Windows 8 Store Apps Learning (65) Background tasks: Background playback and control of music

Introduced

Re-imagine Windows 8 Store Apps after a task

Background playback and control of music

Example

An object to hold information about each piece of music

Backgroundtask/songmodel.cs

 * * * for the preservation of each piece of music related information * *
    
using System;
Using System.Threading.Tasks;
Using Windows.storage;
    
Namespace Xamldemo.backgroundtask
{public
    class Songmodel
    {
        ///<summary>
        ///music file
        ///</summary> public
        storagefile File;
    
        <summary>
        ///artist
        ///</summary> public
        string Artist;
    
        <summary>
        ///Music name
        ///</summary> public
        string Title;
    
        Public Songmodel (storagefile file)
        {
            file = file;
        }
    
        <summary>
        ///loaded Music related properties
        ///</summary> public
        async Task Loadmusicpropertiesasync ()
        {
            var properties = await this. File.Properties.GetMusicPropertiesAsync ();
    
            Artist = properties. Artist;
            Title = properties. Title;}}

Demonstrates how to perform background playback and control of music through Mediacontrol

Backgroundtask/mediacontroldemo.xaml

<page x:class= "XamlDemo.BackgroundTask.MediaControlDemo" 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" > <textblock name= "lblmsg" fontsize= "14.667"/>
            <button name= "Btnselectfiles" content= "select Files" click= "Btnselectfiles_click" margin= "0 0 0"/>
                <button name= "Btnplay" content= "Play" click= "Btnplay_click" margin= "0 0 0"/> <!-- In order for the music to play in the background, you need to set the MediaElement Audiocategory property to Backgroundcapablemedia--> <mediae Lement name= "MediaElement" Audiocategory= "Backgroundcapablemedia" autoplay= "False" mediaopened= "mediaelement_mediaopened" Mediaende 
    D= "mediaelement_mediaended" currentstatechanged= "mediaelement_currentstatechanged"/> </StackPanel> </Grid> </Page>

Backgroundtask/mediacontroldemo.cs

* * Demonstrates how to achieve background playback and control of music through Mediacontrol * * NOTE: * 1, need to add background task statement in Package.appxmanifest, and check "audio" * 2, need to MediaElement The Audiocategory property is set to Backgroundcapablemedia * * * Another: * Press the volume on the flat panel or the relevant buttons on the multimedia keyboard, pop-up background audio control box, through the Mediacontrol to monitor the user in this audio control box on the exercise
For the */using System;
Using System.Collections.Generic;
Using System.Threading.Tasks;
Using Windows.media;
Using Windows.storage;
Using Windows.Storage.Pickers;
Using Windows.Storage.Streams;
Using Windows.UI.Core;
Using Windows.UI.Xaml;
Using Windows.UI.Xaml.Controls;
    
Using Windows.UI.Xaml.Media; Namespace Xamldemo.backgroundtask {public sealed partial class Mediacontroldemo:page {private list< songmodel> _playlist = new list<songmodel> (); Background need to play the music list private int _currentsongindex = 0; Currently playing music private bool _previoustrackpressedregistered = false; Mediacontrol whether the Previoustrackpressed event is registered as private bool _nexttrackpressedregistered = false; Mediacontrol is registered NEXTTRACKPressed Event Public Mediacontroldemo () {this.
    
            InitializeComponent (); mediacontrol.playpausetogglepressed + = mediacontrol_playpausetogglepressed; Pressed the Play/pause key mediacontrol.playpressed + = mediacontrol_playpressed; Press the play key mediacontrol.pausepressed + = mediacontrol_pausepressed; Pressed the pause key mediacontrol.stoppressed + = mediacontrol_stoppressed; Press the Stop key mediacontrol.previoustrackpressed + = mediacontrol_previoustrackpressed; Pressed the "previous" key mediacontrol.nexttrackpressed + = mediacontrol_nexttrackpressed; Press the "Next" key mediacontrol.rewindpressed + = mediacontrol_rewindpressed; Press the "Fast Rewind" key mediacontrol.fastforwardpressed + = mediacontrol_fastforwardpressed; Press the "Fast Forward" key mediacontrol.soundlevelchanged + = mediacontrol_soundlevelchanged; Volume level has changed//mediacontrol.recordpressed + = mediacontrol_recordpressed;
            mediacontrol.channeldownpressed + = mediacontrol_channeldownpressed;
    
            mediacontrol.channeluppressed + = mediacontrol_channeluppressed; Mediacontrol.artistname; Currently playing the music of the artist//Mediacontrol.trackname; The name of the currently playing music//Mediacontrol.albumart; The path//Mediacontrol.isplaying of the album cover of the currently playing music; Whether the current music is playing//mediacontrol.soundlevel;
             The volume level of the currently played music (muted, low, full) _previoustrackpressedregistered = true;
        _nexttrackpressedregistered = true;
        ///press the Play/pause key on the Audio control box async void Mediacontrol_playpausetogglepressed (object sender, Object e) {if (mediacontrol.isplaying) {await dispatcher.runasync (COREDISPATCHERPR Iority.
                Normal, () => {mediaelement.pause ();
                });
         Await Outputmessage ("Play/pause pressed-pause");   else {await dispatcher.runasync (Coredispatcherpriority.normal, () =>
                {Mediaelement.play ();
                });
            Await Outputmessage ("Play/pause pressed-play");
        }///Press the play key on the audio control box async void Mediacontrol_playpressed (object sender, Object e) {await Dispatcher.runasync (Coredispatcherpriority.normal, () => {mediaelemen
            T.play ();
            });
        Await Outputmessage ("play pressed");
            ///Press the Pause key on the audio control box async void Mediacontrol_pausepressed (object sender, Object e) { Await Dispatcher.runasync (Windows.UI.Core.CoreDispatcherPriority.Normal, () => {Med
            Iaelement.pause ();
            });
        Await outputmessage ("Pause pressed"); ///press the STOP key on the audio control box async void MediacOntrol_stoppressed (object sender, Object e) {await dispatcher.runasync (Windows.UI.Core.CoreDispatcher
            Priority.normal, () => {mediaelement.stop ();
            });
        Await outputmessage ("Stop pressed"); 
            ///Press the previous key on the Audio control box async void Mediacontrol_previoustrackpressed (object sender, Object e) {
    
            Await Outputmessage ("Previous Track pressed");
                if (_currentsongindex > 0) {if (_currentsongindex = = (_playlist.count-1)) {if (!_nexttrackpressedregistered) {Mediacontrol.nextt
                        rackpressed + = mediacontrol_nexttrackpressed;
                    _nexttrackpressedregistered = true;
    
                }} _currentsongindex--; if (_currentsongindex = = 0) {mediacontrOl.
                    previoustrackpressed-= mediacontrol_previoustrackpressed;
                _nexttrackpressedregistered = false;
            } await Setcurrentplayingasync (_currentsongindex); The "Next" key on the Audio control box async void Mediacontrol_nexttrackpressed (object sender, Object E
    
            ) {await outputmessage ("Next Track pressed");
                if (_currentsongindex < (_playlist.count-1)) {_currentsongindex++;
    
                Await Setcurrentplayingasync (_currentsongindex);
                    if (_currentsongindex > 0) {if (!_previoustrackpressedregistered)
                        {mediacontrol.previoustrackpressed + = mediacontrol_previoustrackpressed;
                    _previoustrackpressedregistered = true; } if (_currentsongindex = = (_playlisT.count-1)) {if (_nexttrackpressedregistered) {
                        mediacontrol.nexttrackpressed-= mediacontrol_nexttrackpressed;
                    _nexttrackpressedregistered = false; ///pressed the "rewind" button on the Audio control box, the long press "previous" key async void Mediacontrol_rewi
        Ndpressed (object sender, Object e) {await outputmessage ("Rewind pressed");
        ///Press the "Fast-forward" button on the audio control box, that is, the "Next" key async void Mediacontrol_fastforwardpressed (object sender, Object e)
        {await outputmessage ("Fast Forward pressed");
        }//volume level changes (muted, low, full) async void Mediacontrol_soundlevelchanged (object sender, Object e)
        {await outputmessage ("Sound level Changed"); //Create a music list that needs to be played in the background private async void Btnselectfiles_click (object sender, RoutedevenTargs e) {fileopenpicker openpicker = new Fileopenpicker ();
            Openpicker.viewmode = pickerviewmode.list;
            Openpicker.suggestedstartlocation = pickerlocationid.musiclibrary;
            OpenPicker.FileTypeFilter.Add (". mp3");
            OPENPICKER.FILETYPEFILTER.ADD (". wma");
            ireadonlylist<storagefile> files = await openpicker.pickmultiplefilesasync (); if (Files.
                Count > 0) {await createplaylist (files);
            Await Setcurrentplayingasync (_currentsongindex);
        }//start playing private async void Btnplay_click (object sender, RoutedEventArgs e) {if (mediacontrol.isplaying) {await dispatcher.runasync (Coredispatcherprio Rity.
                Normal, () => {mediaelement.pause ();
                });
  Await Outputmessage ("Play/pause pressed-pause");          else {await dispatcher.runasync (Coredispatcherpriority.normal, () =&G
                T
                {Mediaelement.play ();
                });
            Await Outputmessage ("Play/pause pressed-play"); After opening the file, play the private void mediaelement_mediaopened (object sender, Ro, if required to play)
            Utedeventargs e) {if (mediacontrol.isplaying) {mediaelement.play (); After the current music is played, go to the next private async void Mediaelement_mediaended (object sender, rout Edeventargs e) {if (_currentsongindex < _playlist.count-1) {_curren
    
                tsongindex++;
    
                Await Setcurrentplayingasync (_currentsongindex);
                if (mediacontrol.isplaying) {mediaelement.play ();
       }
            } /////According to the foreground operation, set Mediacontrol isplaying Properties//View more highlights in this column: Http://www.bianceng.cnhttp://www.bianceng.cn/Pr
            ogramming/net/private void Mediaelement_currentstatechanged (object sender, RoutedEventArgs e) { if (mediaelement.currentstate = = mediaelementstate.playing) {mediacontrol.isplaying = True
                ;
            Btnplay.content = "Pause";
                else {mediacontrol.isplaying = false;
            Btnplay.content = "Play";
        }///Create music list Private Async Task createplaylist (ireadonlylist<storagefile> files) {if (_previoustrackpressedregistered) {mediacontrol.previoustrackpressed = M
                ediacontrol_previoustrackpressed;
            _previoustrackpressedregistered = false; } if (_nexttrackpressedregistered) {Mediacontrol.nexttrackpressed-= mediacontrol_nexttrackpressed;
            _nexttrackpressedregistered = false;
            } _playlist.clear ();
    
            _currentsongindex = 0; if (Files. Count > 0) {if (Files.
                    Count > 1) {mediacontrol.nexttrackpressed + = mediacontrol_nexttrackpressed;
                _nexttrackpressedregistered = true; foreach (Storagefile file in files) {Songmodel song = new song
                    Model (file); Await song.
                    Loadmusicpropertiesasync ();
                _playlist.add (song); }}//Specify the music you want to play now private async Task setcurrentplayingasync (int playli
            Stindex) {string errormessage = null;
    
            Irandomaccessstream stream = null; try {stream = await _pLaylist[playlistindex].
                File.openasync (Windows.Storage.FileAccessMode.Read); Await Dispatcher.runasync (Coredispatcherpriority.normal, () => {mediaelement.sets Ource (Stream, _playlist[playlistindex]. 
                File.contenttype);
            });
            catch (Exception e) {errormessage = E.message;
            } if (errormessage!= null) {await outputmessage (errormessage); } mediacontrol.artistname = _playlist[playlistindex].
            Artist; Mediacontrol.trackname = _playlist[playlistindex].
        Title; //Output Information private async Task Outputmessage (String message) {await Dispatcher.run Async (Coredispatcherpriority.normal, () => {lblmsg.text = message + ":" + DateTime.Now.To
            String ("Yyyy-mm-dd hh:mm:ss");
        }); }
    }
}

Ok

SOURCE Download: Http://files.cnblogs.com/webabcd/Windows8.rar