Windows 8 Store Apps Learning (66) Background tasks: Downloading and uploading

Introduced

Re-imagine Windows 8 Store Apps after a task

Background Download Task

Background upload Task

Example

Extended downloadoperation and uploadoperation so that download progress or upload progress can be notified

Backgroundtask/transfermodel.cs

* * Extended downloadoperation and uploadoperation for download progress or upload progress to notify/using System;
Using System.ComponentModel;
    
Using Windows.Networking.BackgroundTransfer; Namespace Xamldemo.backgroundtask {public class Transfermodel:inotifypropertychanged {public Downloado
        Peration 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)); }
        }
    }
}

1. Demo Background Download task application

Backgroundtask/transferdownload.xaml

<page x:class= "XamlDemo.BackgroundTask.TransferDownload" xmlns= "http://schemas.microsoft.com/winfx/2006/xaml/
    Presentation "xmlns:x=" Http://schemas.microsoft.com/winfx/2006/xaml "xmlns:local=" Using:XamlDemo.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= "0 0 0" > <scrollviewer height= "> <textblock name=" lblmsg "Font Size= "14.667" textwrapping= "Wrap"/> </ScrollViewer> <button name= "Btnadddownloa D "content=" New Download Task "margin=" 0 0 0 "click=" Btnadddownload_click "/> <button name=" Btnpause "Content = "Suspend all download Tasks" margin= "0 0 0" click= "Btnpause_click"/> <button name= "Btnresume" content= "continue all download Tasks" Mar gin= "0 0 0" click= "btnresume_click "/> <button name=" Btncancel content= "Cancel all download Tasks" margin= "0 0 0" click= "Btncancel_click"/> <listview name= "ListView" padding= "0 0 0" height= "> &LT;LISTVIEW.ITEMTEMPLATE&G"
                    T
                            <DataTemplate> <stackpanel margin= "0 5" background= "Blue" > <textblock text= "{Binding Source}" margin= "5"/> <textblock text= "{Binding Destinat
                        Ion} "margin=" 5 "/> <textblock text=" {Binding Progress} "margin=" 5 "/>
            </StackPanel> </DataTemplate> </ListView.ItemTemplate> </ListView> </StackPanel> </Grid> </Page>

Backgroundtask/transferdownload.xaml.cs

* * Demo Background Download Task Application * * Backgrounddownloader-Background Download Task Manager * costpolicy-Download cost policy, Backgroundtransfercostpolicy enumeration * Default-do not allow transmission on high cost (e.g. 2G 3G) network * unrestrictedonly-allows transmission on high cost (such as 2G 3G) network Always-can be transmitted in any case,  Even when roaming * servercredential-credentials * proxycredential when communicating with the server-the identity credentials * setRequestHeader (string headername) when the proxy is used  String headervalue)-Set HTTP request header * Createdownload (URI Uri, Istoragefile resultfile)-Create a download task, return to Downloadoperation Object * Group-for group download task * Static Getcurrentdownloadsasync (string group)-Gets all download tasks under the specified group * static GETCURRENTD Ownloadsasync ()-Get all download tasks not associated with the group * downloadoperation-Download Task Object * costpolicy-Download cost policy, BACKGROUNDTRANSFERCOSTP      Olicy enum * Group-Gets the group * Guid for this download task-Gets the identity of this download task * Requesteduri-Download Source URI * resultfile-Download target file * Getresponseinformation ()-The server-side response information obtained after the download is complete, returns the Responseinformation object * Actualuri-the true URI of the download source * He Aders-HTTP headers for server-side responses *         StatusCode-server-side response status code * PAUSE ()-Pause this task * Resume ()-Continue this task * Startasync ()-Add a download task, return to Iasyncope Rationwithprogress<downloadoperation, downloadoperation> Object * Attachasync ()-Monitors existing download tasks, returns Iasyncoperationwith     
 Progress<downloadoperation, downloadoperation> Object * Progress-Get download progress, return backgrounddownloadprogress Object * * backgrounddownloadprogress-Background Download Task download Progress Object * bytesreceived-Number of bytes downloaded * totalbytestoreceive-the total number of bytes to download, unknown to 0 * Status-download status, backgroundtransferstatus enum * Idle, Running, Pausedbyapplication, Pausedcostednetwork, Pa Usednonetwork, Completed, Canceled, Error * hasresponsechanged-Server response is true * hasrestarted-after the current load connection is broken, the system passes through H
The TTP range header continues to request a breakpoint on the server, and if the service side does not support a breakpoint continuation, it needs to be downloaded again, which is true/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;
        Namespace Xamldemo.backgroundtask {public sealed partial class Transferdownload:page {//Download task collection
    
        Private observablecollection<transfermodel> _transfers = new observablecollection<transfermodel> (); The associated CancellationTokenSource object for all download tasks is private CancellationTokenSource _canceltoken = new Cancellationtok
           
        Ensource (); Public Transferdownload () {this.
    
            InitializeComponent ();
        Init ();
    
            Private async void Init () {listview.itemssource = _transfers;
        Get all download tasks await loaddownloadasync (); //load all download Tasks Private Async Task Loaddownloadasync () {Ireadonlylist<downloado
            Peration> downloads = null;
      try {//Get all background download tasks          Downloads = await backgrounddownloader.getcurrentdownloadsasync (); catch (Exception ex) {lblmsg.text = ex.
                ToString ();
                Lblmsg.text + = Environment.NewLine;
            Return } if (downloads.
                Count > 0) {list<task> tasks = new list<task> ();
                    foreach (downloadoperation download in downloads) {//monitor specified background download task Tasks.
                Add (Handledownloadasync (download, false));
            } await Task.whenall (tasks);
        }//Add a download task private async void Btnadddownload_click (object sender, RoutedEventArgs e) {///download address (note that you need to add package.appxmanifest to. rar type files)//View more highlights of this column: HTTP://WWW.BIANCENG.CNHTTP://WW W.bianceng.cn/programming/net/uri Sourceuri = new Uri ("http://files.cnblogs.com/webabcd/windows8.rar ", Urikind.absolute);
            Storagefile Destinationfile; try {//saved destination Address Destinationfile = await KnownFolders.DocumentsLibrary.CreateF
            Ileasync ("Windows8.rar", creationcollisionoption.generateuniquename); catch (Exception ex) {lblmsg.text = ex.
                ToString ();
                Lblmsg.text + = Environment.NewLine;
            Return
            //Create a background download task Backgrounddownloader Backgrounddownloader = new Backgrounddownloader ();
    
            downloadoperation download = backgrounddownloader.createdownload (Sourceuri, destinationfile);
        Monitors the specified background download task await Handledownloadasync (download, true); ///<summary>///Monitoring of the specified background download task///</summary>///<param name= "Downlo Ad "> Background download task </param>///<param name=" IsNew "> is newTask </param> Private Async Task Handledownloadasync (downloadoperation download, bool isnew) { try {//attach downloadoperation to Transfermodel so that the download progress can be notified Transfermodel tra
                Nsfer = new Transfermodel (); Transfer.
                downloadoperation = download; Transfer. Source = download.
                Requesteduri.tostring (); Transfer. Destination = download.
                Resultfile.path; Transfer.
    
                Progress = "0/0"; _transfers.
    
                ADD (transfer); Lblmsg.text = "Task Count:" + _transfers.
                Count.tostring ();
    
                Lblmsg.text + = Environment.NewLine; callback function Progress<downloadoperation> Progresscallback = new progress<downloadoperation& When download progress is changed
    
                gt; (downloadprogress); if (isnew) await download. Startasync (). Astask (_canceltoken.token, progresscallback);
       Add a background download task         else await download. Attachasync (). Astask (_canceltoken.token, progresscallback); Monitor the existing background download task//Get the response information for the server after the download is complete responseinformation response = download.
                Getresponseinformation (); Lblmsg.text + = "Completed:" + response. Actualuri + "-" + response.
                Statuscode.tostring ();
            Lblmsg.text + = Environment.NewLine; A catch (taskcanceledexception)//Call to Cancellationtokensource.cancel () throws this exception {L Blmsg.text + = "Canceled:" + download.
                Guid;
            Lblmsg.text + = Environment.NewLine; A catch (Exception ex) {//Converts an exception to a Weberrorstatus enumeration, if the Weberrorstatus.unknow is obtained n indicates that this exception is not a Web-related exception weberrorstatus error = Backgroundtransfererror.getstatus (ex.
    
                HResult); Lblmsg.text = ex.
                ToString ();
            Lblmsg.text + = Environment.NewLine;
      }      finally {_transfers. Remove (_transfers.
            (p => p.downloadoperation = = download)); }//Progress changes, update Transfermodel Progress to notify private void DownloadProgress (Downloadoperati on download) {Transfermodel transfer = _transfers.
            A (p => p.downloadoperation = = download); Transfer. Progress = download. Progress.BytesReceived.ToString ("#,0") + "/" + download.
        Progress.TotalBytesToReceive.ToString ("#,0"); //Pause all background download task private void Btnpause_click (object sender, RoutedEventArgs e) {L
            Blmsg.text + = "All paused";
            Lblmsg.text + = Environment.NewLine; foreach (Transfermodel transfer in _transfers) {if (transfer. DownloadOperation.Progress.Status = = backgroundtransferstatus.running) {transfer.
                Downloadoperation.pause ();
         }   }//Continue all background download tasks private void Btnresume_click (object sender, RoutedEventArgs e) {
            Lblmsg.text + = "all resumed";
            Lblmsg.text + = Environment.NewLine; foreach (Transfermodel transfer in _transfers) {if (transfer. DownloadOperation.Progress.Status = = backgroundtransferstatus.pausedbyapplication) {T Ransfer.
                Downloadoperation.resume (); //Cancel all background download task private void Btncancel_click (object sender, RoutedEventArgs E
            ) {_canceltoken.cancel ();
    
            _canceltoken.dispose ();
        _canceltoken = new CancellationTokenSource (); }
    }
}

2, Demo background upload task application

Backgroundtask/transferupload.xaml