NSNotificationCenter PasteboardChangedNotification Not Firing

Question

I\'m writing a custom keyboard for iOS and I\'d like to detect when the user copies some text. I\'ve read that you can use the NSNotificationCenter along with

Answer 1

You cannot use NSNotificationCenter since the keyboard extension is a different process.

Cocoa includes two types of notification centers: The NSNotificationCenter class manages notifications within a single process. The NSDistributedNotificationCenter class manages notifications across multiple processes on a single computer.

Try this solution: https://stackoverflow.com/a/28436058/649379 which uses CFNotifications. Don't forget to enable App Groups to get access to the shared container.

More code here: https://github.com/cxa/AppExtensionCommunicator & https://github.com/mutualmobile/MMWormhole

Answer 2

My not a perfect but work enough solution. I already use it in keyboard.

@interface MyPrettyClass : UIViewController

@end

@implementation MyPrettyClass

@property (strong, nonatomic) NSTimer   *pasteboardCheckTimer;
@property (assign, nonatomic) NSUInteger pasteboardchangeCount;

- (void)viewDidAppear:(BOOL)animated{
    [super viewDidAppear:animated];

    _pasteboardchangeCount = [[UIPasteboard generalPasteboard] changeCount];


    //Start monitoring the paste board
    _pasteboardCheckTimer = [NSTimer scheduledTimerWithTimeInterval:1
                                                             target:self
                                                           selector:@selector(monitorBoard:)
                                                           userInfo:nil
                                                            repeats:YES];
}

- (void)viewDidDisappear:(BOOL)animated{
    [super viewDidDisappear:animated];

    [self stopCheckingPasteboard];
}

#pragma mark - Background UIPasteboard periodical check

- (void) stopCheckingPasteboard{

    [_pasteboardCheckTimer invalidate];
    _pasteboardCheckTimer = nil;
}

- (void) monitorBoard:(NSTimer*)timer{

    NSUInteger changeCount = [[UIPasteboard generalPasteboard]; changeCount];
    if (changeCount != _pasteboardchangeCount) { // means pasteboard was changed

        _pasteboardchangeCount = changeCount;
        //Check what is on the paste board
        if ([_pasteboard containsPasteboardTypes:pasteboardTypes()]){

            NSString *newContent = [UIPasteboard generalPasteboard].string;

            _pasteboardContent = newContent;

            [self tryToDoSomethingWithTextContent:newContent];
        }
    }
}

- (void)tryToDoSomethingWithTextContent:(NSString)newContent{
    NSLog(@"Content was changed to: %@",newContent);
}

@end