多线程编程(17) - 多线程同步之 WaitableTimer (等待定时器对象)[续三]

根据 WaitableTimer 的主要功用, 现在再把它放在 "线程同步" 的话题中讨论有点不合适了, 就要结束它.

//重新看看那个 APC 回调函数的格式:

procedure TimerAPCProc(

  lpArgToCompletionRoutine: Pointer;

  dwTimerLowValue, dwTimerHighValue: DWORD

); stdcall;


 
   

TimerAPCProc 的后两个参数其实是在传递一个值, 使用时要把它们合并为一个 TFileTime 类型的时间.
这个时间是 APC 函数被调用的时间, 稍稍修改上面一个例子看一下:

---

代码文件:

---

unit Unit1;



interface



uses

  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

  Dialogs, StdCtrls;



type

  TForm1 = class(TForm)

    Button1: TButton;

    Button2: TButton;

    procedure Button1Click(Sender: TObject);

    procedure Button2Click(Sender: TObject);

    procedure FormDestroy(Sender: TObject);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



var

  hTimer: THandle;



{APC 函数}

procedure TimerAPCProc(lpArgToCompletionRoutine: Pointer; dwTimerLowValue: DWORD;

  dwTimerHighValue: DWORD); stdcall;

var

  UTCFileTime,LocalFileTime: TFileTime;

  SystemTime: TSystemTime;

  DateTime: TDateTime;

begin

  {把 dwTimerLowValue 与 dwTimerHighValue 和并为一个 TFileTime 格式的时间}

  UTCFileTime.dwLowDateTime := dwTimerLowValue;

  UTCFileTime.dwHighDateTime := dwTimerHighValue;



  FileTimeToLocalFileTime(UTCFileTime, LocalFileTime); {从世界标准计时到本地时间}

  FileTimeToSystemTime(LocalFileTime, SystemTime);     {转到系统格式时间}

  DateTime := SystemTimeToDateTime(SystemTime);        {再转到 TDateTime}



  Form1.Text := DateTimeToStr(DateTime);

  SleepEx(INFINITE, True);

end;



{线程入口函数}

function MyThreadFun(p: Pointer): Integer; stdcall;

var

  DueTime: Int64;

begin

  DueTime := 0;

  if SetWaitableTimer(hTimer, DueTime, 1000, @TimerAPCProc, nil, False) then

  begin

    SleepEx(INFINITE, True);

  end;

  Result := 0;

end;



procedure TForm1.Button1Click(Sender: TObject);

var

  ID: DWORD;

begin

  if hTimer = 0 then  hTimer := CreateWaitableTimer(nil, True, nil);

  CreateThread(nil, 0, @MyThreadFun, nil, 0, ID);

end;



procedure TForm1.Button2Click(Sender: TObject);

begin

  CancelWaitableTimer(hTimer);

end;



procedure TForm1.FormDestroy(Sender: TObject);

begin

  CloseHandle(hTimer);

end;



end.


 
   

窗体文件:

---

object Form1: TForm1

  Left = 0

  Top = 0

  Caption = 'Form1'

  ClientHeight = 86

  ClientWidth = 256

  Color = clBtnFace

  Font.Charset = DEFAULT_CHARSET

  Font.Color = clWindowText

  Font.Height = -11

  Font.Name = 'Tahoma'

  Font.Style = []

  OldCreateOrder = False

  PixelsPerInch = 96

  TextHeight = 13

  object Button1: TButton

    Left = 23

    Top = 32

    Width = 97

    Height = 25

    Caption = #21551#21160#23450#26102#22120

    TabOrder = 0

    OnClick = Button1Click

  end

  object Button2: TButton

    Left = 134

    Top = 32

    Width = 97

    Height = 25

    Caption = #21462#28040#23450#26102#22120

    TabOrder = 1

    OnClick = Button2Click

  end

end


 
   

SetWaitableTimer 中回调函数后面的指针参数, 将被传递给 APC 函数的第一个参数;
作为指针它可以携带任何数据, 这里让它携带了一个坐标点(鼠标点击窗体的位置), 下例效果图:

---

代码文件:

---

unit Unit1;



interface



uses

  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

  Dialogs, StdCtrls;



type

  TForm1 = class(TForm)

    procedure FormDestroy(Sender: TObject);

    procedure FormMouseDown(Sender: TObject; Button: TMouseButton;

      Shift: TShiftState; X, Y: Integer);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



var

  hTimer: THandle;

  pt: TPoint;



{APC 函数}

procedure TimerAPCProc(lpArgToCompletionRoutine: Pointer; dwTimerLowValue: DWORD;

  dwTimerHighValue: DWORD); stdcall;

var

  UTCFileTime,LocalFileTime: TFileTime;

  SystemTime: TSystemTime;

  DateTime: TDateTime;

  pt2: TPoint;

begin

  UTCFileTime.dwLowDateTime := dwTimerLowValue;

  UTCFileTime.dwHighDateTime := dwTimerHighValue;



  FileTimeToLocalFileTime(UTCFileTime, LocalFileTime);

  FileTimeToSystemTime(LocalFileTime, SystemTime);

  DateTime := SystemTimeToDateTime(SystemTime);



  pt2 := PPoint(lpArgToCompletionRoutine)^; {接受指针参数}

  Form1.Canvas.Lock;

  Form1.Canvas.TextOut(pt2.X, pt2.Y, DateTimeToStr(DateTime));

  Form1.Canvas.Unlock;



  SleepEx(INFINITE, True);

end;



{线程入口函数}

function MyThreadFun(p: Pointer): Integer; stdcall;

var

  DueTime: Int64;

begin

  DueTime := 0;

  {参数 @pt 在这里是鼠标点击窗体时的坐标结构的指针, 它将传递给 APC 函数的第一个参数}

  if SetWaitableTimer(hTimer, DueTime, 1000, @TimerAPCProc, @pt, False) then

  begin

    SleepEx(INFINITE, True);

  end;

  Result := 0;

end;



{建立 WaitableTimer 对象和线程}

procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;

  Shift: TShiftState; X, Y: Integer);

var

  ID: DWORD;

begin

  pt := Point(X,Y); {在这里个全局的坐标点赋值}

  if hTimer = 0 then  hTimer := CreateWaitableTimer(nil, True, nil);

  CreateThread(nil, 0, @MyThreadFun, nil, 0, ID);

end;



procedure TForm1.FormDestroy(Sender: TObject);

begin

  CloseHandle(hTimer);

end;



end.


 
   

窗体文件:

---

object Form1: TForm1

  Left = 0

  Top = 0

  Caption = 'Form1'

  ClientHeight = 135

  ClientWidth = 195

  Color = clBtnFace

  Font.Charset = DEFAULT_CHARSET

  Font.Color = clWindowText

  Font.Height = -11

  Font.Name = 'Tahoma'

  Font.Style = []

  OldCreateOrder = False

  OnMouseDown = FormMouseDown

  PixelsPerInch = 96

  TextHeight = 13

end