[Delphi]多线程编程多线程同步之CriticalSection(临界区)

先看一段程序, 代码文件: unit Unit1; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, s, Dialogs, StdCtrls; type T1 = class(T) ListBox1: TListBox; Button1: TButton; procedure Create(Sender: TObject); procedure Button1Click(Sender: TObject); end; var 1: T1; implementation {$R *.dfm} function MyThreadFun(p: Pointer): DWORD; stdcall; var i: Integer; begin for i := 0 to 99 do 1.ListBox1.Items.Add(IntToStr (i)); Result := 0; end; procedure T1.Button1Click(Sender: TObject); var ID: DWORD; begin CreateThread(nil, 0, @MyThreadFun, nil, 0, ID); CreateThread(nil, 0, @MyThreadFun, nil, 0, ID); CreateThread(nil, 0, @MyThreadFun, nil, 0, ID); end; procedure T1.Create(Sender: TObject); begin ListBox1.Align := alLeft; end; end. 窗体文件: object 1: T1 Left = 0 Top = 0 Caption = 1 ClientHeight = 154 ClientWidth = 214 Color = clBtnFace Font.Charset = DEFAULT_CHARSET Font.Color = clWindowText Font.Height = -11 Font.Name = Tahoma Font.Style = [] OldCreateOrder = False OnCreate = Create PixelsPerInch = 96 TextHeight = 13 object ListBox1: TListBox Left = 9 Top = 9 Width = 121 Height = 97 ItemHeight = 13 TabOrder = 0 end object Button1: TButton Left = 131 Top = 112 Width = 75 Height = 25 Caption = Button1 TabOrder = 1 OnClick = Button1Click end end 在这段程序中, 有三个线程几乎是同时建立, 向窗体中的 ListBox1 中写数据, 最后写出 的结果是这样的: 能不能让它们别打架, 一个完了另一个再来? 这就要用到多线程的同步技术. 前面说过, 最简单的同步手段就是 “临界区“. 先说这个 “同步“(Synchronize), 首先这个名字起的不好, 我们好像需要的是 “异步“; 其 实异步也不准确. 管它叫什么名字呢, 它的目的就是保证不冲突、有次序、都发生. “临界区“(CriticalSection): 当把一段代码放入一个临界区, 线程执行到临界区时就独占 了, 让其他也要执行此代码的线程先等等; 这和前面用的 Lock 和 UnLock 差不多; 使 用格式如下: var CS: TRTLCriticalSection; {声明一个 TRTLCriticalSection 结构类型变量; 它应该是全局的} InitializeCriticalSection(CS); {初始化} EnterCriticalSection(CS); {开始: 轮到我了其他线程走开} LeaveCriticalSection(CS); {结束: 其他线程可以来了} DeleteCriticalSection(CS); {删除: 注意不能过早删除} //也可用 TryEnterCriticalSection 替代 EnterCriticalSection. 用上临界区, 重写上面的代码, 运行效果图: 代码文件: unit Unit1; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, s, Dialogs, StdCtrls; type T1 = class(T) ListBox1: TListBox; Button1: TButton; procedure Create(Sender: TObject); procedure Destroy(Sender: TObject); procedure Button1Click(Sender: TObject); end; var 1: T1; implementation {$R *.dfm} var CS: TRTLCriticalSection; function MyThreadFun(p: Pointer): DWORD; stdcall; var i: Integer; begin EnterCriticalSection(CS); for i := 0 to 99 do 1.ListBox1.Items.Add(IntToStr (i)); LeaveCriticalSection(CS); Result := 0; end; procedure T1.Button1Click(Sender: TObject); var ID: DWORD; begin CreateThread(nil, 0, @MyThreadFun, nil, 0, ID); CreateThread(nil, 0, @MyThreadFun, nil, 0, ID); CreateThread(nil, 0, @MyThreadFun, nil, 0, ID); end; procedure T1.Create(Sender: TObject); begin ListBox1.Align := alLeft; InitializeCriticalSection(CS); end; procedure T1.Destroy(Sender: TObject); begin DeleteCriticalSection(CS); end; end. Delphi 在 SyncO