需要在播放的时候,设置一下session 的属性。
UInt32 allowMix = 1;
AVAudioSession* audioSession = [AVAudioSession sharedInstance];
[audioSession setCategory:AVAudioSessionCategoryPlayback error:nil];
AudioSessionSetProperty(kAudioSessionProperty_OverrideCategoryMixWithOthers, sizeof(allowMix), &allowMix);
[audioSession setActive:YES error:nil];