#import <MediaPlayer/MediaPlayer.h>

// 获取系统音量

MPVolumeView *volumeView = [[MPVolumeView alloc] init];

UISlider *volumeViewSlider= nil;

    for (UIView *view in [volumeView subviews]){

        if ([view.class.description isEqualToString:@"MPVolumeSlider"]){

            volumeViewSlider = (UISlider*)view;

            break;

        }

    }

 float systemVolume = volumeViewSlider.value;

  [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(volumeChanged:) name:@"AVSystemController_SystemVolumeDidChangeNotification" object:nil];

- (void)volumeChanged:(NSNotification *)notification

{

     [notification.userInfo[@"AVSystemController_AudioVolumeNotificationParameter"] floatValue];

}

- (void)dealloc

{

    [[NSNotificationCenter defaultCenter] removeObserver:self name:@"AVSystemController_SystemVolumeDidChangeNotification" object:nil];

}