Detect headset button click on iPhone SDK

Question

Is there a way to detect the headset's play/pause button click?

I managed to detect the volume buttons clicks using:

AudioSessionAddPropertyListener( kAudioSessionProperty_CurrentHardwareOutputVolume , audioVolumeChangeListenerCallback, self );

But I can't find an AudioSessionProperty for the center button. What's the way to do that?

Answer 1

Everything that's done from outside your app is considered a "Remote Event". If you double-tap the Home button and press Play/Pause there, it's the equivalent of pressing the play/pause button on the headset (Same for double tapping for next, and triple tapping for previous).

Here's the guide on event handling of remote events for iOS.

Personally, I like subclassing the MainWindow (UIWindow) and overriding the sendEvent: method, so I can manage it more directly:

- (void)sendEvent:(UIEvent *)event
{
    if (event.type == UIEventTypeRemoteControl)
    {
        // Do stuff here
    }
    else
    {
        // Not my problem.
        [super sendEvent:event];
    }
}

Hope that helps, the enum for the event of the central button is UIEventSubtypeRemoteControlTogglePlayPause.

Answer 2

Can's answer was good, but I think it's outdated.

Now you need to subclass UIApplication.

code for main.m

#import <UIKit/UIKit.h>
#import "AppDelegate.h"
#import "MyUIApplication.h"

int main(int argc, char * argv[]) {
  @autoreleasepool {
    return UIApplicationMain(
      argc,
      argv,
      NSStringFromClass([MyUIApplication class]),
      NSStringFromClass([AppDelegate class]));
  }
}

Code for MyUIApplication.m:

@implementation MyUIApplication
- (void)sendEvent:(UIEvent *)event {
  if (event.type == UIEventTypeRemoteControl) {
    // Check event.subtype to see if it's a single click, double click, etc.
  } else {
    // Not my problem.
    [super sendEvent:event];
  }
}
@end

Code for AppDelegate.m:

inside of - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {

call [application beginReceivingRemoteControlEvents];