VB绘制粗虚线的代码
我们知道，VB在画虚线时，线宽只能为1（DrawWidth=1），但有时候我们必须要画粗虚线，那该怎么办呢？解决这个问题的思路是：要画多宽的虚线，只要在最初那条虚线的两旁画相应数量的虚线就行了。比方说，画5个像素宽的虚线，那么就在第一根虚线的两旁再各画2根同样长的虚线即可。笔者据此编写了一段代码，与各位共享。新建一个窗体，上面只放置一个Line控件。代码如下：
Option Explicit
Dim BjDash As Boolean '是否画虚线：0-画实线，1-画虚线
Dim drawW As Integer '画虚线时原先的线宽暂存
Dim editX As Integer '鼠标初始X坐标
Dim editY As Integer '鼠标初始Y坐标
Private Sub Form_Load()
AutoRedraw = True
ScaleMode = 3
DrawWidth = 5
Line1.BorderWidth = DrawWidth
Line1.Visible = False
End Sub
Private Sub Form_KeyDown(KeyCode As Integer, Shift As Integer)
If Shift = 2 Then '按【Ctrl】键单次画虚线，双次复原
BjDash = Not BjDash
If BjDash Then
drawW = DrawWidth
DrawWidth = 1
DrawStyle = 1
Else
DrawWidth = drawW
Line1.BorderWidth = DrawWidth
DrawStyle = 0
End If
End If
End Sub
Private Sub Form_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)
editX = X: editY = Y
Line1.X1 = X: Line1.Y1 = Y: Line1.Visible = True
End Sub
Private Sub Form_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
Line1.X2 = X: Line1.Y2 = Y
End Sub
Private Sub Form_MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single)
Dim p As Integer, i As Integer, j As Integer
Line1.Visible = False
If BjDash Then '如果画虚线
p = Atn((editY - Y) / (0.00001 + editX - X)) * 180 / 3.14159 '求虚线与水平线的夹角
If p < 0 Then p = 180 + p
For i = 0 To drawW - 1
If p < 45 Or p > 135 Then
Line (editX, editY + j)-(X, Y + j), 0
Else
Line (editX + j, editY)-(X + j, Y), 0
End If
If i Mod 2 = 0 Then j = Abs(j) + 1 Else j = -j
Next
Else
Line (editX, editY)-(X, Y), 0
End If
End Sub
简要说明：
操作时先设置好虚线宽（DrawWidth属性值），再按一下【Ctrl】键，表示要画虚线了，然后按下鼠标左键不放，在窗体上拖动，这时画的是实线，但只要鼠标一松，就变成了虚线。如果再次按下【Ctrl】键，就复原了原设置，后续操作只画实线不画虚线。
Form_MouseUp过程中有一行求虚线与水平线夹角的代码，当夹角在45°—135°之间时，当作竖线，那么增加的虚线画在初始线的左右两旁，否则当作横线，增加的虚线画在初始线的上下两边。
本代码如果与笔者发表的《VB绘制带箭头直线的代码》结合起来，就能绘制带箭头的虚线。
