/// <summary>
/// 后台任务的入口方法
/// </summary>
/// <param name="taskInstance">表示当前任务的实例</param>
public void Run(IBackgroundTaskInstance taskInstance)
{
//初始化后台消息处理的线程锁
o = new object();
//初始化系统音频控制器
smtc = BackgroundMediaPlayer.Current.SystemMediaTransportControls;
smtc.ButtonPressed += Smtc_ButtonPressed;
smtc.PropertyChanged += Smtc_PropertyChanged;
smtc.IsEnabled = true;
smtc.IsNextEnabled = true;
smtc.IsPreviousEnabled = true;
smtc.IsPlayEnabled = true;
smtc.IsPauseEnabled = true;
//获取前台APP状态
var appState = BackgroundAudioSettingsHelper.GetValue(BackgroundAudioSettingsConstants.APP_STATE);
if (appState == null)
{
foregroundAppState = AppState.Unknown;
}
else
{
foregroundAppState = EnumHelper.Parse <AppState>(appState.ToString());
}
//注册后台播放器的状态改变事件
BackgroundMediaPlayer.Current.CurrentStateChanged += Current_CurrentStateChanged;
//注册后台播放器发生错误时的事件
BackgroundMediaPlayer.Current.MediaFailed += Current_MediaFailed;
BackgroundMediaPlayer.Current.MediaEnded += Current_MediaEnded;
//注册后台播放器接收前台消息事件
BackgroundMediaPlayer.MessageReceivedFromForeground += BackgroundMediaPlayer_MessageReceivedFromForeground;
//如果前台APP未处于挂起状态，发送后台音频启动消息给前台
if (foregroundAppState != AppState.Suspended)
{
MessageService.SendMessageToForeground(new BackgroundAudioTaskStartedMessage());
}
//保存后台音频任务的启动状态
BackgroundAudioSettingsHelper.SetValue(BackgroundAudioSettingsConstants.BACKGROUND_TASK_STATE, BackgroundTaskState.Running.ToString());
deferral = taskInstance.GetDeferral();
backgroundTaskStarted.Set();
//注册后台任务结束事件
taskInstance.Task.Completed += Task_Completed;
//注册后台任务取消事件
taskInstance.Canceled += TaskInstance_Canceled;
}
/// <summary>
/// 开始播放音乐。
/// 如果是第一次启动播放，直接播放；如果不是第一次启动播放，需要跳转到上次保存的进度继续播放。
/// </summary>
//private void StartPlayback()
//{
// try
// {
// BackgroundMediaPlayer.Current.Source = playbackList;
// var currentTrackIndex = BackgroundAudioSettingsHelper.GetValue(BackgroundAudioSettingsConstants.TRACK_INDEX);
// var currentTrackPosition = BackgroundAudioSettingsHelper.GetValue(BackgroundAudioSettingsConstants.POSITION);
// if (!isFirstTimeToStart)
// {
// uint index;
// if (currentTrackIndex != null && uint.TryParse(currentTrackIndex.ToString(), out index))
// {
// currentIndex = (int)index;
// if (currentTrackPosition == null)
// {
// playbackList.MoveTo(index);
// BackgroundMediaPlayer.Current.Play();
// }
// else
// {
// TypedEventHandler<MediaPlaybackList, CurrentMediaPlaybackItemChangedEventArgs> handler = null;
// handler =
// (MediaPlaybackList list, CurrentMediaPlaybackItemChangedEventArgs args) =>
// {
// try
// {
// if (args.NewItem.Equals(playbackList.Items[(int)index]))
// {
// playbackList.CurrentItemChanged -= handler;
// var position = TimeSpan.Parse((string)currentTrackPosition);
// BackgroundMediaPlayer.Current.Position = position;
// BackgroundMediaPlayer.Current.Play();
// }
// }
// catch
// {
// }
// };
// playbackList.CurrentItemChanged += handler;
// playbackList.MoveTo(index);
// }
// }
// else
// {
// BackgroundMediaPlayer.Current.Play();
// }
// }
// else
// {
// BackgroundMediaPlayer.Current.Play();
// isFirstTimeToStart = false;
// }
// }
// catch (Exception ex)
// {
// Debug.WriteLine(ex.ToString() + " " + ex.Message);
// }
//}
private void StartPlayback()
{
try
{
var currentTrackIndex = BackgroundAudioSettingsHelper.GetValue(BackgroundAudioSettingsConstants.TRACK_INDEX);
var positionSetting = BackgroundAudioSettingsHelper.GetValue(BackgroundAudioSettingsConstants.POSITION);
if (!isFirstTimeToStart)
{
int index;
if (currentTrackIndex != null && int.TryParse(currentTrackIndex.ToString(), out index))
{
if (positionSetting == null)
{
PlayIndex(index);
}
else
{
var position = TimeSpan.Parse((string)positionSetting);
PlayIndexWithPosition(index, position);
}
}
else
{
PlayIndex(0);
}
}
else
{
PlayIndex(0);
}
}
catch (Exception)
{
throw;
}
}