我想用我将要执行的程序播放mp3文件。我可以播放文件而无需下载文件，但我无法播放我下载的文件。你能帮我解决这个问题吗？
我正在研究Xamarin.Forms项目。我通过API从互联网上下载mp3文件。但我无法弄清楚下载文件的具体注册位置。我分享了我在IOS层和PCL一侧写的代码。
注意：我可以检查下载是否成功并检查下载状态。
注意2：我使用Xam.Plugins.DownloadManager进行下载。
我在IOS层写的代码。
public void SetDownloadPath()
{
CrossDownloadManager.Current.PathNameForDownloadedFile = new System.Func<IDownloadFile, string>(file =>
{
string fileName = (new NSUrl(file.Url, false)).LastPathComponent;
return Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments), fileName);
});
}
我在ViewModel中编写的代码。
public async Task<DownloadItem> AddBookDownload(BookInfo _bookInfo)
{
var downloadItem = new DownloadItem
{
BookName = _bookInfo.Title,
DownloadID = _bookInfo.ID,
DistinctionCount = _bookInfo.SectionCount
};
var sections = await LibraryClient.GetBookSections(_bookInfo.ID);
downloadItem.Sections = sections.Data;
if (downloadItem.Sections == null || downloadItem.Sections.Count <0)
{
return null;
}
var linkFile =
CrossDownloadManager.Current.CreateDownloadFile(downloadItem.Sections.FirstOrDefault()
?.GetLink()
.ToString());
downloadItem.DownloadedTaskList.Add(linkFile.GetHashCode(), downloadItem);
linkFile.PropertyChanged += (sender, e) =>
{
// Update UI text-fields
var downloadFile = (IDownloadFile) sender;
switch (e.PropertyName)
{
case nameof(IDownloadFile.Status):
Device.BeginInvokeOnMainThread(() =>
{
downloadItem.DownloadState = downloadFile.Status;
Debug.WriteLine("Download Status: " + downloadFile.Status);
});
break;
case nameof(IDownloadFile.StatusDetails):
Device.BeginInvokeOnMainThread(() =>
{
Debug.WriteLine("Download Details: " + downloadFile.StatusDetails);
});
break;
case nameof(IDownloadFile.TotalBytesExpected):
Device.BeginInvokeOnMainThread(() =>
{
Debug.WriteLine("BytesExpected" + downloadFile.TotalBytesExpected);
});
break;
case nameof(IDownloadFile.TotalBytesWritten):
Device.BeginInvokeOnMainThread(() =>
{
Debug.WriteLine("BytesWritten" + downloadFile.TotalBytesWritten);
});
break;
}
// Update UI if download-status changed.
if (e.PropertyName == "Status")
switch (((IDownloadFile) sender).Status)
{
case DownloadFileStatus.COMPLETED:
downloadItem.DownloadState = DownloadFileStatus.COMPLETED;
DistinctionCount = downloadItem.DistinctionCount;
BookName = downloadItem.BookName;
DownloadedBooks.Add(downloadItem);
NativeServices.DownloadService.SaveDownloadsItem(downloadItem);
NativeServices.MediaPlayerService.PlayFromFile(Path.GetFileName(CrossDownloadManager.Current.PathNameForDownloadedFile.ToString()));
Debug.WriteLine("Download Completed");
break;
case DownloadFileStatus.FAILED:
downloadItem.DownloadState = DownloadFileStatus.FAILED;
Debug.WriteLine("Download Failed");
break;
case DownloadFileStatus.CANCELED:
Device.BeginInvokeOnMainThread(() => { Debug.WriteLine("Download Cancelled"); });
break;
}
// Update UI while donwloading.
if (e.PropertyName == "TotalBytesWritten" || e.PropertyName == "TotalBytesExpected")
{
var bytesExpected = ((IDownloadFile) sender).TotalBytesExpected;
var bytesWritten = ((IDownloadFile) sender).TotalBytesWritten;
if (bytesExpected > 0)
{
var percentage = Math.Round(bytesWritten / bytesExpected * 100);
Device.BeginInvokeOnMainThread(() => { Debug.WriteLine("Downloading" + percentage + "%"); });
}
}
};
CrossDownloadManager.Current.Start(linkFile);
return downloadItem;
}