vb.net - 使用面板的 Autoscroll = True 在图片框中进行矩形选择以裁剪图像时自动移动滚动条

Question

我在面板顶部有一个图片框。我有一个矩形选区，可用于选择图像的一部分进行裁剪。由于我已将面板的自动滚动属性设置为 True，并且图像在图片框很大，我有滚动条。但是为了选择图像的一部分进行裁剪，我需要将矩形拖到我看不到的范围之外。当鼠标到达图片框的最右边时，我不能这样做。我想以一种方式设计它，当鼠标到达最右边时，我的滚动条应该自动向右移动。但是使用 Autoscroll 属性我无法获得滚动条值。任何解决方法可用于此问题？

Answer 1

使用 Timer 来移动 AutoScrollPosition 属性可能会更流畅一些:

Private horzMove As ArrowDirection = -1
Private vertMove As ArrowDirection = -1

Private Sub PictureBox1_MouseMove(sender As Object, e As MouseEventArgs) Handles PictureBox1.MouseMove
  If e.Button = MouseButtons.Left Then
    If Panel1.AutoScrollPosition.X + e.Location.X > Panel1.ClientSize.Width Then
      horzMove = ArrowDirection.Right
    ElseIf Panel1.AutoScrollPosition.X + e.Location.X < 0 Then
      horzMove = ArrowDirection.Left
    Else
      horzMove = -1
    End If
    If Panel1.AutoScrollPosition.Y + e.Location.Y > Panel1.ClientSize.Height Then
      vertMove = ArrowDirection.Down
    ElseIf Panel1.AutoScrollPosition.Y + e.Location.Y < 0 Then
      vertMove = ArrowDirection.Up
    Else
      vertMove = -1
    End If
  End If
End Sub

Private Sub PictureBox1_MouseUp(sender As Object, e As MouseEventArgs) Handles PictureBox1.MouseUp
  horzMove = -1
  vertMove = -1
End Sub

确保计时器已启用:

Private Sub Timer1_Tick(sender As Object, e As EventArgs) Handles Timer1.Tick
  If horzMove > -1 Or vertMove > -1 Then
    Dim newLeft As Integer = -Panel1.AutoScrollPosition.X
    Dim newTop As Integer = -Panel1.AutoScrollPosition.Y
    Select Case horzMove
      Case ArrowDirection.Left
        newLeft = -Panel1.AutoScrollPosition.X - 32
      Case ArrowDirection.Right
        newLeft = -Panel1.AutoScrollPosition.X + 32
    End Select
    Select Case vertMove
      Case ArrowDirection.Down
        newTop = -Panel1.AutoScrollPosition.Y + 32
      Case ArrowDirection.Up
        newTop = -Panel1.AutoScrollPosition.Y - 32
    End Select
    Panel1.AutoScrollPosition = New Point(newLeft, newTop)
  End If
End Sub