当开始播放时压低其他app的声音，播放结束后恢复正常
//MARK: 开始播放音效
[[soundBtn rac_signalForControlEvents:UIControlEventTouchUpInside] subscribeNext:^(UIButton * value) {
NSError * setCategoryError = nil;
if(![[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryAmbient withOptions:AVAudioSessionCategoryOptionDuckOthers error:&setCategoryError]){
[SVProgressHUD showErrorWithStatus:@"音效文件已损坏，请重新上传"];
}else{
[[AVAudioSession sharedInstance] setActive:YES error:nil];
[_audioPlayer play];
[value.imageView startAnimating];
}
}];
//MARK: 停止播放音效
[[self rac_signalForSelector:@selector(audioPlayerDidFinishPlaying:successfully:) fromProtocol:@protocol(AVAudioPlayerDelegate)] subscribeNext:^(id x) {
[[AVAudioSession sharedInstance] setActive:NO withOptions:AVAudioSessionSetActiveOptionNotifyOthersOnDeactivation error:nil];
[_audioPlayer stop];
[soundBtn.imageView stopAnimating];
}];
