win8 Downlod mp3

前台代码:

 <Page.Resources>         <Style TargetType="TextBlock">             <Setter Property="FontSize" Value="27"/>             <Setter Property="FontFamily" Value="宋体"/>         </Style>     </Page.Resources>

    <Grid Background="{StaticResource ApplicationPageBackgroundThemeBrush}">

        <Grid.RowDefinitions>             <RowDefinition Height="auto"/>             <RowDefinition Height="*"/>         </Grid.RowDefinitions>                 <StackPanel Grid.Row="0" Margin="15,8" Orientation="Horizontal">             <TextBlock Text="输入下载URI：" VerticalAlignment="Center" />             <TextBox x:Name="txtInputUri" Width="680"/>             <Button x:Name="btnDown" Margin="38,0,0,0" VerticalAlignment="Center" Content="开始下载" Padding="17,5,17,5" FontSize="22" Click="onDownload_Click"/>         </StackPanel>                 <StackPanel Grid.Row="1" Margin="20">             <ProgressBar x:Name="probar" Maximum="100" Minimum="0" SmallChange="1" Width="700" HorizontalAlignment="Left" Foreground="Yellow"                         Height="30" Margin="6,21,0,35"/>             <TextBlock x:Name="tbMsg" Margin="6,8,0,0" />         </StackPanel>

    </Grid> < /Page>

后台代码:

using System; using System.Collections.Generic; using System.IO; using System.Linq; using Windows.Foundation; using Windows.Foundation.Collections; using Windows.Networking.BackgroundTransfer; using Windows.Storage; using Windows.Storage.Pickers; using Windows.UI.Xaml; using Windows.UI.Xaml.Controls; using Windows.UI.Xaml.Controls.Primitives; using Windows.UI.Xaml.Data; using Windows.UI.Xaml.Input; using Windows.UI.Xaml.Media; using Windows.UI.Xaml.Navigation;

// “空白页”项模板在 http://go.microsoft.com/fwlink/?LinkId=234238 上有介绍

namespace downLoad {     /// <summary>     /// 可用于自身或导航至 Frame 内部的空白页。     /// </summary>     public sealed partial class MainPage : Page     {         public MainPage()         {             this.InitializeComponent();         }

        /// <summary>         /// 在此页将要在 Frame 中显示时进行调用。         /// </summary>         /// <param name="e">描述如何访问此页的事件数据。Parameter         /// 属性通常用于配置页。</param>         protected override void OnNavigatedTo(NavigationEventArgs e)         {         }

        private async void onDownload_Click(object sender, RoutedEventArgs e)         {             // 判断是否已输入下载URI             if (string.IsNullOrWhiteSpace(this.txtInputUri.Text)) return;              // 选择文件保存位置             FileSavePicker picker = new FileSavePicker();              picker.FileTypeChoices.Add("MP3文件", new string[] { ".mp3" });              StorageFile file = await picker.PickSaveFileAsync();              if (file != null)              {                  // 实例化BackgroundDownloader                  BackgroundDownloader downloader = new BackgroundDownloader();                  DownloadOperation operation = downloader.CreateDownload(new Uri(this.txtInputUri.Text), file);                  // 进度                  Progress<DownloadOperation> progressDown = new Progress<DownloadOperation>(this.ProgressChanged);                  // 开始下载                  btnDown.IsEnabled = false;                  var opresult = await operation.StartAsync().AsTask(progressDown);                  btnDown.IsEnabled = true;                 // 判断下载结果                  switch (opresult.Progress.Status)                  {                      case BackgroundTransferStatus.Completed:                          tbMsg.Text = "下载已完成。";                          break;                      case BackgroundTransferStatus.Error:                          tbMsg.Text = "下载过程中发生了错误。";                          break;                      default:                          tbMsg.Text = "未知。";                          break;                  }              }          }

               /// <summary>          /// 报告进度          /// </summary>          private async void ProgressChanged(DownloadOperation op)          {              var p = op.Progress;              double t = p.TotalBytesToReceive;//要下载总字节数              double d = p.BytesReceived;//已接收字节数              // 计算完成百分比              double pc = d / t * 100;              await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, () =>                  {                      this.probar.Value = pc;                      this.tbMsg.Text = string.Format("已下载{0}字节/共{1}字节。", d.ToString("N0"), t.ToString("N0"));                  });          }

    } }