我想做一个画动态圆的小程序,但遇到一点问题,请各位大虾帮忙看一下.
要求:1.鼠标左键按下确定圆心,拖动显示虚线圆,鼠标抬起完成画圆
2.画下一个圆的时候,上一个圆仍然存在
程序如下:
Dim X0 As Single, Y0 As Single, R As Single
Dim IsDown As Boolean

Private Sub Form_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)
X0 = X
Y0 = Y
IsDown = True
End Sub

Private Sub Form_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
If IsDown = True Then
DrawStyle = 2
R = ((X - X0) ^ 2 + (Y - Y0) ^ 2) ^ 0.5
Cls
Circle (X0, Y0), R
End If
End Sub

Private Sub Form_MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single)
IsDown = False
DrawStyle = 0
Cls
Circle (X0, Y0), R
End Sub

问题:以上程序虽然能实现"要求1",但是每当画下一个圆的时候,上一个画的圆都被清除掉了,"要求2"实现不了.
我自己觉得应该是Cls语句用的不对,但我又找不出其他的替代方法,请高手帮忙改一下.

Dim X0 As Single, Y0 As Single, R As Single
Dim IsDown As Boolean

Private Sub Form_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)
X0 = X
Y0 = Y
IsDown = True
End Sub

Private Sub Form_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
If IsDown = True Then
DrawStyle = 2
R = ((X - X0) ^ 2 + (Y - Y0) ^ 2) ^ 0.5
End If
End Sub

Private Sub Form_MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single)
IsDown = False
DrawStyle = 0
Circle (X0, Y0), R
End Sub

谢谢二楼斑竹的回贴
不过这样改动后,"要求2"的问题虽然解决了,但"要求1"的鼠标左
键拖动时的"动态"显示就实现不了了.
我说的"动态"显示过程详细点描述就是:按下鼠标左键以后拖动,
而随着鼠标的拖动,会产生虚线形式的圆,当鼠标抬起的时候,才正式
生成实线圆.
可以的话再帮我看看,谢谢了~

依然用你原來的代碼.... 但在 MoveUp 事件中更正如下:

Private Sub Form_MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single)
IsDown = False
DrawStyle = 0
Cls
Me.AutoRedraw = True
Circle (X0, Y0), R
Me.Refresh
Me.AutoRedraw = False
End Sub

这不能只用 Line 方法解决。这个程序用了 Line 控件。
有一个问题是：如果按动鼠标画圆时，先放大了圆又缩小了圆，然后再拖大一些圆最后放下，画出来的圆会比原定的要大些

[此贴子已经被作者于2006-7-5 21:56:23编辑过]

四楼的yeshirow:按照你的修改,要求都能够实现了,谢谢你的帮助

也谢谢五楼的黑侠的回贴

强顶！4楼的回帖也帮我解决了困扰我很久的动态画图的问题！
我当时用的擦除对方法实现动态拖动大小的方法，可是以前画的某些线会被擦掉一部分！

Me.AutoRedraw = True
Circle (X0, Y0), R
Me.Refresh
Me.AutoRedraw = False

这方法真的很好！谢谢yeshirow！