volumeControl.m

/*!
 * Do not use in production app.
 */

#if DEBUG
#import <MediaPlayer/MediaPlayer.h>
#endif

- (void)addVolumeControlObserverWithWindow:(UIWindow *)window {
#if DEBUG
    MPVolumeView *volume = [[MPVolumeView alloc] initWithFrame:CGRectZero];
    [window addSubview:volume];

    UISlider *volumeViewSlider;
    for (UIView *view in [volumeViewSlider subviews]){
        if ([[[view class] description] isEqualToString:@"MPVolumeSlider"]) {
            volumeViewSlider = (UISlider *) view;
        }
    }

    // Get volume level of the current output device (speakers, headphones, etc.)
    static float val = 0.0;
    val = [volumeViewSlider value];

    // Register to receive the button-press notifications
    __block id volumeObserver;
    volumeObserver = [[NSNotificationCenter defaultCenter] addObserverForName:@"AVSystemController_SystemVolumeDidChangeNotification" object:nil queue:nil usingBlock:^(NSNotification *note)
    {
        float newVal = [[note.userInfo valueForKey:@"AVSystemController_AudioVolumeNotificationParameter"] floatValue];
        if (newVal >= 1.0) {
            NSLog(@"Up MAX");
        } else if (newVal <= 0.0625) {
            NSLog(@"Down MIN");
        } else if (newVal > val) {
            NSLog(@"Up");
        } else if (newVal < val) {
            NSLog(@"Down");
        } else {
            // should never happen
            NSLog(@"Same");
        }
        val = newVal;
    }];
#endif
}