ios监听静音键和音量键事件

判断是否静音：

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1. - (BOOL)isMuted  
2. {  
3.     CFStringRef route;  
4.     UInt32 routeSize = sizeof(CFStringRef);  
5.   
6.     OSStatus status = AudioSessionGetProperty(kAudioSessionProperty_AudioRoute, &routeSize, &route);  
7.     if (status == kAudioSessionNoError)  
8.     {  
9.         if (route == NULL || !CFStringGetLength(route))  
10.             return TRUE;  
11.     }  
12.   
13.     return FALSE;  
14. }  

监听静音键：

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1. - (BOOL)addMutedListener  
2. {  
3.     OSStatus s = AudioSessionAddPropertyListener(kAudioSessionProperty_AudioRouteChange,  
4.                                                  audioRouteChangeListenerCallback,  
5.                                                  self);  
6.     return s == kAudioSessionNoError;  
7. }  

回调函数：

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1. void audioRouteChangeListenerCallback (void *inUserData,  
2.                                        AudioSessionPropertyID inPropertyID,  
3.                                        UInt32 inPropertyValueSize,  
4.                                        const void *inPropertyValue  
5.                                        )  
6. {  
7.     if (inPropertyID != kAudioSessionProperty_AudioRouteChange) return;  
8.     BOOL muted = [mediaVolume isMuted];  
9.     // add code here  
10. }  

设置和获取音量：

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1. - (float)volume  
2. {  
3.     return [[MPMusicPlayerController applicationMusicPlayer] volume];  
4. }  
5.   
6. - (void)setVolume:(float)newVolume  
7. {  
8.     [[MPMusicPlayerController applicationMusicPlayer] setVolume:newVolume];  
9. }  

监听音量键：

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1. - (BOOL)addHardKeyVolumeListener  
2. {  
3.     OSStatus s = AudioSessionAddPropertyListener(kAudioSessionProperty_CurrentHardwareOutputVolume,  
4.                                                  audioVolumeChangeListenerCallback,  
5.                                                  self);  
6.     return s == kAudioSessionNoError;  
7. }  

音量键回调函数：

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1. void audioVolumeChangeListenerCallback (void *inUserData,  
2.                                         AudioSessionPropertyID inPropertyID,  
3.                                         UInt32 inPropertyValueSize,  
4.                                         const void *inPropertyValue)  
5. {  
6.     if (inPropertyID != kAudioSessionProperty_CurrentHardwareOutputVolume) return;  
7.     Float32 value = *(Float32 *)inPropertyValue;  
8.     MediaVolume *mediaVolume = (MediaVolume *)inUserData;  
9.     // add code here  
10. }  

方法1：
    在applicationDidFinishLaunching函数里添加
     [[NSNotificationCenter defaultCenter]addObserver:self
                                            selector:@selector(volumeChanged:)
                                            name:@"AVSystemController_SystemVolumeDidChangeNotification"
                                            object:nil];

  - (void)volumeChanged:(NSNotification*)notification
{
    float volume=
   [[[notification userInfo]
     objectForKey:@"AVSystemController_AudioVolumeNotificationParameter"]
    floatValue];
    
   DDLogVerbose(@"current volume = %f",volume);   
}

  弊端：当app进入后天后，依然会监听到volume的变化

2. 对 AudioSession 添加volume变化的 listener,可以放在startAudioSession函数里
    //add alistener for Outputvolume
   AudioSessionAddPropertyListener(kAudioSessionProperty_CurrentHardwareOutputVolume,
                                   volumeListenerCallback,
                                   self
                                   );


void volumeListenerCallback (
                            void                     *inClientData,
                            AudioSessionPropertyID   inID,
                            UInt32                   inDataSize,
                            constvoid               *inData
                            ){
    const float*volumePointer = inData;
    float volume= *volumePointer;
   NSLog(@"volumeListenerCallback %f", volume);
}

3. 获取当前的volume
    float volume = 0.0;
    UInt32dataSize = sizeof(float);
    OSStatusstatus = AudioSessionGetProperty(kAudioSessionProperty_CurrentHardwareOutputVolume,
                            &dataSize,
                            &volume);