用Visual Basic创建多线程应用程序

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用Visual Basic创建多线程应用程序

来源: 作者: 时间:2016-01-21 10:23 【

问题背景: 有时候我们做程序时有这样的需求:有一个需要运行时间很长的循环,那么程序只有等待循环运行结束后才执行别的程序代码,这样机器一直处于循环之中,而不能响应别的
问题背景:

  有时候我们做程序时有这样的需求:有一个需要运行时间很长的循环,那么程序只有等待循环运行结束后才执行别的程序代码,这样机器一直处于循环之中,而不能响应别的事情,对CPU资源来说是一种浪费,那么可不可以既让循环执行,又可以执行程序另外的一部分代码呢?答案是可以的,那就要用到多线程了。

  相关知识:

  进程:是指程序在一个数据集合上运行的过程,是操作进行资源分配和调度运行的一个独立单位,简单来说进程就是程序的一次执行。

  进程的两个基本属性:

  1.进程是一个可拥有资源的独立单位;

  2. 进程同时又是一个可以独立调度和分配的基本单位。

  操作系统中引入进程的目的是为了使多个程序并发执行,以改善资源利用率及提高系统的吞吐量。

  线程:线是进程中的一个实体,是被系统独立调度和分配的基本单位。线程自己基本上不拥有系统资源,只拥有一些在运行中必不可少的资源,但它可与同属一个进程的其他线程共享进程所拥有的全部资源。同一个进程中的多个线程之间可以并发执行。

  问题实现:

  VB可不可以创建多线程呢?答案:VB本身不可以,但用API函数VB可以实现。

  在VB中创建线程用到以下几个API函数:

创建线程API

此API经过改造,lpThreadAttributes改为Any型,lpStartAddress改为传值引用:

因为函数入口地址是由形参变量传递,如果用传址那将传递形参变量的地址而不是函数的入口地址

参数dwStackSize为应用程序堆栈大小,lpStartAddress为函数入口地址

Private Declare Function CreateThread Lib "kernel32" (ByVal lpThreadAttributes As Any, ByVal dwStackSize As Long, ByVal lpStartAddress As Long, lpParameter As Any, ByVal dwCreationFlags As Long, LpthreadId As Long) As Long

终止线程API

Private Declare Function TerminateThread Lib "kernel32" (ByVal hThread As Long, ByVal dwExitCode As Long) As Long

激活线程API,参数hThread为CreateThread创建的线程句柄

Private Declare Function ResumeThread Lib "kernel32" (ByVal hThread As Long) As Long

挂起线程API

Private Declare Function SuspendThread Lib "kernel32" (ByVal hThread As Long) As Long

  了解完上面的API函数后请看下面的实例:

  实例效果:此实例实现三个图片框的背景色一起变色。

  实例的窗体布局见图:


  程序的工程窗口:



源代码如下

  窗体中的代码:

Option Explicit

开始

Private Sub Command1_Click()

 On Error Resume Next

 With myThreadleft
  .Initialize AddressOf Fillleft 传递过程地址给线程
  .ThreadEnabled = True
 End With

 With myThreadright
  .Initialize AddressOf Fillright
  .ThreadEnabled = True
 End With

 With myThreadbottom
  .Initialize AddressOf Fillbottom
  .ThreadEnabled = True
 End With

 MsgBox "多线程正在运行...,看看图片框控件的变色效果!", 64, "信息"

 终止线程运行

 Set myThreadleft = Nothing
 Set myThreadright = Nothing
 Set myThreadbottom = Nothing

End Sub

结束

Private Sub Command2_Click()
 Unload Me
End Sub

模块中的代码:

Option Explicit

时间计数API

Private Declare Function GetTickCount Lib "kernel32" () As Long

声明cls_thread类的对象变量
Public myThreadleft As New cls_thread, myThreadright As New cls_thread, myThreadbottom As New cls_thread

Sub Main()
 Load Form1
 Form1.Show
End Sub

Public Sub Fillleft()
 Static Bkgcolor As Long
 Dim LongTick As Long, Longcounter As Long
 On Error Resume Next
 For Longcounter = 0 To 3000
  DoEvents
  Bkgcolor = Longcounter Mod 256
  Form1.Picture1.BackColor = RGB(Bkgcolor, 0, 0)
  LongTick = GetTickCount
  While GetTickCount - LongTick < 10 延时10毫秒,下同
  Wend
 Next
 Set myThreadleft = Nothing 如果循环结束则终止当前线程运行,下同
End Sub

Public Sub Fillright()
 Static Bkgcolor As Long
 Dim LongTickValue As Long, Longcounter As Long
 On Error Resume Next
 For Longcounter = 0 To 3000
  DoEvents
  Bkgcolor = Longcounter Mod 256
  Form1.Picture2.BackColor = RGB(0, Bkgcolor, 0)
  LongTickValue = GetTickCount
  While GetTickCount - LongTickValue < 10
  Wend
 Next
 Set myThreadright = Nothing
End Sub

Public Sub Fillbottom()
 Static Bkgcolor As Long
 Dim LongTick As Long, Longcounter As Long
 On Error Resume Next
 For Longcounter = 0 To 3000
  DoEvents
  Bkgcolor = Longcounter Mod 256
  Form1.Picture3.BackColor = RGB(0, 0, Bkgcolor)
  LongTick = GetTickCount
  While GetTickCount - LongTick < 10
  Wend
 Next
 Set myThreadright = Nothing
End Sub

类模块中的代码:

功能:创建多线程类,用于初始化线程。 类名:cls_Thread

参数:LongPointFunction 用于接收主调过程传递过来的函数地址值

调用方法:1.声明线程类对象变量 Dim mythread as cls_Thread

2.调用形式:With mythread

.Initialize AddressOf 自定义过程或函数名 (初始化线程) .

.ThreadEnabled = True (设置线程是否激活)

End With

3.终止调用: Set mythread = Nothing

Crate By : 陈宇 On 2004.5.10 Copyright(C).Ldt By CY-soft 2001--2004

Email:           

Test On: VB6.0+Win98 AND VB6.0+WinXP Its Pass !

Option Explicit

创建线程API

此API经过改造,lpThreadAttributes改为Any型,lpStartAddress改为传值引用:

因为函数的入口地址由形参变量传递,如果用传址那将传递形参变量的地址而不是函数的入口地址

Private Declare Function CreateThread Lib "kernel32" (ByVal lpThreadAttributes As Any, ByVal dwStackSize As Long, ByVal lpStartAddress As Long, lpParameter As Any, ByVal dwCreationFlags As Long, LpthreadId As Long) As Long

终止线程API

Private Declare Function TerminateThread Lib "kernel32" (ByVal hThread As Long, ByVal dwExitCode As Long) As Long

激活线程API

Private Declare Function ResumeThread Lib "kernel32" (ByVal hThread As Long) As Long

挂起线程API

Private Declare Function SuspendThread Lib "kernel32" (ByVal hThread As Long) As Long
Private Const CREATE_SUSPENDED = &H4 线程挂起常量

自定义线程结构类型

Private Type udtThread
 Handle As Long
 Enabled As Boolean
End Type

Private meTheard As udtThread

初始化线程
Public Sub Initialize(ByVal LongPointFunction As Long)

 Dim LongStackSize As Long, LongCreationFlags As Long, LpthreadId As Long, LongNull As Long
 On Error Resume Next
 LongNull = 0
 LongStackSize = 0
 LongCreationFlags = CREATE_SUSPENDED 创建线程后先挂起,由程序激活线程
 创建线程并返线程句柄
 meTheard.Handle = CreateThread(LongNull, LongStackSize, ByVal LongPointFunction, LongNull, LongCreationFlags, LpthreadId)

 If meTheard.Handle = LongNull Then
  MsgBox "线程创建失败!", 48, "错误"
 End If
End Sub

获取线程是否激活属性

Public Property Get ThreadEnabled() As Boolean
 On Error Resume Next
 Enabled = meTheard.Enabled
End Property

设置线程是否激活属性

Public Property Let Th
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