Windows phone 墓碑机制的一些源码

让我们创建一个空wp7项目，要实现这个场景，首先我们将在mainpage.xaml中添加MediaElement来播放音频流。

<MediaElement Name="mediaElement" BufferingTime="0:0:5" AutoPlay="True" Margin="419,1,1,611" />

添加一个滚动条 一个开始一个暂停  一个剩余时间

<Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0" >
            <MediaElement Name="mediaElement" BufferingTime="0:0:5" AutoPlay="True" Margin="419,1,1,611" />
            <ProgressBar IsHitTestVisible="True" IsIndeterminate="True" Height="3" HorizontalAlignment="Right" Margin="0,235,0,0" Name="progressBarAPlayerPage" VerticalAlignment="Top" Width="460" />
            <TextBlock Height="30" HorizontalAlignment="Center" TextAlignment="Center" Margin="0,199,0,0" Name="progressBarTextAPlayerPage" Text="loading" Foreground="White" VerticalAlignment="Top" Width="444" />
              <ProgressBar Height="60" Name="progressBar" Margin="12,256,6,337" />
             <Button Content="play"  Visibility="Collapsed"   Height="72" HorizontalAlignment="Left" Margin="12,353,0,0" Name="play_btn" VerticalAlignment="Top" Width="438" Click="play_btn_Click" />
            <Button Content="pause" Visibility="Collapsed"  Height="72" HorizontalAlignment="Left"  Margin="12,353,0,0" Name="pause_btn" VerticalAlignment="Top" Width="438" Click="pause_btn_Click" />
            <TextBlock Height="58" Foreground="White" HorizontalAlignment="Left" Margin="226,146,0,0" Name="songTime" Text=""  TextAlignment="Center" VerticalAlignment="Top" Width="224" Style="{StaticResource PhoneTextTitle1Style}" FontFamily="Segoe WP SemiLight" FontSize="42" />
            <TextBlock Height="58" HorizontalAlignment="Left" Margin="12,146,0,0" Name="textBlock1" Text="Track Time :" VerticalAlignment="Top" Width="208"  Style="{StaticResource PhoneTextTitle1Style}" FontFamily="Segoe WP SemiLight" FontSize="42" />
</Grid>

播放音乐

   void playSong()

        {

            play_btn.Opacity = 0.5;

           pause_btn.Opacity = 0.5;

            play_btn.IsHitTestVisible = false;

            pause_btn.IsHitTestVisible = false;

            songTime.Text = "00.00";



            mediaElement.MediaOpened += new RoutedEventHandler(mediaElement_MediaOpened);

            mediaElement.MediaEnded += new RoutedEventHandler(mediaElement_MediaEnded);

            mediaElement.CurrentStateChanged += new RoutedEventHandler(mediaElement_CurrentStateChanged);

            currentPosition.Tick += new EventHandler(currentPosition_Tick);

           //enter url : http://www.yourdomain.com/audio.mp3 

            mediaElement.Source =new Uri( "REPLACE_THIS_WITH_REMOTE_MP3",UriKind.RelativeOrAbsolute);   
       }//end of funt

播放跟暂停

private void play_btn_Click(object sender, RoutedEventArgs e)

       {

           mediaElement.Play();

       }



private void pause_btn_Click(object sender, RoutedEventArgs e)

        {

            mediaElement.Pause();

        }//end of funt

现在当用户按下设备上的Windows键，OnNavigatedFrom()方法被调用，在这里我们获取当前MediaElement音轨位置。

protected override void OnNavigatedFrom(System.Windows.Navigation.NavigationEventArgs e)
        {
            base.OnNavigatedFrom(e);
            thisApp.iCurrentTrackPositionText = mediaElement.Position.TotalMinutes.ToString();
            mediaElement.Stop();
        }//end of funt

最后在我们处理Application_Deactivated()事件保存当前音轨信息到IsolatedStorage。

private void Application_Deactivated(object sender, DeactivatedEventArgs e)
        {
            SaveCurrentTrackPosition(); 
        }

void SaveCurrentTrackPosition()
        {

            //read file
            //Obtain a virtual store for application
            IsolatedStorageFile fileStorage = IsolatedStorageFile.GetUserStoreForApplication();
            //Create a new StreamReader
            StreamReader fileReader = null;
            try
            {
                //Read the file from the specified location.
                fileReader = new StreamReader(new IsolatedStorageFileStream("CurrentTrackPosition.txt", FileMode.Open, fileStorage));
                //Read the contents of the file (the only line we created).
                textFile = fileReader.ReadToEnd();
                fileReader.Close();
            }
            catch
            {
                // MessageBox.Show("error saving data");
            }

            //replace text
            textFile = textFile.Replace(textFile, iCurrentTrackPositionText);
            //write file
            //Obtain a virtual store for application
            IsolatedStorageFile fileStorageUpdate = IsolatedStorageFile.GetUserStoreForApplication();

            //Create a new StreamWriter, to write the file to the specified location.
            StreamWriter fileWriter = new StreamWriter(new IsolatedStorageFileStream("CurrentTrackPosition.txt", FileMode.OpenOrCreate, fileStorageUpdate));
            fileWriter.Write(textFile);
            //Close the StreamWriter.
            fileWriter.Close();
        }

这将使应用程序进入休眠/墓碑状态。现在当用户按下设备back按钮，会调用OnNavigatedTo()方法的Application_Activated()事件。

protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
        {
            base.OnNavigatedTo(e);
            ReadCurrentTrackLastPosition();
            CurrentTrackLastKnowPosition = Convert.ToDouble(textFile);
            initializeSection();
        }

在这里ReadCurrentTrackLastPosition()函数从IsolatedStorage读取当前音轨关于流音频的信息。

void ReadCurrentTrackLastPosition()
        {
            //read file
            //Obtain a virtual store for application
            IsolatedStorageFile fileStorage = IsolatedStorageFile.GetUserStoreForApplication();
            //Create a new StreamReader
            StreamReader fileReader = null;
            try
            {
                //Read the file from the specified location.
                fileReader = new StreamReader(new IsolatedStorageFileStream("CurrentTrackPosition.txt", FileMode.Open, fileStorage));
                //Read the contents of the file (the only line we created).
                textFile = fileReader.ReadToEnd();
                fileReader.Close();
            }
            catch
            {
                 MessageBox.Show("error loading data");
            }

        }

initializeSection()方法从上次它退出位置打开流音频。

private void initializeSection()
        {
            progressBarTextAPlayerPage.Text = "loading";
            progressBarAPlayerPage.IsHitTestVisible = true;
            progressBarAPlayerPage.IsIndeterminate = true;
            progressBarAPlayerPage.Visibility = Visibility.Visible;


            progressBar.Visibility = Visibility.Collapsed;
            play_btn.Visibility = Visibility.Collapsed;
            pause_btn.Visibility = Visibility.Collapsed;
            songTime.Visibility = Visibility.Collapsed;

            string enternetConectivity = Microsoft.Phone.Net.NetworkInformation.NetworkInterface.NetworkInterfaceType.ToString();

            if (enternetConectivity != "None")
            {

                playSong();

            }
            else
            {
               //MessageBox.Show("No internet connection");
            }
        }//end of funt