一、系統(tǒng)音量的監(jiān)聽

    // 創(chuàng)建單例對象并且使其設(shè)置為活躍狀態(tài).
    [[AVAudioSession sharedInstance] setActive:YES error:nil];
    // 需要開啟該功能以便監(jiān)聽系統(tǒng)音量
    [[UIApplication sharedApplication] beginReceivingRemoteControlEvents];
    // 添加監(jiān)聽系統(tǒng)音量變化
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(onVolumeChanged:) name:@"AVSystemController_SystemVolumeDidChangeNotification" object:nil];

回調(diào)方法：

- (void)onVolumeChanged:(NSNotification *)notification {
    if ([[notification.userInfo objectForKey:@"AVSystemController_AudioCategoryNotificationParameter"] isEqualToString:@"Audio/Video"]) {
        if ([[notification.userInfo objectForKey:@"AVSystemController_AudioVolumeChangeReasonNotificationParameter"] isEqualToString:@"ExplicitVolumeChange"]) {
            CGFloat volume = [[notification.userInfo objectForKey:@"AVSystemController_AudioVolumeNotificationParameter"] floatValue];
            NSLog(@"volume: %@", @(volume));
        }
    }
}

二、耳機(jī)的插入與拔出

    // 創(chuàng)建單例對象并且使其設(shè)置為活躍狀態(tài).
    [[AVAudioSession sharedInstance] setActive:YES error:nil];
    // 添加監(jiān)聽耳機(jī)插入與拔出
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(audioRouteChangeListenerCallback:) name:AVAudioSessionRouteChangeNotification object:[AVAudioSession sharedInstance]];

回調(diào)方法：

- (void)audioRouteChangeListenerCallback:(NSNotification *)notification {
    NSDictionary *interuptionDict = notification.userInfo;
    NSInteger routeChangeReason   = [[interuptionDict valueForKey:AVAudioSessionRouteChangeReasonKey] integerValue];
    
    switch (routeChangeReason) {
        case AVAudioSessionRouteChangeReasonNewDeviceAvailable:
            NSLog(@"AVAudioSessionRouteChangeReasonNewDeviceAvailable");
            //插入耳機(jī)
            break;
        case AVAudioSessionRouteChangeReasonOldDeviceUnavailable:
            NSLog(@"AVAudioSessionRouteChangeReasonOldDeviceUnavailable");
            //拔出耳機(jī)
            break;
    }
}