多线程编程(12) - 多线程同步之 Semaphore (信号对象)。 之前已经有了两种多线程的同步方法: 在本例中, 每点击按钮, 将建立一个信号总数为 5 的信号对象, 初始信号来自 Edit1; 同时有 5 个线程去排队. 本例也附上了 Delphi 中 TSemaphore 类的例子, 但没有过多地纠缠于细节, 是为了尽快理出多线程的整体思路. 本例效果图: 代码文件:unit Unit1; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls; type TForm1 = class(TForm) Button1: TButton; Edit1: TEdit; procedure Button1Click(Sender: TObject); procedure FormCreate(Sender: TObject); procedure FormDestroy(Sender: TObject); procedure Edit1KeyPress(Sender: TObject; var Key: Char); end; var Form1: TForm1; implementation {$R *.dfm} var f: Integer; {用这个变量协调一下各线程输出的位置} hSemaphore: THandle; {信号对象的句柄} function MyThreadFun(p: Pointer): DWORD; stdcall; var i,y: Integer; begin Inc(f); y := 20 * f; if WaitForSingleObject(hSemaphore, INFINITE) = WAIT_OBJECT_0 then begin for i := 0 to 1000 do begin Form1.Canvas.Lock; Form1.Canvas.TextOut(20, y, IntToStr(i)); Form1.Canvas.Unlock; Sleep(1); {以免 Canvas 忙不过来} end; end; ReleaseSemaphore(hSemaphore, 1, nil); Result := 0; end; procedure TForm1.Button1Click(Sender: TObject); var ThreadID: DWORD; begin {不知是不是之前创建过 Semaphore 对象, 假如有先关闭} CloseHandle(hSemaphore); {创建 Semaphore 对象} hSemaphore := CreateSemaphore(nil, StrToInt(Edit1.Text), 5, nil); Self.Repaint; f := 0; CreateThread(nil, 0, @MyThreadFun, nil, 0, ThreadID); CreateThread(nil, 0, @MyThreadFun, nil, 0, ThreadID); CreateThread(nil, 0, @MyThreadFun, nil, 0, ThreadID); CreateThread(nil, 0, @MyThreadFun, nil, 0, ThreadID); CreateThread(nil, 0, @MyThreadFun, nil, 0, ThreadID); end; {让 Edit 只接受 1 2 3 4 5 五个数} procedure TForm1.Edit1KeyPress(Sender: TObject; var Key: Char); begin if not CharInSet(Key, ['1'..'5']) then Key := #0; end; procedure TForm1.FormCreate(Sender: TObject); begin Edit1.Text := '1'; end; procedure TForm1.FormDestroy(Sender: TObject); begin CloseHandle(hSemaphore); end; end. 窗体文件:object Form1: TForm1 Left = 0 Top = 0 Caption = 'Form1' ClientHeight = 140 ClientWidth = 192 Color = clBtnFace Font.Charset = DEFAULT_CHARSET Font.Color = clWindowText Font.Height = -11 Font.Name = 'Tahoma' Font.Style = [] OldCreateOrder = False OnCreate = FormCreate PixelsPerInch = 96 TextHeight = 13 object Button1: TButton Left = 109 Top = 107 Width = 75 Height = 25 Caption = 'Button1' TabOrder = 0 OnClick = Button1Click end object Edit1: TEdit Left = 109 Top = 80 Width = 75 Height = 21 TabOrder = 1 Text = 'Edit1' OnKeyPress = Edit1KeyPress end end 再用 SyncObjs 单元下的 TSemaphore 类实现一次, 使用方法差不多, 运行效果也一样:unit Unit1; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls; type TForm1 = class(TForm) Button1: TButton; Edit1: TEdit; procedure Button1Click(Sender: TObject); procedure FormCreate(Sender: TObject); procedure FormDestroy(Sender: TObject); procedure Edit1KeyPress(Sender: TObject; var Key: Char); end; var Form1: TForm1; implementation {$R *.dfm} uses SyncObjs; var f: Integer; MySemaphore: TSemaphore; function MyThreadFun(p: Pointer): DWORD; stdcall; var i,y: Integer; begin Inc(f); y := 20 * f; if MySemaphore.WaitFor(INFINITE) = wrSignaled then begin for i := 0 to 1000 do begin Form1.Canvas.Lock; Form1.Canvas.TextOut(20, y, IntToStr(i)); Form1.Canvas.Unlock; Sleep(1); end; end; MySemaphore.Release; Result := 0; end; procedure TForm1.Button1Click(Sender: TObject); var ThreadID: DWORD; begin if Assigned(MySemaphore) then MySemaphore.Free; MySemaphore := TSemaphore.Create(nil, StrToInt(Edit1.Text), 5, ''); Self.Repaint; f := 0; CreateThread(nil, 0, @MyThreadFun, nil, 0, ThreadID); CreateThread(nil, 0, @MyThreadFun, nil, 0, ThreadID); CreateThread(nil, 0, @MyThreadFun, nil, 0, ThreadID); CreateThread(nil, 0, @MyThreadFun, nil, 0, ThreadID); CreateThread(nil, 0, @MyThreadFun, nil, 0, ThreadID); end; {让 Edit 只接受 1 2 3 4 5 五个数} procedure TForm1.Edit1KeyPress(Sender: TObject; var Key: Char); begin if not CharInSet(Key, ['1'..'5']) then Key := #0; end; procedure TForm1.FormCreate(Sender: TObject); begin Edit1.Text := '1'; end; procedure TForm1.FormDestroy(Sender: TObject); begin if Assigned(MySemaphore) then MySemaphore.Free; end; end. |
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