我正在使用背景文件传输和背景音频播放器。在TransferStatusChanged事件中，我将文件保存到独立存储，然后用音频播放器播放，
如果该应用程序处于活动状态，则可以正常工作；如果该应用程序处于非活动状态，我也想这样做。
在WP8.0中，由于您TransferStatusChanged正处于App进程中，当您离开它时，该进程将停止，这是不可能的：
当引发Deactivated事件后，当用户离开应用程序向前导航时，操作系统将尝试将应用程序置于休眠状态。在这种状态下，所有应用程序线程都将停止并且不进行任何处理，但是应用程序在内存中保持不变。
您可以通过禁用IdleDetection使其在LockScreen下工作，但是当您的应用程序进入休眠/逻辑删除状态时，它将无法工作。
您可以考虑在激活应用程序时开始播放，或者在BAP中放入一些逻辑，例如可以在TrackChange上检查文件是否已下载然后播放。
@Romasz建议在文件完全下载时使用空轨道播放，然后进行编辑，然后在TrackChange中检查是否已下载文件并将其从下载队列中删除-这可以在音频背景中完成-现在一切正常。这是一些代码
private AudioTrack GetNextTrack(bool isStart = false)
{
AudioTrack track = null;
using (IsolatedStorageFile ISF = IsolatedStorageFile.GetUserStoreForApplication())
{
if (isStart)
{
currentSongIndex = -1;
}
currentSongIndex++;
if (currentSongIndex == _ProgressList.Count())
{
//currentSongIndex = 0;
return track;
}
if (ISF.FileExists("shared/transfers/" + _ProgressList[currentSongIndex].FileName))
{
var request = requests.Where(it => it.Key == _ProgressList[currentSongIndex].FileName).FirstOrDefault().Value;
if (request != null)
{
bool isDone = ProcessTransfer(request, _ProgressList[currentSongIndex].Directory);
if(!isDone )
{
if(request.BytesReceived > LastDownloadedSize)
{
NumberOfTrialsToLoadNextTrack = 0;
LastDownloadedSize = request.BytesReceived;
}
else
{
++NumberOfTrialsToLoadNextTrack;
}
}
}
}
else
{
++NumberOfTrialsToLoadNextTrack;
}
if (ISF.FileExists(_ProgressList[currentSongIndex].Directory+_ProgressList[currentSongIndex].FileName))
{
track = playList[currentSongIndex];
NumberOfTrialsToLoadNextTrack = 0;
LastDownloadedSize = 0;
}
else
{
currentSongIndex--;
if (NumberOfTrialsToLoadNextTrack < 10)
{
track = new AudioTrack(new Uri("halfsec.mp3", UriKind.Relative),
"empty",
"empty",
"empty",
null);
}
}
}
return track;
}
private bool ProcessTransfer(BackgroundTransferRequest transfer, string directory = "")
{
bool isDone = false;
switch (transfer.TransferStatus)
{
case TransferStatus.Completed:
if (transfer.StatusCode == 200 || transfer.StatusCode == 206)
{
RemoveTransferRequest(transfer.RequestId);
using (IsolatedStorageFile isoStore = IsolatedStorageFile.GetUserStoreForApplication())
{
string filename = transfer.Tag;
System.Diagnostics.Debug.WriteLine(directory + filename);
if (isoStore.FileExists(directory + filename))
{
isoStore.DeleteFile(directory + filename);
}
if (isoStore.FileExists(transfer.DownloadLocation.OriginalString))
{
isoStore.MoveFile(transfer.DownloadLocation.OriginalString, directory + filename);
}
}
isDone = true;
}
else
{
RemoveTransferRequest(transfer.RequestId);
if (transfer.TransferError != null)
{
}
}
break;
}
return isDone;
// NotifyComplete();
}
private void RemoveTransferRequest(string transferID)
{
// Use Find to retrieve the transfer request with the specified ID.
BackgroundTransferRequest transferToRemove = BackgroundTransferService.Find(transferID);
// try to remove the transfer from the background transfer service.
try
{
BackgroundTransferService.Remove(transferToRemove);
}
catch (Exception)
{
}
}
protected override void OnPlayStateChanged(BackgroundAudioPlayer player, AudioTrack track, PlayState playState)
{
switch (playState)
{
case PlayState.TrackEnded:
player.Track = GetNextTrack();
break;
case PlayState.TrackReady:
player.Play();
break;
case PlayState.Shutdown:
// TODO: Handle the shutdown state here (e.g. save state)
break;
case PlayState.Unknown:
break;
case PlayState.Stopped:
break;
case PlayState.Paused:
break;
case PlayState.Playing:
break;
case PlayState.BufferingStarted:
break;
case PlayState.BufferingStopped:
break;
case PlayState.Rewinding:
break;
case PlayState.FastForwarding:
break;
}
NotifyComplete();
}
此代码在AudioPlayer类中，文件通常添加到xaml.cs的下载队列中
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