DELPHI 多线程（TThread类的实现）

之前学习了用API实现，让我们再学习下用DELPHI的TThread类。

先新建一个普通的工程，再新建一个线程类File>>New>>Othre>>Delphi File>Thread Object，取个名字，DELPHI会自动生成一个单元，我们只需往里简单添加功能代码，和在要使用的单元里实例引用即可。

为了节省篇幅，现把TMyThread类集成主窗体单元里，在窗体单元里声明类也是可以的。

例：用工作线程在窗体输出0~500000的数字。

 1 unit Unit1;
 2
 3 interface
 4
 5 uses
 6   Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
 7   Dialogs, StdCtrls;
 8
 9 type
10   TMyThread = class(TThread)
11   private
12     { Private declarations }
13   protected
14     procedure Execute; override; {执行}
15     procedure Run; {声明多一个过程，把功能代码写在这里再给Execute调用}
16   end;
17   TForm1 = class(TForm)
18     btn1: TButton;
19     procedure btn1Click(Sender: TObject);
20   private
21     { Private declarations }
22   public
23     { Public declarations }
24   end;
25
26
27
28 var
29   Form1: TForm1;
30
31
32 implementation
33
34 {$R *.dfm}
35
36 var
37   MyThread:TMyThread; {声明一个线程类对象]
38
39 procedure TMyThread.Execute;
40 begin
41   { Place thread code here }
42   FreeOnTerminate:=True; {加上这句线程用完了会自动注释}
43   Run;
44 end;
45
46 procedure TMyThread.Run;
47 var
48   i:integer;
49 begin
50   for i := 0 to 500000 do
51   begin
52     Form1.Canvas.Lock;
53     Form1.Canvas.TextOut(10,10,IntToStr(i));
54     Form1.Canvas.Unlock;
55   end;
56 end;
57
58 procedure TForm1.btn1Click(Sender: TObject);
59 begin
60   MyThread:=TMyThread.Create(False); {实例化这个类，为False时立即运行，为True时可加MyThread.Resume用来启动}
61 end;

CriticalSection(临界区)

uses SyncObjs;用TCriticalSection类的方法处理。

例：用三个线程，按顺序给ListBox添加0~99.

 1 unit Unit1;
 2
 3 interface
 4
 5 uses
 6   Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
 7   Dialogs, StdCtrls;
 8
 9 type
10   TMyThread = class(TThread)
11   private
12     { Private declarations }
13   protected
14     procedure Execute; override; {执行}
15     procedure Run;  {运行}
16   end;
17   TForm1 = class(TForm)
18     btn1: TButton;
19     lst1: TListBox;
20     procedure btn1Click(Sender: TObject);
21     procedure FormDestroy(Sender: TObject);
22   private
23     { Private declarations }
24   public
25     { Public declarations }
26   end;
27
28
29
30 var
31   Form1: TForm1;
32
33
34 implementation
35
36 {$R *.dfm}
37
38 uses SyncObjs;
39
40 var
41   MyThread:TMyThread;   {声明线程}
42   CS:TCriticalSection; {声明临界}
43
44
45 procedure TMyThread.Execute;
46 begin
47   { Place thread code here }
48   FreeOnTerminate:=True; {加上这句线程用完了会自动注释}
49   Run;     {运行}
50 end;
51
52 procedure TMyThread.Run;
53 var
54   i:integer;
55 begin
56   CS.Enter;  {我要用了，其它人等下}
57   for i := 0 to 100 - 1 do
58   begin
59     Form1.lst1.Items.Add(IntToStr(i));
60   end;
61   CS.Leave;  {我用完了，下一个}
62 end;
63
64 procedure TForm1.btn1Click(Sender: TObject);
65 begin
66   CS:=TCriticalSection.Create;     {实例化临界}
67   MyThread:=TMyThread.Create(False); {实例化这个类，为False时立即运行，为True时可加MyThread.Resume用来启动}
68   MyThread:=TMyThread.Create(False);
69   MyThread:=TMyThread.Create(False);
70 end;
71
72
73 procedure TForm1.FormDestroy(Sender: TObject);
74 begin
75   CS.Free;{释放临界体}
76 end;
77
78 end.

Mutex (互斥对象)

uses SyncObjs;用TMutex类的方法处理(把释放语句放在循环内外可以决定执行顺序)

例：互斥输出三个0~2000的数字到窗体在不同位置。

 1 unit Unit1;
 2
 3 interface
 4
 5 uses
 6   Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
 7   Dialogs, StdCtrls;
 8
 9 type
10   TMyThread = class(TThread)
11   private
12     { Private declarations }
13   protected
14     procedure Execute; override; {执行}
15     procedure Run;  {运行}
16   end;
17   TForm1 = class(TForm)
18     btn1: TButton;
19     procedure FormDestroy(Sender: TObject);
20     procedure btn1Click(Sender: TObject);
21   private
22     { Private declarations }
23   public
24     { Public declarations }
25   end;
26
27
28
29 var
30   Form1: TForm1;
31
32
33 implementation
34
35 {$R *.dfm}
36
37 uses SyncObjs;
38
39 var
40   MyThread:TMyThread;   {声明线程}
41   Mutex:TMutex; {声明互斥体}
42   f:integer;
43
44
45 procedure TMyThread.Execute;
46 begin
47   { Place thread code here }
48   FreeOnTerminate:=True; {加上这句线程用完了会自动注释}
49   Run;     {运行}
50 end;
51
52 procedure TMyThread.Run;
53 var
54   i,y:integer;
55 begin
56   Inc(f);
57   y:=20*f;
58   for i := 0 to 2000  do
59   begin
60     if Mutex.WaitFor(INFINITE)=wrSignaled then   {判断函数，能用时就用}
61     begin
62       Form1.Canvas.Lock;
63       Form1.Canvas.TextOut(10,y,IntToStr(i));
64       Form1.Canvas.Unlock;
65       Sleep(1);
66       Mutex.Release; {释放，谁来接下去用}
67     end;
68   end;
69 end;
70
71 procedure TForm1.btn1Click(Sender: TObject);
72 begin
73   f:=0;
74   Repaint;
75   Mutex:=TMutex.Create(False);  {参数为是否让创建者拥有该互斥体，一般为False}
76   MyThread:=TMyThread.Create(False);
77   MyThread:=TMyThread.Create(False);
78   MyThread:=TMyThread.Create(False);
79 end;
80
81 procedure TForm1.FormDestroy(Sender: TObject);
82 begin
83   Mutex.Free;{释放互斥体}
84 end;
85
86 end.

Semaphore(信号或叫信号量)

{DELPHI2007不支持信号量，DELPHI2009才开始支持}

 1 unit Unit1;
 2
 3 interface
 4
 5 uses
 6   Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
 7   Dialogs, StdCtrls;
 8
 9 type
10   TForm1 = class(TForm)
11     Button1: TButton;
12     Edit1: TEdit;
13     procedure Button1Click(Sender: TObject);
14     procedure FormCreate(Sender: TObject);
15     procedure FormDestroy(Sender: TObject);
16     procedure Edit1KeyPress(Sender: TObject; var Key: Char);
17   end;
18
19 var
20   Form1: TForm1;
21
22 implementation
23
24 {$R *.dfm}
25
26 uses SyncObjs;
27 var
28   f: Integer;
29   MySemaphore: TSemaphore;
30
31 function MyThreadFun(p: Pointer): DWORD; stdcall;
32 var
33   i,y: Integer;
34 begin
35   Inc(f);
36   y := 20 * f;
37   if MySemaphore.WaitFor(INFINITE) = wrSignaled then
38   begin
39     for i := 0 to 1000 do
40     begin
41       Form1.Canvas.Lock;
42       Form1.Canvas.TextOut(20, y, IntToStr(i));
43       Form1.Canvas.Unlock;
44       Sleep(1);
45     end;
46   end;
47   MySemaphore.Release;
48   Result := 0;
49 end;
50
51 procedure TForm1.Button1Click(Sender: TObject);
52 var
53   ThreadID: DWORD;
54 begin
55   if Assigned(MySemaphore) then MySemaphore.Free;
56   MySemaphore := TSemaphore.Create(nil, StrToInt(Edit1.Text), 5, ''); {创建，参数一为安全默认为nil，参数2可以填写运行多少线程，参数3是运行总数，参数4可命名用于多进程}
57
58   Self.Repaint;
59   f := 0;
60   CreateThread(nil, 0, @MyThreadFun, nil, 0, ThreadID);
61   CreateThread(nil, 0, @MyThreadFun, nil, 0, ThreadID);
62   CreateThread(nil, 0, @MyThreadFun, nil, 0, ThreadID);
63   CreateThread(nil, 0, @MyThreadFun, nil, 0, ThreadID);
64   CreateThread(nil, 0, @MyThreadFun, nil, 0, ThreadID);
65 end;
66
67 {让 Edit 只接受 1 2 3 4 5 五个数}
68 procedure TForm1.Edit1KeyPress(Sender: TObject; var Key: Char);
69 begin
70   if not CharInSet(Key, ['1'..'5']) then Key := #0;
71 end;
72
73 procedure TForm1.FormCreate(Sender: TObject);
74 begin
75   Edit1.Text := '1';
76 end;
77
78 procedure TForm1.FormDestroy(Sender: TObject);
79 begin
80   if Assigned(MySemaphore) then MySemaphore.Free;
81 end;
82
83 end.

 Event (事件对象)

注：相比API的处理方式，此类没有启动步进一次后暂停的方法。

  1 unit Unit1;
  2
  3 interface
  4
  5 uses
  6   Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  7   Dialogs, StdCtrls;
  8
  9 type
 10   TMyThread = class(TThread)
 11   private
 12     { Private declarations }
 13   protected
 14     procedure Execute; override;
 15     procedure Run;
 16   end;
 17
 18   TForm1 = class(TForm)
 19     btn1: TButton;
 20     btn2: TButton;
 21     btn3: TButton;
 22     btn4: TButton;
 23     procedure btn1Click(Sender: TObject);
 24     procedure FormDestroy(Sender: TObject);
 25     procedure btn2Click(Sender: TObject);
 26     procedure btn3Click(Sender: TObject);
 27     procedure btn4Click(Sender: TObject);
 28     procedure FormCreate(Sender: TObject);
 29   private
 30     { Private declarations }
 31   public
 32     { Public declarations }
 33   end;
 34
 35 var
 36   Form1: TForm1;
 37
 38 implementation
 39
 40 {$R *.dfm}
 41
 42 uses SyncObjs;
 43
 44 var
 45   f:integer;
 46   MyEvent:TEvent;
 47   MyThread:TMyThread;
 48
 49 { TMyThread }
 50
 51
 52 procedure TMyThread.Execute;
 53 begin
 54   inherited;
 55   FreeOnTerminate:=True; {线程使用完自己注销}
 56   Run;
 57 end;
 58
 59 procedure TMyThread.Run;
 60 var
 61   i,y:integer;
 62 begin
 63   Inc(f);
 64   y:=20*f;
 65
 66   for i := 0 to 20000 do
 67   begin
 68     if MyEvent.WaitFor(INFINITE)=wrSignaled then    {判断事件在用没，配合事件的启动和暂停，对事件相关线程起统一控制}
 69     begin
 70       Form1.Canvas.lock;
 71       Form1.Canvas.TextOut(10,y,IntToStr(i));
 72       Form1.Canvas.Unlock;
 73       Sleep(1);
 74     end;
 75
 76   end;
 77
 78 end;
 79
 80 procedure TForm1.btn1Click(Sender: TObject);
 81 begin
 82   Repaint;
 83   f:=0;
 84   if Assigned(MyEvent) then MyEvent.Free;    {如果有，就先销毁}
 85
 86   {参数1安全设置，一般为空；参数2为True时可手动控制暂停，为Flase时对象控制一次后立即暂停
 87   参数3为True时对象建立后即可运行，为false时对象建立后控制为暂停状态，参数4为对象名称，用于跨进程，不用时默认''}
 88   MyEvent:=TEvent.Create(nil,True,True,'');   {创建事件}
 89
 90 end;
 91
 92 procedure TForm1.btn2Click(Sender: TObject);
 93 var
 94   ID:DWORD;
 95 begin
 96   MyThread:=TMyThread.Create(False);      {创建线程}
 97 end;
 98
 99 procedure TForm1.btn3Click(Sender: TObject);
100 begin
101   MyEvent.SetEvent;    {启动}  {事件类没有PulseEvent启动一次后轻描谈写}
102 end;
103
104 procedure TForm1.btn4Click(Sender: TObject);
105 begin
106   MyEvent.ResetEvent;  {暂停}
107 end;
108
109 procedure TForm1.FormCreate(Sender: TObject);
110 begin
111    btn1.Caption:='创建事件';
112    btn2.Caption:='创建线程';
113    btn3.Caption:='启动';
114    btn4.Caption:='暂停';
115 end;
116
117 procedure TForm1.FormDestroy(Sender: TObject);
118 begin
119   MyEvent.Free;        {释放}
120 end;
121
122 end.

总结：

多线程用TThread类以及Uses syncobjs后使用的 TCriticalSection (临界区)，TMutex(互斥体)，TSemaphore (信号对象，D2009才开始有)，TEvent (事件对象)很多都是引用了API的方法进行了一定的简化，不过也有部分功能的缺失，如Event (事件对象)缺少了启动步进一次后暂停的功能，不过基本在同步上已经够用了，另外在TThread类声明的Execute过程里，加上FreeOnTerminate := True;这句会让线程执行完后自动释放，还可以把功能代码的方法套在Synchronize()里，用于同步一些非线程安全的控件对象，避免多个线程同时对一个对象操作引发的问题。