如何在VB.NET中处理KeyDown

Question

好的，这是我的难题。 这是我的代码：

   If e.KeyCode = Keys.A Then
        TextBox1.AppendText("C, ")
        PictureBox2.Visible = True
        My.Computer.Audio.Play(My.Resources.C, AudioPlayMode.Background)
   End If

现在，当我在Form1_KeyDown下输入此命令时，Visual Basic会这样认为：

'KeyCode不是'System.EventArgs'的成员

现在我已经看过此代码的工作原理，但现在不在这里。 有什么帮助吗？

这是完整的代码：

Private Sub Form1_KeyDown(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs)
    If e.KeyCode = Keys.A Then
        TextBox1.AppendText("A, ")
        PictureBox2.Visible = True
        My.Computer.Audio.Play(My.Resources.C, AudioPlayMode.Background)
    End If
    If e.KeyCode = Keys.S Then
        TextBox1.AppendText("C,")
        PictureBox14.Visible = True
        My.Computer.Audio.Play(My.Resources.D, AudioPlayMode.Background)
    End If
End Sub

Answer 1

不知道为什么您的方法定义将e声明为EventArgs ，但解决方法只是使参数成为KeyEventArgs类型。 这是因为EventArgs （自然）不包含称为KeyCode的属性，而KeyEventArgs包含！

将事件处理程序方法定义更改为以下内容：

Private Sub foo_KeyDown(sender As Object, e As KeyEventArgs)
    If e.KeyCode = Keys.A Then
        TextBox1.AppendText("A, ")
        PictureBox2.Visible = True
        My.Computer.Audio.Play(My.Resources.C, AudioPlayMode.Background)
    ElseIf e.KeyCode = Keys.S Then
        TextBox1.AppendText("C,")
        PictureBox14.Visible = True
        My.Computer.Audio.Play(My.Resources.D, AudioPlayMode.Background)
    End If
End Sub

Answer 2

听起来您的方法使用了错误的EventArgs。 Control.KeyDown事件将其作为System.Windows.Forms.KeyEventArgs发送。 所以你的代码应该读为

Private Sub Form1_KeyDown(sender As Object, e As System.Windows.Forms.KeyEventArgs)
   // code here
End Sub

Answer 3

我发现有时候您需要提供类似于以下内容的完整对象类型：

Private Sub Form1_KeyDown(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles Me.KeyDown
MsgBox(e.KeyCode.ToString()) 'Message what the keycode
If (e.KeyCode = Keys.A) Then
    MsgBox("e.KeyCode = Keys.A") 'Message that I've found the A
    TextBox1.AppendText("C, ")
    PictureBox2.Visible = True
    My.Computer.Audio.Play(My.Resources.C, AudioPlayMode.Background)
End If

结束子

您是否也尝试过在类似于以下形式的文本框中测试此内容（示例中的文本框名为TextBoxKeyTest）？

    Private Sub TextBoxKeyTest_KeyDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles TextBoxKeyTest.KeyDown
    MsgBox(e.KeyCode.ToString())'Message what the keycode
    If (e.KeyCode = Keys.A) Then
        MsgBox("e.KeyCode = Keys.A")'Message that I've found the A
        TextBox1.AppendText("C, ")
        PictureBox2.Visible = True
        My.Computer.Audio.Play(My.Resources.C, AudioPlayMode.Background)
    End If
End Sub

Answer 4

这应该在VB 2010中起作用

Private Sub cmdWiden_KeyUp(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles Me.KeyUp
        If e.KeyCode = Keys.Up Then Me.Top = Me.Top - 5
        If e.KeyCode = Keys.Down Then Me.Top = Me.Top + 5
        If e.KeyCode = Keys.Left Then Me.Left = Me.Left - 5
        If e.KeyCode = Keys.Right Then Me.Left = Me.Left + 5
End Sub