vb.net - VB.NET 从列表中沿 X 坐标移动直线的所有点

Question

我有一个函数，可以从函数中的点列表中画线VB.NET到PictureBox. 将两个点添加到列表中，并在列表中添加的所有点之间绘制一条线。但是，当将新点添加到列表中时，我希望将所有先前绘制的线移到左侧。

例如，如果分别从列表中(9, 0) (9, 4)和之间绘制了两条不同的线(10, 0) (10, 3)，并将第三行添加到列表中(10, 0) (10, 2)，我想像这样移动前两行：

(9, 0), (9, 4)到(8, 0), (8, 4)

(10, 0), (10, 3)到(9, 0), (9, 3)

这是我的意思的演示。

绿线是绘制的第一条线，黄色是绘制的第二条线。在第二个图中，添加了一条深蓝色的线，并且绘制的前两条线，黄色和绿色，都向左移动。

我正在使用此代码来尝试绘制这些类型的线条。

Public Class Line

    Public ReadOnly Property StartPoint As Point

    Public ReadOnly Property EndPoint As Point

    Public Sub New(startPoint As Point, endPoint As Point)
        Me.StartPoint = startPoint
        Me.EndPoint = endPoint
    End Sub

End Class

Public Class Form1
Private lines As New List(Of Line)

Private Sub PictureBox1_Paint(sender As Object, e As PaintEventArgs) Handles PictureBox1.Paint
    For Each line In lines
        e.Graphics.DrawLine(Pens.Black, line.StartPoint, line.EndPoint)
    Next
End Sub

Private Sub AddNewLine(length As Integer)

    Dim pictureBoxRightXPoint As Integer = 300 'the right most side of the PictureBox is the x coordinate of 300 (PictureBox has the x size of 300).

    For Each l As line In lines 'move all points of X in all previously drawn lines in the list to the left.
            l.StartPoint.X = l.StartPoint.X - 1
            l.EndPoint.X = l.EndPoint.X - 1

    Next
    lines.Add(New Line((pictureBoxRightXPoint, 0), (pictureBoxRightXPoint, length))
    PictureBox1.Invalidate() 'Refresh the PictureBox to redraw the lines.
End Sub

End Class

添加后，我收到以下错误：

表达式是一个值，因此不能作为赋值的目标

当我尝试1从 X 坐标中减去以将列表中已经存在的所有点向左移动时。

PictureBox将所有先前绘制的点向左移动时，如何解决此问题或在 a 中绘制一条线？（注意：列表中可能已经添加了多行）。

（仅在列表中绘制和添加行的代码来自：https ://stackoverflow.com/a/66621165/14924603 ）。

标签： vb.netlistlinegdi+

Answer 1

如果您想绘制我相信PictureBox您PictureBox在. 要将所有先前绘制的图形移到左侧，您可以将' 位置的位置移动到左侧。PanelPictureBoxPictureBoxPanel

您可以使用之前的函数添加新行，但将您的PictureBox并将其开头移动到Panel. 要添加新行，请使用以下命令：

Dim xint As Integer = 1

Dim r As Random = New Random
xint = xint + 1
Dim Point1 As New Point(xint, r.Next(40, 79))
Dim point2 As New Point(xint, r.Next(80, 100))

AddNewLine(Point1, point2)
PictureBox1.Left -= 1 'Move the PictureBox Left

PictureBox1.Size = New Size(PictureBox2.Size.Width + 1, 269) 'Change its size to allow for continuous line drawing 

Y您可以将我使用的随机长度替换为您操作的实际点。您链接的画线功能可以正常工作。为了澄清，请确保使用此：

Private Sub AddNewLine(startPoint As Point, endPoint As Point)
    lines.Add(New Line(startPoint, endPoint))
    PictureBox1.Invalidate()
End Sub

你的Paint活动应该是这样的：

For Each line In lines
     e.Graphics.DrawLine(Pens.Black, line.StartPoint, line.EndPoint)
Next