VB中画直线问题？

Question

我在picture2控件中画直线，单击起点并按住拖动鼠标时到终点松开可画出一条直线，双击起点第二下不松开并拖动鼠标时会画同以起点开始的N多条直线，请问该如何改，见程序
Private Sub Picture2_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)
If Button <> 1 Then Exit Sub
Picture2.AutoRedraw = False
startx = X '记住起始点
starty = Y
End Sub

Private Sub Picture2_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
If Button <> 1 Then Exit Sub
Picture2.Refresh
Picture2.Line (startx, starty)-(X, Y) '显示橡皮筋效果
End Sub

Private Sub Picture2_MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single)
If Button <> 1 Then Exit Sub
endx = X '记住终止点
endy = Y
Picture2.AutoRedraw = True
Picture2.Line (startx, starty)-(endx, endy) '最终画线
End Sub

Answer 1

“双击起点第二下不松开并拖动鼠标时会画同以起点开始的N多条直线”，这是程序的响应事件问题，第一次MouseDown、MouseUp，再按下时，就产生DblClick事件，同时阻断MouseDown事件，再松开时，就产生MouseUp事件。（需要按同一个键）
DblClick事件只需要MouseDown、MouseUp、MouseDown就会产生。
可以这么说，DblClick事件替换掉了第二次的MouseDown事件。

只要在DblClick事件里调用MouseDown事件就能解决问题了。

添加一个变量
Dim Bn As Integer '记录按键信息

Private Sub Picture2_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)
Bn = Button
If Button <> 1 Then Exit Sub
Picture2.AutoRedraw = False
startx = X
starty = Y
End Sub

Private Sub Picture2_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
If Button <> 1 Then Exit Sub
Picture2.Refresh
Picture2.Line (startx, starty)-(X, Y)
End Sub

Private Sub Picture2_MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single)
If Button <> 1 Then Exit Sub
endx = X
endy = Y
Picture2.AutoRedraw = True
Picture2.Line (startx, starty)-(endx, endy)
End Sub

Private Sub Picture2_DblClick()
If Bn = 1 Then Call Picture2_MouseDown(1, 0, endx, endy)
End Sub