绘制控件间的连接线

代码来自 网友 loadres

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程序源码：

 

Imports System.Drawing
Imports System.Drawing.Drawing2D

Public Class Form1Class Form1

    Public Shared Function CreateGraphicsPathByControls()Function CreateGraphicsPathByControls(ByVal SourceControl As Control, ByVal TargetControl As Control) As Drawing2D.GraphicsPath
        Dim iGraphicsPath As New Drawing2D.GraphicsPath

        Dim iSP As Point
        Dim iEP As Point

        If (TargetControl.Left + TargetControl.Width) < SourceControl.Left Then
            '左边
            If (TargetControl.Top + TargetControl.Height) < SourceControl.Top Then
                '左上角
                '|_
                '
                iSP.X = SourceControl.Left
                iSP.Y = SourceControl.Top + SourceControl.Height  4
                iEP.X = TargetControl.Left + TargetControl.Width * 3  4
                iEP.Y = TargetControl.Top + TargetControl.Height

                iGraphicsPath.AddLine(iSP.X, iSP.Y, iEP.X, iSP.Y)
                iGraphicsPath.AddLine(iEP.X, iSP.Y, iEP.X, iEP.Y)

            ElseIf TargetControl.Top > (SourceControl.Top + SourceControl.Height) Then
                '左下角
                ' _
                '|

                iSP.X = SourceControl.Left
                iSP.Y = SourceControl.Top + SourceControl.Height * 3  4
                iEP.X = TargetControl.Left + TargetControl.Width * 3  4
                iEP.Y = TargetControl.Top

                iGraphicsPath.AddLine(iSP.X, iSP.Y, iEP.X, iSP.Y)
                iGraphicsPath.AddLine(iEP.X, iSP.Y, iEP.X, iEP.Y)
            Else
                '左边
                '_
                '
                iSP.X = SourceControl.Left
                iSP.Y = SourceControl.Top + SourceControl.Height  2
                iEP.X = TargetControl.Left + TargetControl.Width
                iEP.Y = TargetControl.Top + TargetControl.Height  2

                iGraphicsPath.AddLine(iSP.X, iSP.Y, iEP.X + (iSP.X - iEP.X)  2, iSP.Y)
                iGraphicsPath.AddLine(iEP.X + (iSP.X - iEP.X)  2, iEP.Y, iEP.X, iEP.Y)
            End If
        ElseIf TargetControl.Left > (SourceControl.Left + TargetControl.Width) Then
            '右边
            If (TargetControl.Top + TargetControl.Height) < SourceControl.Top Then
                '右上角
                '_|
                '
                iSP.X = SourceControl.Left + SourceControl.Width
                iSP.Y = SourceControl.Top + SourceControl.Height  4
                iEP.X = TargetControl.Left + TargetControl.Width  4
                iEP.Y = TargetControl.Top + TargetControl.Height

                iGraphicsPath.AddLine(iSP.X, iSP.Y, iEP.X, iSP.Y)
                iGraphicsPath.AddLine(iEP.X, iSP.Y, iEP.X, iEP.Y)

            ElseIf TargetControl.Top > (SourceControl.Top + SourceControl.Height) Then
                '右下角
                '_
                ' |
                iSP.X = SourceControl.Left + SourceControl.Width
                iSP.Y = SourceControl.Top + SourceControl.Height * 3  4
                iEP.X = TargetControl.Left + TargetControl.Width  4
                iEP.Y = TargetControl.Top

                iGraphicsPath.AddLine(iSP.X, iSP.Y, iEP.X, iSP.Y)
                iGraphicsPath.AddLine(iEP.X, iSP.Y, iEP.X, iEP.Y)

            Else
                '右边
                '_
                '
                iSP.X = SourceControl.Left + SourceControl.Width
                iSP.Y = SourceControl.Top + SourceControl.Height  2
                iEP.X = TargetControl.Left
                iEP.Y = TargetControl.Top + TargetControl.Height  2

                iGraphicsPath.AddLine(iSP.X, iSP.Y, iEP.X + (iSP.X - iEP.X)  2, iSP.Y)
                iGraphicsPath.AddLine(iEP.X + (iSP.X - iEP.X)  2, iEP.Y, iEP.X, iEP.Y)

            End If
        Else
            If (TargetControl.Top + TargetControl.Height) < SourceControl.Top Then
                '上边
                '|
                '
                iSP.X = SourceControl.Left + SourceControl.Width  2
                iSP.Y = SourceControl.Top
                iEP.X = TargetControl.Left + TargetControl.Width  2
                iEP.Y = TargetControl.Top + TargetControl.Height

                iGraphicsPath.AddLine(iSP.X, iSP.Y, iSP.X, iSP.Y - (iSP.Y - iEP.Y)  2)
                iGraphicsPath.AddLine(iEP.X, iSP.Y - (iSP.Y - iEP.Y)  2, iEP.X, iEP.Y)

            ElseIf TargetControl.Top > (SourceControl.Top + SourceControl.Height) Then
                '下边
                '|
                iSP.X = SourceControl.Left + SourceControl.Width  2
                iSP.Y = SourceControl.Top + SourceControl.Height
                iEP.X = TargetControl.Left + TargetControl.Width  2
                iEP.Y = TargetControl.Top

                iGraphicsPath.AddLine(iSP.X, iSP.Y, iSP.X, iSP.Y - (iSP.Y - iEP.Y)  2)
                iGraphicsPath.AddLine(iEP.X, iSP.Y - (iSP.Y - iEP.Y)  2, iEP.X, iEP.Y)
            Else
                '重合
                '什么都不做
            End If
        End If

        Return iGraphicsPath
    End Function


    Private Sub Button1_Click()Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim iG As Graphics = Me.CreateGraphics
        Dim iGP As Drawing2D.GraphicsPath
        Dim iSPen As New Pen(Color.Blue, 3)

        iSPen.StartCap = LineCap.RoundAnchor
        iSPen.EndCap = LineCap.ArrowAnchor

        iGP = CreateGraphicsPathByControls(ListBox1, ListBox2)
        iG.DrawPath(iSPen, iGP)
    End Sub
End Class