前言:去年就已经把开发WindowsPhone应用的所有软硬件环境都置备齐全了(脑子一热把原来的MOTO安卓机换成了520,装Windows8 装vs2012...费了好大的力气啊),但是由于种种原因,一直没有时间学习WindowsPhone开发的相关内容。正好凑清明节学校放假,同学们都组团出去欢乐谷游玩了,我没有出去,所以就留下来正好可以安稳的学习一下wp了。
废话不多说,进入正题。
年前做过一个播放音频的小demo,但是不可以后台播放,所以这次我就想弄明白到底怎样可以后台播放。去百度了好久都没有找到相关的内容(ps:可能是我数据挖掘学的不咋地)所以就去MSDN搜索相关问题,没想到还真有后台播放音频的讲解。所以就依葫芦画瓢的做了下来,没想到还真成了。下面我把实现步骤写到下面供大家参考学习。希望能帮到大家!
第一步:新建WindowsPhone项目,我这里命名为”音乐播放器“,然后在解决方案管管理器中右键解决方案名称->添加->新建项目->Windows Phone音频播放代理->给项目命名(这里我命名为MyPlaybackAgent)->确定。在项目名”音乐播放器“中右键->添加->新建文件夹->命名为Audio,然后右键Audio文件夹->添加->现有项->导入几首mp3格式的音乐。然后全选导入的音乐文件右键->属性->复制到输出目录选择”如果较新则复制“,保存项目。Ok ,到这一步大体框架已经完成。结构如下:
第二步:设计MainPage。
具体步骤不在多说,看下图:
xaml代码:
<Grid x:Name="ContentPanel" Grid.Row="1" Margin="0,0,24,0">
<Button Content="上一首" x:Name="btnPrev" HorizontalAlignment="Left" Margin="23,144,0,0" VerticalAlignment="Top" Click="btnPrev_Click"/>
<Button Content="播放" x:Name="btnPlay" HorizontalAlignment="Left" Margin="173,144,0,0" VerticalAlignment="Top" Click="btnPlay_Click"/>
<Button Content="下一首" x:Name="btnNext" HorizontalAlignment="Left" Margin="326,144,0,0" VerticalAlignment="Top" Click="btnNext_Click_1"/>
<TextBlock HorizontalAlignment="Left" x:Name="txtCurrentTrack" Margin="46,257,0,0" TextWrapping="Wrap" Text="当前播放" VerticalAlignment="Top" Height="42" Width="322"/>
</Grid>
第三步:编码
1.在解决方案管理器,右键选择MainPage.xaml->查看代码。
2.引入以下命名空间
using Microsoft.Phone.BackgroundAudio;
3.编辑三个按钮的Click事件,代码如下:
#region 播放控制
private void btnNext_Click_1(object sender, RoutedEventArgs e)
{
BackgroundAudioPlayer.Instance.SkipNext();
}
private void btnPrev_Click(object sender, RoutedEventArgs e)
{
BackgroundAudioPlayer.Instance.SkipPrevious();
}
private void btnPlay_Click(object sender, RoutedEventArgs e)
{
if (BackgroundAudioPlayer.Instance.PlayerState!=PlayState.Playing&&BackgroundAudioPlayer.Instance.Track!=null)
{
BackgroundAudioPlayer.Instance.Play();
}
else
{
BackgroundAudioPlayer.Instance.Stop();
}
}
#endregion
4.在MainPage的构造函数里面加入以下代码:
BackgroundAudioPlayer.Instance.PlayStateChanged += new EventHandler(Instance_PlayStateChanged);
5.Instance_PlayStateChanged方法的代码如下:
void Instance_PlayStateChanged(object sender, EventArgs e)
{
switch (BackgroundAudioPlayer.Instance.PlayerState)
{
case PlayState.Playing:
btnPlay.Content = "暂停";
break;
case PlayState.Paused:
case PlayState.Stopped:
btnPlay.Content = "播放";
break;
}
if (BackgroundAudioPlayer.Instance.Track!=null)
{
txtCurrentTract.Text = BackgroundAudioPlayer.Instance.Track.Title + "By" + BackgroundAudioPlayer.Instance.Track.Artist;
}
}
6.因为这个应用要实现后台播放,也就是当用户按了手机的Back或者Home/Search按键退出程序后再次回到页面后要恢复页面状态,所以有必要重写页面的OnNavigatedTo事件,实现方法如下(此段代码添加到MainPage的类中):
/// <summary>
/// 重写页面返回
/// </summary>
/// <param name="e"></param>
protected override void OnNavigatedTo(NavigationEventArgs e)
{
//如果重新回到页面后播放状态为正在播放,则把播放按钮的Content属性改为“暂停”
if (BackgroundAudioPlayer.Instance.PlayerState==PlayState.Playing)
{
btnPlay.Content = "暂停";
txtCurrentTract.Text = BackgroundAudioPlayer.Instance.Track.Title + "by" + BackgroundAudioPlayer.Instance.Track.Artist;
}
else
{
btnPlay.Content = "播放";
txtCurrentTract.Text = "当前无播放歌曲";
}
base.OnNavigatedTo(e);
}
7.在解决方案管理器中找到App.xaml并右键查看代码,引用以下命名空间:
using System.IO.IsolatedStorage;
using System.Windows.Resources;
8.由于BackgrounAudioPlayer只能播放应用独立存储区(isolated storage)或者网络上的音乐资源(Remote URL),所以有必要用下面的方法来把audio文件夹内的文件拷贝到独立存储区来满足播放要求。(一定要确保下面方法中数组中文件的名字和Audio文件夹内的完全一致,不然会出现空引用的异常):
private void CopyToIsolatedStorage()
{
using (IsolatedStorageFile storage=IsolatedStorageFile.GetUserStoreForApplication())
{
string[] files = new string[] {"Celine Dion - My Heart Will Go On.mp3",
"Conway Twitty - Don't Cry Joni.mp3",
"Gala - Young For You.mp3",
"god is a girl.mp3"
};
foreach (var _fileName in files)
{
if (!storage.FileExists(_fileName))
{
string _filePath = "Audio/" + _fileName;
StreamResourceInfo resource = Application.GetResourceStream(new Uri(_filePath, UriKind.Relative));
using (IsolatedStorageFileStream file=storage.CreateFile(_fileName))
{
int chunkSize = 4096;//4M
byte[] bytes = new byte[chunkSize];
int byteCount;
//每次读4M
while ((byteCount=resource.Stream.Read(bytes,0,chunkSize))>0)
{
file.Write(bytes, 0, byteCount);
}
}
}
}
}
}
9.在App.xaml页的构造函数中调用CopyToIsolatedStorage方法:
CopyToIsolatedStorage();
10.因为音频代理是应用的一部分,当应用处于后台时也会继续运行。所以接下来要为项目”音乐播放器“引入代理,方法如下:
在解决方案资源管理器中右键”音乐播放器“项目中的”引用“->添加引用->解决方案->MyAudioPlaybackAgent->确定。如下图:
-----------------------------------------------------------以下是对AudioPlayer.cs文件进行的操作----------------------------------------
11.打开解决方案资源管理器中音频代理项目中的AudioPlayer.cs文件,在代码中添加以下命名空间的引用:
using System.Collections.Generic;
12.在AudioPlayer.cs文件中声明一个静态的int型的变量用来代表当前播放曲目的个数:
static int currentTrackNumber = 0;//初始为零
13.定义一个Track类型的数组,用来保存播放列表(这里定义成静态的是非常有必要的,这样就不用每次调用音频代理时都重新初始化它,节省资源):
private static List<AudioTrack> _playList = new List<AudioTrack>
{
new AudioTrack(new Uri("Celine Dion - My Heart Will Go On.mp3", UriKind.Relative),
"Celine Dion",
"",
"",
null),
new AudioTrack(new Uri("Conway Twitty - Don't Cry Joni.mp3", UriKind.Relative),
"Conway Twitty",
"",
"",
null),
new AudioTrack(new Uri("Gala - Young For You.mp3", UriKind.Relative),
"Gala",
"",
"",
null),
new AudioTrack(new Uri("god is a girl.mp3", UriKind.Relative),
"Star",
"",
"",
null),
// 一首网络歌曲(设备需联网)
new AudioTrack(new Uri("http://traffic.libsyn.com/wpradio/WPRadio_29.mp3", UriKind.Absolute),
"Episode 29",
"Windows Phone Radio",
"Windows Phone Radio Podcast",
null)
};
14.添加一下代码用来响应用户的操作(播放,上一首,下一首):
private void PlayNextTrack(BackgroundAudioPlayer player)
{
if (++currentTrackNumber >= _playList.Count)
{
currentTrackNumber = 0;
}
PlayTrack(player);
}
private void PlayPreviousTrack(BackgroundAudioPlayer player)
{
if (--currentTrackNumber < 0)
{
currentTrackNumber = _playList.Count - 1;
}
PlayTrack(player);
}
private void PlayTrack(BackgroundAudioPlayer player)
{
if ((player.Track == null) || (player.Track.Title != _playList[currentTrackNumber].Title))
{
player.Track = _playList[currentTrackNumber];
}
if ((player.Track != null) && (player.PlayerState != PlayState.Playing))
{
player.Play();
}
}
15.在OnPlayStateChanged事件中添加以下代码(添加在NotifyComplete之前):
switch (playState)
{
case PlayState.TrackEnded:
PlayNextTrack(player);
break;
// Handle other PlayState changes here
}
16.在OnUserAction 方法中添加以下代码(添加在NotifyComplete之前):
switch (playState)
{
case PlayState.TrackEnded:
PlayNextTrack(player);
break;
// Handle other PlayState changes here
}
17.在OnUserAction 方法中添加以下代码(添加在NotifyComplete之前):
switch (action)
{
case UserAction.Play:
PlayTrack(player);
break;
case UserAction.Pause:
player.Pause();
break;
case UserAction.SkipPrevious:
PlayPreviousTrack(player);
break;
case UserAction.SkipNext:
PlayNextTrack(player);
break;
}
18.Ok,到此为止所有的工作都已经完成,剩下的就是测试你的应用了,以下是我的测试截图:
好啦,到此及本上就完成了一个最简单的音乐播放器.自己可以发挥想象,加入自己的灵感,让应用更灵活,做一个自己的音乐播放器.