCaptureDevice requestAccessForMediaType:mediaType completionHandler:^(BOOL granted) {
if(granted){
NSLog(#"Granted access to %#", mediaType);
} else {
NSLog(#"Not granted access to %#", mediaType);
}
}];
} else {
// impossible, unknown authorization status
}

Answer 2

Swift 4 and newer
Make sure to:
import AVFoundation
The code below checks for all possible permission states:
let cameraMediaType = AVMediaType.video
let cameraAuthorizationStatus = AVCaptureDevice.authorizationStatus(for: cameraMediaType)
switch cameraAuthorizationStatus {
case .denied: break
case .authorized: break
case .restricted: break
case .notDetermined:
// Prompting user for the permission to use the camera.
AVCaptureDevice.requestAccess(for: cameraMediaType) { granted in
if granted {
print("Granted access to \(cameraMediaType)")
} else {
print("Denied access to \(cameraMediaType)")
}
}
}
Since iOS 10 you need to specify
NSCameraUsageDescription key in your Info.plist to be able ask for camera access, otherwise your app will crash at runtime. See APIs Requiring Usage Descriptions.
An interesting sidenote from Apple Developer forum:
The system actually kills your app if the user toggles your app's
access to camera in Settings. The same applies to any protected
dataclass in the Settings→Privacy section.

Answer 3

Swift Solution
extension AVCaptureDevice {
enum AuthorizationStatus {
case justDenied
case alreadyDenied
case restricted
case justAuthorized
case alreadyAuthorized
case unknown
}
class func authorizeVideo(completion: ((AuthorizationStatus) -> Void)?) {
AVCaptureDevice.authorize(mediaType: AVMediaType.video, completion: completion)
}
class func authorizeAudio(completion: ((AuthorizationStatus) -> Void)?) {
AVCaptureDevice.authorize(mediaType: AVMediaType.audio, completion: completion)
}
private class func authorize(mediaType: AVMediaType, completion: ((AuthorizationStatus) -> Void)?) {
let status = AVCaptureDevice.authorizationStatus(for: mediaType)
switch status {
case .authorized:
completion?(.alreadyAuthorized)
case .denied:
completion?(.alreadyDenied)
case .restricted:
completion?(.restricted)
case .notDetermined:
AVCaptureDevice.requestAccess(for: mediaType, completionHandler: { (granted) in
DispatchQueue.main.async {
if granted {
completion?(.justAuthorized)
} else {
completion?(.justDenied)
}
}
})
#unknown default:
completion?(.unknown)
}
}
}
And then in order to use it you do
AVCaptureDevice.authorizeVideo(completion: { (status) in
//Your work here
})

Answer 4

As an addition to the answer from #Raptor the following should be mentioned. You may receive the following error starting with iOS 10: This application is modifying the autolayout engine from a background thread after the engine was accessed from the main thread. This can lead to engine corruption and weird crashes.
To fix this, make sure you handle the results from the main thread as follows (Swift 3):
private func showCameraPermissionPopup() {
let cameraMediaType = AVMediaTypeVideo
let cameraAuthorizationStatus = AVCaptureDevice.authorizationStatus(forMediaType: cameraMediaType)
switch cameraAuthorizationStatus {
case .denied:
NSLog("cameraAuthorizationStatus=denied")
break
case .authorized:
NSLog("cameraAuthorizationStatus=authorized")
break
case .restricted:
NSLog("cameraAuthorizationStatus=restricted")
break
case .notDetermined:
NSLog("cameraAuthorizationStatus=notDetermined")
// Prompting user for the permission to use the camera.
AVCaptureDevice.requestAccess(forMediaType: cameraMediaType) { granted in
DispatchQueue.main.sync {
if granted {
// do something
} else {
// do something else
}
}
}
}
}

Answer 5

Specify NSCameraUsageDescription key in Info.plist first.
Then check AVAuthorizationStatus if Authorised then present the UIImagePickerController. It will work.

Answer 6

Swift: Using AVFoundation
Add AVFoundation to Target -> Build Phases -> Link Binary with Libraries.
import AVFoundation on ViewController.
On Info.plist, Add the following:
On View Controller:
#IBAction func cameraButtonClicked(sender: AnyObject) {
let authorizationStatus = AVCaptureDevice.authorizationStatusForMediaType(AVMediaTypeVideo)
print(authorizationStatus.rawValue)
if AVCaptureDevice.authorizationStatusForMediaType(AVMediaTypeVideo) == AVAuthorizationStatus.Authorized{
self.openCameraAfterAccessGrantedByUser()
}
else
{
print("No Access")
dispatch_async(dispatch_get_main_queue()) { [unowned self] in
AVCaptureDevice.requestAccessForMediaType(AVMediaTypeVideo, completionHandler: { (granted :Bool) -> Void in
if granted == true
{
// User granted
self.openCameraAfterAccessGrantedByUser()
}
else
{
// User Rejected
alertToEncourageCameraAccessWhenApplicationStarts()
}
});
}
}
//Open camera
func openCameraAfterAccessGrantedByUser()
{
if(UIImagePickerController .isSourceTypeAvailable(UIImagePickerControllerSourceType.Camera)){
self.cameraAndGalleryPicker!.sourceType = UIImagePickerControllerSourceType.Camera
cameraAndGalleryPicker?.delegate = self
cameraAndGalleryPicker?.allowsEditing = false
cameraAndGalleryPicker!.cameraCaptureMode = .Photo
cameraAndGalleryPicker!.modalPresentationStyle = .FullScreen
presentViewController(self.cameraAndGalleryPicker!, animated: true, completion: nil)
}
else
{
}
}
//Show Camera Unavailable Alert
func alertToEncourageCameraAccessWhenApplicationStarts()
{
//Camera not available - Alert
let cameraUnavailableAlertController = UIAlertController (title: "Camera Unavailable", message: "Please check to see if it is disconnected or in use by another application", preferredStyle: .Alert)
let settingsAction = UIAlertAction(title: "Settings", style: .Destructive) { (_) -> Void in
let settingsUrl = NSURL(string:UIApplicationOpenSettingsURLString)
if let url = settingsUrl {
dispatch_async(dispatch_get_main_queue()) {
UIApplication.sharedApplication().openURL(url)
}
}
}
let cancelAction = UIAlertAction(title: "Okay", style: .Default, handler: nil)
cameraUnavailableAlertController .addAction(settingsAction)
cameraUnavailableAlertController .addAction(cancelAction)
self.window?.rootViewController!.presentViewController(cameraUnavailableAlertController , animated: true, completion: nil)
}