Windows Phone实用开发技巧（37）：创建一个全局播放器

在做windows phone 开发的时候，有时候我们需要在某些页面中进行声音的播放。而播放的方式也有多种：

1. 使用MediaElement

2. 使用SoundEffect

3. 使用后台播放

SoundEffect只能播放wav格式的文件；后台播放可以在程序退出后仍然继续播放；MediaElement适用于大多数情况，但不能实现后台播放，MediaElement依赖页面并且在页面中只有一个实例可以正常工作。

本文讲讲如何在应用中使用MediaElement作为程序全局播放器，并提供一个帮助类。

由于MediaElement依赖于UI，我们不能在ViewModel中创建一个MediaElement实例进行声音的播放，所以我们需要将MediaElement放置在一个UI容器中,下面是帮助类的代码：

public class GlobalPlayer
{
static Popup popUp;
private static MediaElement _player;

public static void Play(string filePath)
{
popUp = new Popup();
_player = new MediaElement();
_player.Source = null;
popUp.Child = _player;
popUp.IsOpen = true;
try
{
using (var store = IsolatedStorageFile.GetUserStoreForApplication())
{
using (var stream = new IsolatedStorageFileStream(filePath, FileMode.Open, store))
{
_player.SetSource(stream);
_player.Volume = 1.0;
_player.Play();
_player.MediaEnded += new RoutedEventHandler((sender, e) =>
{
stream.Close();
stream.Dispose();
_player.Source = null;
_player = null;

});
_player.MediaFailed += new EventHandler<ExceptionRoutedEventArgs>((s, args) =>
{
stream.Close();
stream.Dispose();
_player.Source = null;
_player = null;
});
}
}
}
catch (Exception)
{
_player.Source = null;
_player = null;

}
}

public static void StopPlay()
{
if (_player != null && _player.CurrentState == MediaElementState.Playing)
{
try
{
_player.Source = null;
_player.Stop();
}
catch (Exception)
{
//throw;
}
}
}
}

使用方法十分简单，当我们需要在不同的页面播放同一声音的时候，将存储在独立空间的路径传入即可。

Updated 2013-02-28: 我们使用静态构造函数去初始化MediaElement 和PopUp

static Player() { popUp = new Popup(); _player = new MediaElement(); popUp.Child = _player; popUp.IsOpen = true; }

public static void Play(string filePath)

{ _player.Source = null; try { using (var store = IsolatedStorageFile.GetUserStoreForApplication()) { using (var stream = new IsolatedStorageFileStream(filePath, FileMode.Open, store)) { _player.SetSource(stream); _player.Volume = 1.0; _player.Play(); _player.MediaEnded += new RoutedEventHandler((sender, e) => { stream.Close(); stream.Dispose(); _player.Source = null; _player = null; }); _player.MediaFailed += new EventHandler<ExceptionRoutedEventArgs>((s, args) => { stream.Close(); stream.Dispose(); _player.Source = null; _player = null; }); } } } catch (Exception) { _player.Source = null; _player = null; } }