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