开发笔记:背水一战Windows10(118)后台任务:后台下载任务（任务分组，并行或串行执行，组完成后通知）

/*
* 扩展了 DownloadOperation 和 UploadOperation，用于 MVVM 绑定数据
*/
using System;
using System.ComponentModel;
using Windows.Networking.BackgroundTransfer;
namespace Windows10.BackgroundTask
{
public class TransferModel : INotifyPropertyChanged
{
public DownloadOperation DownloadOperation { get; set; }
public UploadOperation UploadOperation { get; set; }
public string Source { get; set; }
public string Destination { get; set; }
private string _progress;
public string Progress
{
get { return _progress; }
set
{
_progress = value;
RaisePropertyChanged("Progress");
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected void RaisePropertyChanged(string name)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(name));
}
}
}
}

<Page
x:Class="Windows10.BackgroundTask.TransferGroup"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:Windows10.BackgroundTask"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d">
<Grid Background="Transparent">
<StackPanel Margin="10 0 10 10">
<ScrollViewer Name="scrollViewer" Height="100" Margin="5">
<TextBlock Name="lblMsg" TextWrapping="Wrap" />
ScrollViewer>
<Button Name="btnAddDownload" Content="新增一组（3 个）下载任务，可以指定其是并发还是串行，当这一组的所有任务都完成后弹出通知" Margin="5" Click="btnAddDownload_Click" />
<Button Name="btnCancel" Content="取消所有下载任务" Margin="5" Click="btnCancel_Click" />
<ListView Name="listView" Height="286" Padding="5">
<ListView.ItemTemplate>
<DataTemplate>
<StackPanel Margin="0 5" Background="Blue">
<TextBlock Text="{Binding Source}" Margin="5" />
<TextBlock Text="{Binding Destination}" Margin="5" />
<TextBlock Text="{Binding Progress}" Margin="5" />
StackPanel>
DataTemplate>
ListView.ItemTemplate>
ListView>
StackPanel>
Grid>
Page>

/*
* 演示后台下载任务的分组，以及如何设置组内任务是并行执行还是串行执行，以及组任务全部完成后如何 toast 或 tile 通知）
*
* BackgroundTransferGroup - 后台下载任务的分组对象
* static BackgroundTransferGroup CreateGroup(string name) - 创建指定分组标识的 BackgroundTransferGroup 对象
* Name - 分组标识（只读）
* TransferBehavior - 组内下载任务的执行方式，BackgroundTransferBehavior 枚举
* Parallel - 并行
* Serialized - 串行
*
* BackgroundDownloader - 后台下载任务管理器
* TransferGroup - 设置或获取分组对象（BackgroundTransferGroup 类型）
* static GetCurrentDownloadsForTransferGroupAsync(BackgroundTransferGroup group) - 获取指定组的所有下载任务
*
* DownloadOperation - 下载任务对象
* TransferGroup - 获取此下载任务的分组对象（BackgroundTransferGroup 类型）
*/
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Threading;
using System.Threading.Tasks;
using System.Linq;
using Windows.Networking.BackgroundTransfer;
using Windows.Storage;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.Web;
using Windows.UI.Notifications;
using Windows.Data.Xml.Dom;
namespace Windows10.BackgroundTask
{
public sealed partial class TransferGroup : Page
{
// 用于后台任务的分组（通过组名标识后台任务）
private BackgroundTransferGroup _group = BackgroundTransferGroup.CreateGroup("my_group");
// 下载任务的集合
private ObservableCollection _transfers = new ObservableCollection();
// 所有下载任务的关联的 CancellationTokenSource 对象
private CancellationTokenSource _cancelToken = new CancellationTokenSource();
public TransferGroup()
{
this.InitializeComponent();
Init();
}
private async void Init()
{
// 指定组内任务并行执行
_group.TransferBehavior = BackgroundTransferBehavior.Parallel;
listView.ItemsSource = _transfers;
// 加载指定组的下载任务
await LoadDownloadAsync();
}
// 加载指定组的下载任务
private async Task LoadDownloadAsync()
{
IReadOnlyList downloads = null;
try
{
// 获取指定组的下载任务
downloads = await BackgroundDownloader.GetCurrentDownloadsForTransferGroupAsync(_group);
}
catch (Exception ex)
{
WriteLine(ex.ToString());
return;
}
if (downloads.Count > 0)
{
List tasks = new List();
foreach (DownloadOperation download in downloads)
{
// 监视指定的后台下载任务
tasks.Add(HandleDownloadAsync(download, false));
}
await Task.WhenAll(tasks);
}
}
// 新增一组（3 个）下载任务
private async void btnAddDownload_Click(object sender, RoutedEventArgs e)
{
BackgroundDownloader backgroundDownloader = new BackgroundDownloader();
// 指定分组
backgroundDownloader.TransferGroup = _group;
// 组任务全部成功后弹出指定的 toast 通知（类似的还有 SuccessTileNotification, FailureToastNotification, FailureTileNotification）
backgroundDownloader.SuccessToastNotification = GetToastNotification(_group.Name);
List downloads = new List();
for (int i = 0; i <3; i++)
{
Uri sourceUri = new Uri("http://files.cnblogs.com/webabcd/Windows10.rar", UriKind.Absolute);
StorageFile destinationFile;
try
{
// 保存的目标地址（别忘了在 Package.appxmanifest 中配置好 和 .rar 类型文件的关联）
StorageFolder storageFolder = await KnownFolders.GetFolderForUserAsync(null, KnownFolderId.DocumentsLibrary);
destinationFile = await storageFolder.CreateFileAsync("Windows10.rar", CreationCollisionOption.GenerateUniqueName);
}
catch (Exception ex)
{
WriteLine(ex.ToString());
return;
}
// 创建一个后台下载任务
DownloadOperation download = backgroundDownloader.CreateDownload(sourceUri, destinationFile);
downloads.Add(download);
}
// 处理并监视组内的后台下载任务
Task[] tasks = new Task[downloads.Count];
for (int i = 0; i )
{
tasks[i] = HandleDownloadAsync(downloads[i], true);
}
await Task.WhenAll(tasks);
}
///