作者  bmwmengwei

原帖地址  http://www.cocoachina.com/bbs/read.php?tid-14440.html

App程序加载时，也许已经有软件在播放声音了。比如iPod，或是Safari播放流媒体。下面这段代码能在App加载前检测有没有程序在占用音频输出资源。

UInt32 otherAudioIsPlaying;                                   // 1
UInt32 propertySize = sizeof (otherAudioIsPlaying);
 
AudioSessionGetProperty (                                     // 2
    kAudioSessionProperty_OtherAudioIsPlaying,
    &propertySize,
    &otherAudioIsPlaying
);
 
if (otherAudioIsPlaying) {                                    // 3
    [[AVAudioSession sharedInstance]
                    setCategory: AVAudioSessionCategoryAmbient
                          error: nil];
} else {
    [[AVAudioSession sharedInstance]
                    setCategory: AVAudioSessionCategorySoloAmbient
                          error: nil];
}