vb.net - 音频文件类

Question

我正在使用 VB.net VS2012 并且需要一些帮助来播放音频文件。

这是我的代码：

''' <summary>
''' This class is a wrapper for the Windows API calls to play wave, midi or mp3 files.
''' </summary>
''' <remarks>
''' </remarks>
Public Class AudioFile
'***********************************************************************************************************
'        Class:  PlayFile
'   Written By:  Blake Pell (bpell@indiana.edu)
' Initial Date:  03/31/2007
' Last Updated:  02/04/2009
'***********************************************************************************************************

' Windows API Declarations
Private Declare Function mciSendString Lib "winmm.dll" Alias "mciSendStringA" (ByVal lpstrCommand As String, ByVal lpstrReturnString As String, ByVal uReturnLength As Int32, ByVal hwndCallback As Int32) As Int32

''' <summary>
''' Constructor:  Location is the filename of the media to play.  Wave files and Mp3 files are the supported formats.
''' </summary>
''' <param name="Location"></param>
''' <remarks></remarks>
Public Sub New(ByVal location As String)
    Me.Filename = location
End Sub

''' <summary>
''' Plays the file that is specified as the filename.
''' </summary>
''' <remarks></remarks>
Public Sub Play()

    If _filename = "" Or Filename.Length <= 4 Then Exit Sub

    Select Case Right(Filename, 3).ToLower
        Case "mp3"
            mciSendString("open """ & _filename & """ type mpegvideo alias audiofile", Nothing, 0, IntPtr.Zero)

            Dim playCommand As String = "play audiofile from 0"

            If _wait = True Then playCommand += " wait"

            mciSendString(playCommand, Nothing, 0, IntPtr.Zero)
        Case "wav"
            mciSendString("open """ & _filename & """ type waveaudio alias audiofile", Nothing, 0, IntPtr.Zero)
            mciSendString("play audiofile from 0", Nothing, 0, IntPtr.Zero)
        Case "mid", "idi"
            mciSendString("stop midi", "", 0, 0)
            mciSendString("close midi", "", 0, 0)
            mciSendString("open sequencer!" & _filename & " alias midi", "", 0, 0)
            mciSendString("play midi", "", 0, 0)
        Case Else
            Throw New Exception("File type not supported.")
            Call Close()
    End Select

    IsPaused = False

End Sub

''' <summary>
''' Pause the current play back.
''' </summary>
''' <remarks></remarks>
Public Sub Pause()
    mciSendString("pause audiofile", Nothing, 0, IntPtr.Zero)
    IsPaused = True
End Sub

''' <summary>
''' Resume the current play back if it is currently paused.
''' </summary>
''' <remarks></remarks>
Public Sub [Resume]()
    mciSendString("resume audiofile", Nothing, 0, IntPtr.Zero)
    IsPaused = False
End Sub

''' <summary>
''' Stop the current file if it's playing.
''' </summary>
''' <remarks></remarks>
Public Sub [Stop]()
    mciSendString("stop audiofile", Nothing, 0, IntPtr.Zero)
End Sub

''' <summary>
''' Close the file.
''' </summary>
''' <remarks></remarks>
Public Sub Close()
    mciSendString("close audiofile", Nothing, 0, IntPtr.Zero)
End Sub

Private _wait As Boolean = False
''' <summary>
''' Halt the program until the .wav file is done playing.  Be careful, this will lock the entire program up until the
''' file is done playing.  It behaves as if the Windows Sleep API is called while the file is playing (and maybe it is, I don't
''' actually know, I'm just theorizing).  :P
''' </summary>
''' <value></value>
''' <returns></returns>
''' <remarks></remarks>
Public Property Wait() As Boolean
    Get
        Return _wait
    End Get
    Set(ByVal value As Boolean)
        _wait = value
    End Set
End Property

''' <summary>
''' Sets the audio file's time format via the mciSendString API.
''' </summary>
''' <value></value>
''' <returns></returns>
''' <remarks></remarks>
ReadOnly Property Milleseconds() As Integer
    Get
        Dim buf As String = Space(255)
        mciSendString("set audiofile time format milliseconds", Nothing, 0, IntPtr.Zero)
        mciSendString("status audiofile length", buf, 255, IntPtr.Zero)

        buf = Replace(buf, Chr(0), "") ' Get rid of the nulls, they muck things up

        If buf = "" Then
            Return 0
        Else
            Return CInt(buf)
        End If
    End Get
End Property

''' <summary>
''' Gets the status of the current playback file via the mciSendString API.
''' </summary>
''' <value></value>
''' <returns></returns>
''' <remarks></remarks>
ReadOnly Property Status() As String
    Get
        Dim buf As String = Space(255)
        mciSendString("status audiofile mode", buf, 255, IntPtr.Zero)
        buf = Replace(buf, Chr(0), "")  ' Get rid of the nulls, they muck things up
        Return buf
    End Get
End Property

''' <summary>
''' Gets the file size of the current audio file.
''' </summary>
''' <value></value>
''' <returns></returns>
''' <remarks></remarks>
ReadOnly Property FileSize() As Integer
    Get
        Try
            Return My.Computer.FileSystem.GetFileInfo(_filename).Length
        Catch ex As Exception
            Return 0
        End Try
    End Get
End Property

''' <summary>
''' Gets the channels of the file via the mciSendString API.
''' </summary>
''' <value></value>
''' <returns></returns>
''' <remarks></remarks>
ReadOnly Property Channels() As Integer
    Get
        Dim buf As String = Space(255)
        mciSendString("status audiofile channels", buf, 255, IntPtr.Zero)

        If IsNumeric(buf) = True Then
            Return CInt(buf)
        Else
            Return -1
        End If
    End Get
End Property

''' <summary>
''' Used for debugging purposes.
''' </summary>
''' <value></value>
''' <returns></returns>
''' <remarks></remarks>
ReadOnly Property Debug() As String
    Get
        Dim buf As String = Space(255)
        mciSendString("status audiofile channels", buf, 255, IntPtr.Zero)

        Return Str(buf)
    End Get
End Property

Private _isPaused As Boolean = False
''' <summary>
''' Whether or not the current playback is paused.
''' </summary>
''' <value></value>
''' <returns></returns>
''' <remarks></remarks>
Public Property IsPaused() As Boolean
    Get
        Return _isPaused
    End Get
    Set(ByVal value As Boolean)
        _isPaused = value
    End Set
End Property

Private _filename As String
''' <summary>
''' The current filename of the file that is to be played back.
''' </summary>
''' <value></value>
''' <returns></returns>
''' <remarks></remarks>
Public Property Filename() As String
    Get
        Return _filename
    End Get
    Set(ByVal value As String)

        If My.Computer.FileSystem.FileExists(value) = False Then
            Throw New System.IO.FileNotFoundException
            Exit Property
        End If

        _filename = value
    End Set
End Property
End Class

这段代码运行良好。能否请我帮忙创建一个在音频文件播放完毕时调用的事件。音频文件完成后，“状态”为“已停止”。我如何查看何时发生这种情况并为其创建事件？

Answer 1

似乎没有办法在播放状态更改时注册回调，因此您必须使用观察者（即计时器）。

Private WithEvents StatusMonitor As New Timers.Timer(100)
Private Property LastStatus As String

Private Sub StatusMonitor_Elapsed(sender As Object, e As Timers.ElapsedEventArgs) Handles StatusMonitor.Elapsed
    If Not String.Equals(Me.Status, Me.LastStatus) Then
        Me.LastStatus = Me.Status
        RaiseEvent PlaybackStatusChanged(Me, New PlaybackStatusChangedEventArgs(Me.Status))
    End If
End Sub

Public Event PlaybackStatusChanged(sender As Object, e As PlaybackStatusChangedEventArgs)

Public Class PlaybackStatusChangedEventArgs
    Inherits EventArgs

    Private _status As String

    Public Sub New(status As String)
        _status = status
    End Sub

    Public ReadOnly Property Status As String
        Get
            Return _status
        End Get
    End Property
End Class

它的作用是将状态存储在私有属性中，并每 100 毫秒将其与当前状态进行比较。如果状态已更改，它会触发PlaybackStatusChanged事件以及包含新状态的参数。然后，您可以侦听此事件，并检查e.Status事件回调，就好像您直接从AudioFile.Status.

编辑

在进行了几次测试运行后，我发现 status 属性的行为不一致。由于我似乎无法弄清楚的原因，它似乎也返回了很多空白。无论如何，结果，传递给状态事件的状态是错误的。

Answer 2

我不知道该怎么做。但你能做的就是这个。在您的主窗体上，将像 lol 这样的字符串变暗作为字符串

现在对于一个按钮，设置以下代码：

lol = "Audio file path goes here :3"
    Dim audio As New AudioFile(lol)
    Timer1.Start()
    audio.Play()

添加一个计时器，并将其间隔设置为 10。

对于计时器代码，添加以下内容：

 Dim audio As New AudioFile(lol)
    If audio.Status.Contains("stopped") Then
        audio.Play()
    End If

这样，当歌曲播放完毕后，计时器将自动重新开始播放。它为该变量上的音频文件设置，所以只需让按钮设置该变量上的路径并繁荣。你的一套。

希望有帮助...