Bug 29885 - CFNotificationCenter Darwin Notifications not working
Summary: CFNotificationCenter Darwin Notifications not working
Alias: None
Product: iOS
Classification: Xamarin
Component: Xamarin.iOS.dll ()
Version: XI 8.10
Hardware: Macintosh Mac OS
: Normal normal
Target Milestone: 8.10.2 (C5SR2)
Assignee: Bugzilla
Depends on:
Reported: 2015-05-08 13:50 UTC by Josh
Modified: 2015-05-20 09:31 UTC (History)
5 users (show)

Is this bug a regression?: ---
Last known good build:

here it is. (13.20 KB, application/zip)
2015-05-08 15:10 UTC, Josh

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Description Josh 2015-05-08 13:50:03 UTC
I am trying to add Darwin Notifications to communicate between my main iOS app and my WatchKitExtension. After having no luck getting notified in the WatchKitExtension when posting from the main app, I tried an even simpler standalone experiment in a separate app that shows that adding observers to the Darwin notification center fail.

In a Single View iOS app I added the following lines into ViewDidLoad which should get fired when the iPhone is locked:

const string notificationName = "com.apple.springboard.lockcomplete";

			var token = CFNotificationCenter.Darwin.AddObserver(
				name: notificationName, 
				objectToObserve: null,
				notificationHandler: (name, userInfo) => {
				// this check should really only be necessary if you reuse this one callback method
				//  for multiple Darwin notification events

				Console.WriteLine("got here");
				suspensionBehavior: CFNotificationSuspensionBehavior.DeliverImmediately);

But the notificationHandler never gets fired. I tried it with a variety of Apple-defined Darwin notifications and never got anything. When hovering over an instance of CFNotificationCenter.Darwin in the debugger, I see that there are always "0 listeners" which probably explains why the handler never gets invoked.

I've also attached zipped up and attached my sample solution.


Comment 1 Josh 2015-05-08 13:51:34 UTC
The comparable code in XCode with Objective C works immediately. Since I don't appear to have the ability to attach additional files, just paste this code into a Single View App's viewController and watch your output window when you lock the iOS Simulator:

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    CFNotificationCenterAddObserver(CFNotificationCenterGetDarwinNotifyCenter(), //center
                                    NULL, // observer
                                    displayStatusChanged, // callback
                                    CFSTR("com.apple.springboard.lockcomplete"), // event name
                                    NULL, // object

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.

static void displayStatusChanged(CFNotificationCenterRef center, void *observer, CFStringRef name, const void *object, CFDictionaryRef userInfo) {
    NSLog(@"event received!");
    // you might try inspecting the `userInfo` dictionary, to see
    //  if it contains any useful info
    if (userInfo != nil) {

Comment 2 Sebastien Pouliot 2015-05-08 15:04:25 UTC
> I've also attached zipped up and attached my sample solution.

There's nothing attached to the bug report. maybe it failed to upload ?
Comment 3 Josh 2015-05-08 15:10:23 UTC
Created attachment 11135 [details]
here it is.

Let me try again.
Comment 4 Sebastien Pouliot 2015-05-08 16:18:19 UTC
Thanks for the test case! Your diagnosis is right (but there's something to fix too).
Comment 5 Sebastien Pouliot 2015-05-19 10:16:05 UTC
Fixed in maccore/master 8e235c06a4e02eabdbda3a20f613918a25bc0450 (last commit of 3)

We're planning on backporting this for 8.10.2 once QA has verified the fix.
Comment 6 Sunil Kumar 2015-05-20 09:31:02 UTC
I have checked this issue with patch build monotouch- .Now this issue is working fine notificationHandler will get fired once we locked the screen. Here is the screencast for the same: http://www.screencast.com/t/S9685t5Z

Hence closing this issue.