iOS 设置系统音量和监听系统音量变化

很简单的调用 

首先在工程引入MediaPlayer.framework

#import <MediaPlayer/MediaPlayer.h>

1. 获取系统音量

// 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;

2.监听方法

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

- (void)volumeChanged:(NSNotification *)notification
{
     [notification.userInfo[@"AVSystemController_AudioVolumeNotificationParameter"] floatValue];

}

 3.记得销毁哦

- (void)dealloc
{

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

}