iOS 监听音量调节事件

做项目需要音量调节的事件来控制其他动作，找了半天，调试了一下，一下代码都可以直接使用。经过测试的。

有两个方法：

方法一：

添加AudioToolbox.framework

Appdelegate.m中，添加头文件#include

在- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary*)launchOptions方法中添加

    AudioSessionInitialize(NULL, NULL, NULL, NULL);

    AudioSessionSetActive(true);

    AudioSessionAddPropertyListener(kAudioSessionProperty_CurrentHardwareOutputVolume ,

                                    volumeListenerCallback,

                                    (__bridge void *)(self)

                                    );

外加回调函数

void volumeListenerCallback (

                             void                      *inClientData,

                             AudioSessionPropertyID    inID,

                             UInt32                    inDataSize,

                             const void                *inData

                             ){

    const float *volumePointer = inData;

    float volume = *volumePointer;

    NSLog(@"volumeListenerCallback %f", volume);

}

搞定。

方法二：较为简单实用

添加MediaPlayer.framework 

　  AVFoundation.framework

在Appdelegate.m中

在- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary*)launchOptions方法中添加

　　NSError *error;
　　[[AVAudioSession sharedInstance] setActive:YES error:&error];//加上这句可以在按音量键的时候不显示音量提示视图

    [[NSNotificationCenter defaultCenter] addObserver:self

                                             selector:@selector(volumeChanged:)

                                             name:@"AVSystemController_SystemVolumeDidChangeNotification"

                                               object:nil];

    [[UIApplication sharedApplication] beginReceivingRemoteControlEvents];//注，ios9上不加这一句会无效，加了这一句后，

    //在移除通知时候加上这句[[UIApplication sharedApplication] endReceivingRemoteControlEvents];

然后添加方法

-(void)volumeChanged:(NSNotification *)noti

{                                   

    float volume =

    [[[noti userInfo]

      objectForKey:@"AVSystemController_AudioVolumeNotificationParameter"]

     floatValue];

    NSLog(@"volumn is %f", volume);

}

　在viewdidload中新增一个音量视图替换掉系统的音量视图

    MPVolumeView *volumeView = [[MPVolumeView alloc] initWithFrame:CGRectMake(0, 0, 200, 20)];

    volumeView.center = CGPointMake(-550,370);//设置中心点，让音量视图不显示在屏幕中

    [volumeView sizeToFit];

    [self.view addSubview:volumeView];

 到此监听音量调节事件就搞定了