wp wp8:后台传输服务

1.TransferPreferences属性设置：

后台传输服务上传最大文件大小为5M

通过手机网络连接最大下载大小为20M，若超过此大小，属性将自动更改为AllowBattery

通过wifi没有外部电源最大下载大小为100M，若超过此大小，属性设置为None

2.每个应用程序队列中未完成的最大请求个数为25个，最大并发数为2个，对大排队传输数位500

3.网络连接数组3G网络低于50kbps，wifi/usb网络低于100kbps会暂停传输并重试





上代码：

MainPage.xaml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Navigation;
using Microsoft.Phone.Controls;
using Microsoft.Phone.Shell;
using wp8BackgroundTransfer.Resources;
using Microsoft.Phone.BackgroundTransfer;

namespace wp8BackgroundTransfer
{
    public partial class MainPage : PhoneApplicationPage
    {
        // 构造函数
        public MainPage()
        {
            InitializeComponent();

          
        }

        BackgroundTransferRequest transferRequest;

        private void download_click(object sender, System.Windows.RoutedEventArgs e)
        {

            if (BackgroundTransferService.Requests.Count() > 25)
            {
                return;
            }

            String transferFileName = "http://m.news.cn/version_wp8.txt";
            Uri transferUri;
            try
            {
                transferUri = new Uri(Uri.EscapeUriString(transferFileName), UriKind.RelativeOrAbsolute);
            }
            catch
            {
                return;
            }

            transferRequest = new BackgroundTransferRequest(transferUri);

            transferRequest.TransferPreferences = TransferPreferences.None;

            transferRequest.TransferProgressChanged += new EventHandler<BackgroundTransferEventArgs>(transfer_TransferProgressChanged);

            transferRequest.TransferStatusChanged += new EventHandler<BackgroundTransferEventArgs>(transfer_TransferStatusChanged);

            transferRequest.Method = "GET";

            string downloadFileName = transferFileName.Substring(transferFileName.LastIndexOf("/")+1);

            Uri downloadUri = new Uri("shared/transfers/"+ downloadFileName, UriKind.RelativeOrAbsolute);

            transferRequest.DownloadLocation = downloadUri;

            transferRequest.Tag = downloadFileName;

            try
            {
                BackgroundTransferService.Add(transferRequest);
            }
            catch
            {
                return;
            }

        }

        private void cancel_click(object sender, System.Windows.RoutedEventArgs e)
        {

            if(transferRequest != null)
                removeRequest(transferRequest.RequestId);

        }

        void transfer_TransferProgressChanged(object sender, BackgroundTransferEventArgs e)
        {
           
        }

        void transfer_TransferStatusChanged(object sender, BackgroundTransferEventArgs e)
        {
            BackgroundTransferRequest transfer = e.Request;

            switch (transfer.TransferStatus)
            {
                case TransferStatus.Completed:
                    {
                        if (transfer.StatusCode == 200 || transfer.StatusCode == 206)
                        {
                            removeRequest(transfer.RequestId);
                        }
                        else
                        {
                            removeRequest(transfer.RequestId);
                            if (transfer.TransferError != null)
                            {
                                System.Diagnostics.Debug.WriteLine("失败："+transfer.TransferError);
                            }
                        }
                    }
                    break;
                case TransferStatus.WaitingForExternalPower:
                    {
                        System.Diagnostics.Debug.WriteLine("电力不足，不能启动");
                    }
                    break;
                case TransferStatus.WaitingForExternalPowerDueToBatterySaverMode:
                    {
                        System.Diagnostics.Debug.WriteLine("省电模式，不能启动");
                    }
                    break;
                case TransferStatus.WaitingForNonVoiceBlockingNetwork:
                    {
                        System.Diagnostics.Debug.WriteLine("等待网络");
                    }
                    break;
                case TransferStatus.WaitingForWiFi:
                    {
                        System.Diagnostics.Debug.WriteLine("等待wifi网络");
                    }
                    break;
            }
        }

        void removeRequest(string id)
        {
            BackgroundTransferRequest request = BackgroundTransferService.Find(id);
            if (request != null)
            {
                BackgroundTransferService.Remove(request);
            }
        }
       
    }
}

MainPage.xaml

<phone:PhoneApplicationPage
    x:Class="wp8BackgroundTransfer.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:phone="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone"
    xmlns:shell="clr-namespace:Microsoft.Phone.Shell;assembly=Microsoft.Phone"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d"
    FontFamily="{StaticResource PhoneFontFamilyNormal}"
    FontSize="{StaticResource PhoneFontSizeNormal}"
    Foreground="{StaticResource PhoneForegroundBrush}"
    SupportedOrientations="Portrait" Orientation="Portrait"
    shell:SystemTray.IsVisible="True">

    <!--LayoutRoot 是包含所有页面内容的根网格-->
    <Grid x:Name="LayoutRoot" Background="Transparent">
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>


        <StackPanel Orientation="Vertical">


            <Button Content="download" Width="300" Height="100" Click="download_click"></Button>
            <Button Content="cancel" Width="300" Height="100" Click="cancel_click"></Button>
           
        </StackPanel>


    </Grid>

</phone:PhoneApplicationPage>