从图像列表加载和查看图像

正如您所看到的，下面给出的代码不是很有用。是否可以缩短代码。鼠标滚轮向后和向前给出相同的结果（下图）。无法配置 Keydown。

Private Sub Images_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
    count += 1
    If count + 1 > ImageList1.Images.Count Then
        count = 0
    End If
    PictureBox1.Image = ImageList1.Images.Item(count)
End Sub

Private Sub Images_MouseWheel(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles MyBase.MouseWheel
    count += 1
    If count + 1 > ImageList1.Images.Count Then
        count = 0
    End If
    PictureBox1.Image = ImageList1.Images.Item(count)
End Sub

Private Sub Images_KeyDown(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles MyBase.KeyDown
    If e.KeyCode = Keys.Down Then
        count += 1
        If count + 1 > ImageList1.Images.Count Then
            count = 0
        End If
        PictureBox1.Image = ImageList1.Images.Item(count)
    End If
End Sub

这是一种缩短它的方法，只需使用函数即可：

Private Sub Images_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
    PictureBox1.Image = ImageList1.Images.Item(increaseCount(count))
End Sub

Private Sub Images_MouseWheel(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles MyBase.MouseWheel
If e.Delta > 0 Then
    PictureBox1.Image = ImageList1.Images.Item(decreaseCount(count))
ElseIf e.Delta < 0 Then
    PictureBox1.Image = ImageList1.Images.Item(increaseCount(count))
End If
End Sub

Private Sub Images_KeyDown(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles MyBase.KeyDown
If e.KeyCode = Keys.Down Then
   PictureBox1.Image = ImageList1.Images.Item(increaseCount(count))
End If
End Sub

Private Function increaseCount(ByRef count as integer) As Integer
    count += 1
    If count + 1 > ImageList1.Images.Count Then
        count = 0
    End If
    Return count
End Sub

Private Function decreaseCount(ByRef count as integer) As Integer
    count -= 1
    If count - 1 > ImageList1.Images.Count OR count < 0 Then
        count = 0
    End If
    Return count
End Sub

e.Delta 是您滚动的距离，这取决于控制面板中有关鼠标滚轮滚动的选项。因此，我们无法确定这些值是什么，但好处是向上滚动始终为正，向下滚动始终为负。