在前面例子的基础上, 探讨新问题.
假如我们想让几个线程(例子中是 3 个)依次执行, 我们可以使用临界区、信号、互斥等手段;
但下面第一个例子什么同步工具都没用, 也达到了目的; 方法是: 让前一个线程在结束前顺便启动下一个线程.
第二个例子使用了互斥对象配合 WaitForSingleObject 函数, 也达到相似的目的.
效果图(两个例子的效果图差不多, 但第二个例子的执行顺序不好保证):
![](https://www.cnblogs.com/images/cnblogs_com/del/174185/o_0921906.gif)
第一个例子的代码文件:
unit Unit1; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls, ExtCtrls; type TForm1 = class(TForm) PaintBox1: TPaintBox; PaintBox2: TPaintBox; PaintBox3: TPaintBox; Button1: TButton; procedure Button1Click(Sender: TObject); procedure FormDestroy(Sender: TObject); end; var Form1: TForm1; implementation {$R *.dfm} const colors: array[0..2] of TColor = (clRed, clGreen, clBlue); var hArr: array[0..2] of THandle; panitArr: array[0..2] of TPaintBox; function ThreadFun(p: Pointer): Integer; stdcall; var i,n,x1,y1,x2,y2: Integer; ThreadID: DWORD; begin n := Integer(p); panitArr[n].Color := colors[n]; for i := 0 to 50 do with panitArr[n] do begin x1 := Random(Width); y1 := Random(Height); x2 := Random(Width); y2 := Random(Height); Canvas.Lock; Canvas.Ellipse(x1,y1,x2,y2); Canvas.Unlock; Sleep(2); end; {在前一个线程收尾时, 如果新建线程不超过 3 个就继续建立} Inc(n); if n < 3 then hArr[n] := CreateThread(nil, 0, @ThreadFun, Ptr(n), 0, ThreadID); Result := 0; end; procedure TForm1.Button1Click(Sender: TObject); var ID: DWORD; begin panitArr[0] := PaintBox1; panitArr[1] := PaintBox2; panitArr[2] := PaintBox3; {开始只建立了一个线程, 并传入 0 参数作为标识} hArr[0] := CreateThread(nil, 0, @ThreadFun, Ptr(0), 0, ID); end; procedure TForm1.FormDestroy(Sender: TObject); var i: Integer; begin for i := 0 to Length(hArr) - 1 do CloseHandle(hArr[i]); end; end.
窗体文件:
object Form1: TForm1 Left = 0 Top = 0 Caption = 'Form1' ClientHeight = 156 ClientWidth = 321 Color = clBtnFace Font.Charset = DEFAULT_CHARSET Font.Color = clWindowText Font.Height = -11 Font.Name = 'Tahoma' Font.Style = [] OldCreateOrder = False OnDestroy = FormDestroy PixelsPerInch = 96 TextHeight = 13 object PaintBox1: TPaintBox Left = 8 Top = 8 Width = 97 Height = 113 end object PaintBox2: TPaintBox Left = 111 Top = 8 Width = 98 Height = 113 end object PaintBox3: TPaintBox Left = 215 Top = 8 Width = 98 Height = 113 end object Button1: TButton Left = 238 Top = 126 Width = 75 Height = 25 Caption = 'Button1' TabOrder = 0 OnClick = Button1Click end end
第一个例子的代码文件(窗体同上):
unit Unit1; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls, ExtCtrls; type TForm1 = class(TForm) PaintBox1: TPaintBox; PaintBox2: TPaintBox; PaintBox3: TPaintBox; Button1: TButton; procedure Button1Click(Sender: TObject); procedure FormDestroy(Sender: TObject); end; var Form1: TForm1; implementation {$R *.dfm} const colors: array[0..2] of TColor = (clRed, clGreen, clBlue); var hArr: array[0..2] of THandle; panitArr: array[0..2] of TPaintBox; hMutex: THandle; {互斥对象的句柄} function ThreadFun(p: Pointer): Integer; stdcall; var i,n,x1,y1,x2,y2: Integer; begin n := Integer(p); panitArr[n].Color := colors[n]; if WaitForSingleObject(hMutex, INFINITE) = WAIT_OBJECT_0 then begin for i := 0 to 50 do with panitArr[n] do begin x1 := Random(Width); y1 := Random(Height); x2 := Random(Width); y2 := Random(Height); Canvas.Lock; Canvas.Ellipse(x1,y1,x2,y2); Canvas.Unlock; Sleep(10); end; ReleaseMutex(hMutex); end; Result := 0; end; procedure TForm1.Button1Click(Sender: TObject); var ID: DWORD; i: Integer; begin panitArr[0] := PaintBox1; panitArr[1] := PaintBox2; panitArr[2] := PaintBox3; CloseHandle(hMutex); hMutex := CreateMutex(nil, False, nil); for i := 0 to Length(hArr) - 1 do hArr[i] := CreateThread(nil, 0, @ThreadFun, Ptr(i), 0, ID); end; procedure TForm1.FormDestroy(Sender: TObject); var i: Integer; begin CloseHandle(hMutex); for i := 0 to Length(hArr) - 1 do CloseHandle(hArr[i]); end; end.