Facebook SDK login never calls back my application on iOS 9

For Swift this was working for me (add it in AppDelegate.swift):

@available(iOS 9.0, *)
func application(application: UIApplication,openURL url: NSURL, options: [String: AnyObject]) -> Bool {
return FBSDKApplicationDelegate.sharedInstance().application(application, 
     openURL: url, 
     sourceApplication: options[UIApplicationOpenURLOptionsSourceApplicationKey] as! String,
     annotation: options [UIApplicationOpenURLOptionsAnnotationKey])
}

and

@available(iOS, introduced=8.0, deprecated=9.0)
func application(application: UIApplication,openURL url: NSURL, sourceApplication: String?, annotation: AnyObject) -> Bool {  
return FBSDKApplicationDelegate.sharedInstance().application(application,
     openURL: url,
     sourceApplication: sourceApplication!,
     annotation: annotation)
}

In each case remember to add import FBSDKCoreKit with the other import statements.

Its basically what Google SignIn uses. If its still not working you need to set the delegates and your info.plist like it is specified in the FaceBook Docs. I hope this helps!

For Swift 3 & Facebook SDK 4.16.0:

Add the following code to AppDelegate.swift

func application(_ application: UIApplication, open url: URL, sourceApplication: String?, annotation: Any) -> Bool {
    return FBSDKApplicationDelegate.sharedInstance().application(application, open: url, sourceApplication: sourceApplication, annotation: annotation)
}

Turns out that on iOS 9 when UIApplicationDelegate's application:openURL:options: is implemented, application:openURL:sourceApplication:annotation: will not get called.

So what I had to do is call FBSDKApplicationDelegate's application:openURL:sourceApplication:annotation: from UIApplicationDelegate's application:openURL:options:

- (BOOL)application:(UIApplication *)app openURL:(NSURL *)url options:(NSDictionary<NSString*, id> *)options {
    return [[FBSDKApplicationDelegate sharedInstance] application:app
                                                      openURL:url
                                            sourceApplication:options[UIApplicationOpenURLOptionsSourceApplicationKey]
                                                   annotation:options[UIApplicationOpenURLOptionsAnnotationKey]];
}