vb实现多线程！
昨晚2:30的时候还没睡着，觉得有必要把vb编写多线程程序再次写一次；主要是以前忽略的细节和重要的环节；今天在公司打开一年多没用的vb，写了如下的代码；想写多线程的朋友可以调试一下看看，关于多线程的任务模式，同步和互斥，临界资源和临界区（文中提到）欢迎跟帖讨论；
'请将该部分数据保存为 FORM1.frm 文件
VERSION 5.00
Begin VB.Form Form1
Caption = "多线程"
ClientHeight = 3195
ClientLeft = 60
ClientTop = 345
ClientWidth = 6450
LinkTopic = "Form1"
ScaleHeight = 3195
ScaleWidth = 6450
StartUpPosition = 3 '窗口缺省
Begin VB.TextBox Text1
Height = 270
Left = 960
TabIndex = 2
Text = "2"
Top = 2760
Width = 2415
End
Begin VB.CommandButton Command2
Caption = "返回"
Height = 255
Left = 3480
TabIndex = 1
Top = 2760
Width = 1455
End
Begin VB.CommandButton Command1
Caption = "Start Count"
Height = 255
Left = 3480
TabIndex = 0
Top = 240
Width = 1455
End
Begin VB.Label Label1
AutoSize = -1 'True
Caption = "主线程执行结果测试:"
Height = 180
Left = 600
TabIndex = 3
Top = 2400
Width = 1710
End
End
Attribute VB_Name = "Form1"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = False
Private Sub Command1_Click()
'声明了线程ID
Dim threadid1 As Long
Dim threadid2 As Long
'参数一，lpThreadAttributes 线程安全属性，传递为NULL
'参数二，dwStackSize ，线程堆栈大小，可以为0，表示堆栈和此应用堆栈相同
'参数三，lpstartAddress ，执行函数地址，用AddressOf 获取
'参数四，lpParameter ，执行函数的参数地址，可以是一个记录或者是别的类型，用VarPtr获取参数地址（varptr为未公开函数）！！
'参数五，dwCreationFlags ，表示线程创建后的状态！，0表示立即运行，create_SUSPENDED表示线程挂起
'参数六，lpThreadID 表示分配给线程的线程号
Call CreateThread(Null, ByVal O&, AddressOf Module1.OutText1, VarPtr(0), ByVal 0&, threadid1)
Call CreateThread(Null, ByVal 0&, AddressOf Module1.OutText2, VarPtr(0), ByVal 0&, threadid2)
End Sub
Private Sub Command2_Click()
'该事件运行于主线程！
Dim i As Long
i = CLng(Text1.Text)
Text1.Text = CStr(i * i) '不要点击次数太多，LONG 类型会溢出
End Sub
Private Sub Form_Load()
'保存窗体句柄全局变量，用于在form 上绘图
formhandle = Form1.hwnd
End Sub
----------------------------------
'请将该部分数据保存为 Module1.bas 文件
Attribute VB_Name = "Module1"
'线程安全属性数据结构；
Public Type SECURITY_ATTRIBUTES
nLength As Long
lpSecurityDescriptor As Long
bInheritHandle As Long
End Type
'这个是用于多线程访问临界资源同步Api的数据结构
Public Type CRITICAL_SECTION
dummy As Long
End Type
'为什么用GDI 函数绘图？原因等下再讲
Public Declare Function GetDC Lib "user32" (ByVal hwnd As Long) As Long
Public Declare Function SetBkColor Lib "gdi32" (ByVal hdc As Long, ByVal crColor As Long) As Long
Public Declare Function TextOut Lib "gdi32" Alias "TextOutA" (ByVal hdc As Long, ByVal x As Long, ByVal y As Long, ByVal lpString As String, ByVal nCount As Long) As Long
Public Declare Function ReleaseDC Lib "user32" (ByVal hwnd As Long, ByVal hdc As Long) As Long
'请注意；createThread APi声明已被我修改过，修改的地方请自行参照APIView复制的内容
Public Declare Function CreateThread Lib "kernel32" (lpThreadAttributes As Any, ByVal dwStackSize As Long, ByVal lpStartAddress As Long, ByVal lpParameter As Long, ByVal dwCreationFlags As Long, lpThreadId As Long) As Long
'这个是sleep,作用就是让两个线程绘图频率不一致，效果才明显。
Public Declare Sub Sleep Lib "kernel32" (ByVal dwMilliseconds As Long)
Public Declare Sub EnterCriticalSection Lib "kernel32" (lpCriticalSection As CRITICAL_SECTION) '进入临界区
Public Declare Sub LeaveCriticalSection Lib "kernel32" (lpCriticalSection As CRITICAL_SECTION) '离开临界区
'几个重要的函数举例
'ObjPtr：返回对象实例私有域的地址。
'StrPtr：返回字符串第一个字的地址。
'VarPtr：返回变量的地址。
'全局的form的句柄！
Public formhandle As Long
'临界数据结构
Public sect As CRITICAL_SECTION
Sub OutText1() '过程一
Dim i As Long
Dim dc As Long
Dim s As String
dc = GetDC(formhandle) '获取窗体句柄的DC
For i = 1 To 100000
s = CStr(i)
Call SetBkColor(dc, &HF0F0F0) '设置绘制区域的背景色，也起清除作用
Call TextOut(dc, 10, 10, s, Len(s)) '输出文本！
Call Sleep(40) '等待
Next
Call ReleaseDC(formhandle, dc) '释放资源！
' Call EnterCriticalSection(sect)
' 上下表示该处为临界区，如果要对工程全局变量做操作，最好在该区域内
' 否则线程同步过程中，非常容易让程序崩溃
' Call LeaveCriticalSection(sect)
End Sub
Sub OutText2() '和过程一类似
Dim i As Long
Dim dc As Long
Dim s As String
dc = GetDC(formhandle)
For i = 1 To 100000
s = CStr(i)
Call SetBkColor(dc, &HF0F0F0)
Call TextOut(dc, 10, 80, s, Len(s)) '文本位置改变了
Call Sleep(20) '延时改变了
Next
Call ReleaseDC(formhandle, dc)
' Call EnterCriticalSection(sect)
' Call LeaveCriticalSection(sect)
End Sub
'关于为何使用gdi 函数输出文本，这是一个很重要的内容；
'程序在记数时用了难用的TextOut 函数，而没有使用标签控件，这是因为
'vb的组件不都是线程安全的，当多线程访问不是线程安全的组件，那么会
'产生严重错误。
