DELPHI 多线程同步几种方法

DELPHI 多线程（TThread类的实现）
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。

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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;
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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.

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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.
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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。

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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:=20f;
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.
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Semaphore(信号或叫信号量)

{DELPHI2007不支持信号量，DELPHI2009才开始支持}

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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.
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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。

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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:=20f;
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.
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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。