iOS Detection of Screenshot

Question

The app Snapchat  on the App Store  is an app that lets you share pictures with a self-destruct on them  You can only view the pics for X seconds  If you attempt to take a screenshot while the picture is showing using the home-power key combo  it will tell the sender you tried to take a screenshot   What part of the SDK lets you detect that the user is taking a screenshot  I did not know this was possible

User · Answer

Heres how to do in Swift with closures    func detectScreenShot action     - gt            let mainQueue   NSOperationQueue mainQueue       NSNotificationCenter defaultCenter   addObserverForName UIApplicationUserDidTakeScreenshotNotification  object  nil  queue  mainQueue    notification in            executes after screenshot         action            detectScreenShot      - gt     in     print  User took a screen shot       Swift 4 2  func detectScreenShot action   escaping    - gt            let mainQueue   OperationQueue main     NotificationCenter default addObserver forName  UIApplication userDidTakeScreenshotNotification  object  nil  queue  mainQueue    notification in            executes after screenshot         action             This is included as a standard function in   https   github com goktugyil EZSwiftExtensions  Disclaimer  Its my repo

User · Answer

Looks like there are no direct way to do this to detect if user has tapped on home   power button  As per this  it was possible earlier by using darwin notification  but it doesn t work any more  Since snapchat is already doing it  my guess is that they are checking the iPhone photo album to detect if there is a new picture got added in between this 10 seconds  and in someway they are comparing with the current image displayed  May be some image processing is done for this comparison  Just a thought  probably you can try to expand this to make it work  Check this for more details   Edit   Looks like they might be detecting the UITouch cancel event Screen capture cancels touches  and showing this error message to the user as per this blog  How to detect screenshots on iOS  like SnapChat   In that case you can use     touchesCancelled withEvent  method to sense the UITouch cancellation to detect this  You can remove the image in this delegate method and show an appropriate alert to the user   -  void touchesCancelled  NSSet   touches withEvent  UIEvent   event        super touchesCancelled touches withEvent event        NSLog   Touches cancelled          self imageView removeFromSuperView     and show an alert to the user

User · Answer

Swift 4 Examples  Example  1 using closure  NotificationCenter default addObserver forName   UIApplicationUserDidTakeScreenshot                                          object  nil                                          queue  OperationQueue main    notification in     print    notification  that a screenshot was taken        Example  2 with selector  NotificationCenter default addObserver self                                          selector   selector screenshotTaken                                           name   UIApplicationUserDidTakeScreenshot                                          object  nil    objc func screenshotTaken         print  Screenshot taken

User · Answer

As of iOS 7 the other answers are no longer true  Apple has made it so touchesCancelled withEvent  is no longer called when the user takes a screenshot    This would effectively break Snapchat entirely  so a couple betas in a new solution was added  Now  the solution is as simple as using NSNotificationCenter to add an observer to UIApplicationUserDidTakeScreenshotNotification   Here s an example   Objective C  NSOperationQueue  mainQueue    NSOperationQueue mainQueue     NSNotificationCenter defaultCenter  addObserverForName UIApplicationUserDidTakeScreenshotNotification                                                   object nil                                                    queue mainQueue                                               usingBlock   NSNotification  note                                                        executes after screenshot                                                     Swift  NotificationCenter default addObserver      forName  UIApplication userDidTakeScreenshotNotification      object  nil      queue   main    notification in           executes after screenshot

User · Answer

I found the answer   Taking a screenshot interrupts any touches that are on the screen   This is why snapchat requires holding to see the picture  Reference  http   tumblr jeremyjohnstone com post 38503925370 how-to-detect-screenshots-on-ios-like-snapchat

User · Answer

Swift 4   NotificationCenter default addObserver forName  UIApplication userDidTakeScreenshotNotification  object  nil  queue  OperationQueue main    notification in              you can do anything you want here               by using this observer you can find out when user takes a screenshot  but you can not prevent him

User · Answer

Latest SWIFT 3   func detectScreenShot action   escaping    - gt                let mainQueue   OperationQueue main         NotificationCenter default addObserver forName   UIApplicationUserDidTakeScreenshot  object  nil  queue  mainQueue    notification in                executes after screenshot             action                     In viewDidLoad  call this function  detectScreenShot      - gt     in  print  User took a screen shot       However    NotificationCenter default addObserver self  selector   selector test   name   UIApplicationUserDidTakeScreenshot  object  nil       func test           do stuff here         works totally fine  I don t see any points of mainQueue

[ios] iOS Detection of Screenshot?

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