Question

请教VB高手一个polyline的问题

Dim a(2001) As Single
For i = 0 To 2000
Picture1.Line (i, a(i))-(i + 1, a(i + 1)), vbRed
Next
上述的一个画线程序,请高手用polyline这个api写一下,我不会用这个API,谢谢啊.

Answer 1

首先是声名
Declare Function Polyline Lib "gdi32" Alias "Polyline" (ByVal hdc As Long, lpPoint As POINTAPI, ByVal nCount As Long) As Long

这里要用到hdc可以用getdc获得，hdc用完后用releasedc释放资源。所以这里还要声名这两个api

Declare Function GetDC Lib "user32" Alias "GetDC" (ByVal hwnd As Long) As Long

Declare Function ReleaseDC Lib "user32" Alias "ReleaseDC" (ByVal hwnd As Long, ByVal hdc As Long) As Long

这里用到一个自定义类型POINTAPI，同样需要声明

type POINTAPI
x as long
y as long
end type

然后就可以调用了。

比如你直接在屏幕上作画，那就这样
dim hdc as long ‘保存句柄用
dim points(3) as POINTAPI ’假设画三角
‘型， 三个点存在这个数组里
points(0).x=0
points(0).y=0
points(1).x=100
points(1).y=0
points(2).x=0
points(2).y=100

hdc=getdc(0)'获得句柄

Polyline hdc,points(0),3 '画三角形
'第一个参数表示句柄，第二个参数表示点的数组，第三个参数代表点的个数。

releasedc 0,hdc ’释放句柄

这样就可以了。

Answer 2

Private Declare Function Polyline Lib "gdi32" (ByVal hdc As Long, lpPoint As POINTAPI, ByVal nCount As Long) As Long
Private Type POINTAPI
x As Long
y As Long
End Type

Private Sub Command1_Click()
Dim p(5) As POINTAPI
p(0).x = 20
p(0).y = 20
p(1).x = 180
p(1).y = 50
p(2).x = 90
p(2).y = 170
Polyline Picture1.hdc, p(0), 3
End Sub