iOS-在多任务栏中更新媒体播放/暂停状态

Question

我们有一个使用AU graph - CoreAudio API的工作应用程序来播放音频。图形始终在运行，各种源素材的播放/暂停状态在图形渲染回调函数中管理。我们成功地响应了UIEventTypeRemoteControl事件，并使用MPNowPlayingInfoCenter使用当前播放内容的元数据成功地更新了锁定屏幕。

缺少的一点是更新iOS多任务处理栏中播放/暂停按钮的状态。它始终处于“暂停”（||）模式，即使应用程序音频已经暂停。它从不切换到“播放”(

哪个API用于更新播放/暂停按钮状态？

Answer 1

更改MPNowPlayingInfo字典，设置新参数

MPNowPlayingInfoPropertyPlaybackRate to 1.0f to show pause button

MPNowPlayingInfoPropertyPlaybackRate to 0.0f to show play button

从播放按钮到暂停按钮

Class playingInfoCenter = NSClassFromString(@"MPNowPlayingInfoCenter");
if(playingInfoCenter) {       
    NSMutableDictionary *songInfo = [NSMutableDictionary dictionaryWithDictionary:[MPNowPlayingInfoCenter defaultCenter].nowPlayingInfo];
    //[songInfo setObject:songTitle forKey:MPMediaItemPropertyTitle];
    //[songInfo setObject:songArtist forKey:MPMediaItemPropertyArtist];
    [songInfo setObject:[NSNumber numberWithFloat:1.0f] forKey:MPNowPlayingInfoPropertyPlaybackRate];
    [MPNowPlayingInfoCenter defaultCenter].nowPlayingInfo = songInfo;            
 }

从暂停按钮 - 到 - 播放按钮

Class playingInfoCenter = NSClassFromString(@"MPNowPlayingInfoCenter");
if(playingInfoCenter) {         
    NSMutableDictionary *songInfo = [NSMutableDictionary dictionaryWithDictionary:[MPNowPlayingInfoCenter defaultCenter].nowPlayingInfo];
    //[songInfo setObject:songTitle forKey:MPMediaItemPropertyTitle];
    //[songInfo setObject:songArtist forKey:MPMediaItemPropertyArtist];
    [songInfo setObject:[NSNumber numberWithFloat:0.0f] forKey:MPNowPlayingInfoPropertyPlaybackRate];
    [MPNowPlayingInfoCenter defaultCenter].nowPlayingInfo = songInfo;
}

Answer 2

我发现当使用CoreAudio AU图时，AUGraphStart（）将在iOS状态栏和iOS多任务栏中显示回放指示器，AUGraphStation（）将清除它们。