Make my Cocoa app respond to the keyboard play/pause key?

Question

Is there a way to make my app respond to the play/pause button on Mac?

EDIT:

Using the suggested code,I get this console message:

Could not connect the action buttonPressed: to target of class NSApplication

Why would that be?

Answer 1

Here's a great article on the subject: http://www.rogueamoeba.com/utm/2007/09/29/

Answer 2

I accomplished this in my own application by subclassing NSApplication (and setting the app's principal class to this subclass). It catches seek and play/pause keys and translates them to specific actions in my app delegate.

Relevant lines:

#import <IOKit/hidsystem/ev_keymap.h>

- (void)sendEvent:(NSEvent *)event
{
    // Catch media key events
    if ([event type] == NSSystemDefined && [event subtype] == 8)
    {
        int keyCode = (([event data1] & 0xFFFF0000) >> 16);
        int keyFlags = ([event data1] & 0x0000FFFF);
        int keyState = (((keyFlags & 0xFF00) >> 8)) == 0xA;

        // Process the media key event and return
        [self mediaKeyEvent:keyCode state:keyState];
        return;
    }

    // Continue on to super
    [super sendEvent:event];
}

- (void)mediaKeyEvent:(int)key state:(BOOL)state
{
    switch (key)
    {
        // Play pressed
        case NX_KEYTYPE_PLAY:
            if (state == NO)
                [(TSAppController *)[self delegate] togglePlayPause:self];
            break;

        // Rewind
        case NX_KEYTYPE_FAST:
            if (state == YES)
                [(TSAppController *)[self delegate] seekForward:self];
            break;

        // Previous
        case NX_KEYTYPE_REWIND:
            if (state == YES)
                [(TSAppController *)[self delegate] seekBack:self];
            break;
    }
}