Delphi - 闲来无事,自己写个Timer玩玩

技术交流,DH讲解.

明天去坐火车,回家,今天就没有事做,本来在弄一个跨进程获取其他程序里面组件,如ListView,ListBox,Button等的信息,突然有个想法自己写个Timer,不用SetTimer函数,我们自己用个多线程也正好实现这个.反正前段时间多线程也弄得比较多,本来想单独讲讲的,现在就用个例子来说明吧.
写成一个控件:utTimer.pas

unit utTimer;

interface
uses
  Windows,SysUtils,Classes;

type
  THuangJackyTimerThread = class;
  THuangJackyTimer = class(TComponent)
  private
    FTimeInterval:Integer;
    FOnTimerDo:TNotifyEvent;
    FTimerThread:THuangJackyTimerThread;
    FEnable:Boolean;
    procedure SetEnable(bBool:Boolean);
    procedure SetTimeInterval(aValue:Integer);

    procedure StopThread;
    procedure StartThread;
  public
    constructor Create(AOwner: TComponent); override;
    destructor Destroy; override;
  published
    property TimeInterval:Integer  read FTimeInterval write SetTimeInterval;
    property OnTimerDo:TNotifyEvent  read FOnTimerDo write FOnTimerDo;
    property Enable:Boolean  read FEnable write SetEnable;
  end;

  THuangJackyTimerThread = class(TThread)
  private
    FTimer:THuangJackyTimer;
    FTerminateHandle,FExitHandle,FStartHandle,FStopHandle:Cardinal;

    procedure DoTimerEvent;
  protected
    procedure Execute;override;
  public
    constructor Create(AOwner: THuangJackyTimer);
    destructor Destroy; override;
  end;

procedure Register;


implementation

procedure Register;
begin
  RegisterComponents('HuangJacky',[THuangJackyTimer]);
end;

{ THuangJackyTimer }

constructor THuangJackyTimer.Create(AOwner: TComponent);
begin
  inherited;
  FTimeInterval:=1000;
  FTimerThread:=THuangJackyTimerThread.Create(Self);
  FTimerThread.Resume;
end;

destructor THuangJackyTimer.Destroy;
begin
  SetEvent(FTimerThread.FTerminateHandle);
  WaitForSingleObject(FTimerThread.FExitHandle,5000);
  FTimerThread.Free;
  inherited;
end;

procedure THuangJackyTimer.SetEnable(bBool: Boolean);
begin
  if Enable = bBool then
    Exit;
  if csDesigning in ComponentState then
    Exit;
  if Enable then
  begin
    StopThread;
    FEnable:=False;
  end
  else
  begin
    StartThread;
    FEnable:=True;
  end;
end;

procedure THuangJackyTimer.SetTimeInterval(aValue: Integer);
begin
  if FTimeInterval = aValue then
    Exit;
  InterlockedExchange(FTimeInterval,aValue);
end;

procedure THuangJackyTimer.StartThread;
begin
  SetEvent(FTimerThread.FStartHandle);
end;

procedure THuangJackyTimer.StopThread;
begin
  SetEvent(FTimerThread.FStopHandle)
end;

{ THuangJackyTimerThread }

constructor THuangJackyTimerThread.Create(AOwner: THuangJackyTimer);
var
  sTmp,sTmp1:string;
begin
  inherited Create(True);
  Assert(Assigned(AOwner));
  //自己创建,自己释放,这样能保证100%不内存泄露,个人习惯
  FreeOnTerminate:=False;
  FTimer:=AOwner;
  sTmp:=FTimer.Name;
  sTmp1:=DateTimeToStr(Now());
  FTerminateHandle:=CreateEvent(nil,True,False,PChar(sTmp + sTmp1 + 'T'));
  Assert(FTerminateHandle<>0);
  //用这个Event来通知主线程:Timer线程已经执行完了
  FExitHandle:=CreateEvent(nil,True,False,PChar(sTmp + sTmp1 + 'E'));
  Assert(FExitHandle<>0);
  FStartHandle:=CreateEvent(nil,True,False,PChar(sTmp + sTmp1 +'Sa'));
  Assert(FStartHandle<>0);
  FStopHandle:=CreateEvent(nil,True,False,PChar(sTmp + sTmp1 + 'So'));
  Assert(FStopHandle<>0);
end;

destructor THuangJackyTimerThread.Destroy;
begin
   CloseHandle(FStopHandle);
   CloseHandle(FStartHandle);
   CloseHandle(FExitHandle);
   CloseHandle(FTerminateHandle);
  inherited;
end;

procedure THuangJackyTimerThread.DoTimerEvent;
begin
  if Assigned(FTimer.OnTimerDo) then
    FTimer.OnTimerDo(FTimer);
end;

procedure THuangJackyTimerThread.Execute;
var
  Waits1:array[0..2] of Cardinal;
  Waits2:array[0..1] of Cardinal;

  procedure DoTerminate;
  begin
    ResetEvent(FTerminateHandle);
    Terminate;
  end;

begin
  Waits1[0]:=FStartHandle;
  Waits1[1]:=FTerminateHandle;
  Waits1[2]:=FStopHandle;
  Waits2[0]:=FStopHandle;
  Waits2[1]:=FTerminateHandle;
  //循环等待.
  while not Terminated do
    //每一次Wait后我们都需要判断下Terminate,不然在你等待的时候,线程就被Terminate了.
    //不过不判断也不要紧
    //因为Terminate只是将Terminated设置成True.
    //也就是如果不判断,就多运行一次.
    //但是这个例子里面因为内层也有一个While循环,所以必须判断
    case WaitForMultipleObjects(3,@Waits1,False,INFINITE) of
      WAIT_OBJECT_0 + 0:
        begin
          ResetEvent(FStartHandle);
          if Terminated then
            Break;
          while True do
          begin
            case WaitForMultipleObjects(2,@Waits2,False,FTimer.TimeInterval) of
              WAIT_OBJECT_0 + 0:
                begin
                  ResetEvent(FStopHandle);
                  Break
                end;
              WAIT_OBJECT_0 + 1:
                begin
                  DoTerminate;
                  Break;
                end;
            end;
            if Terminated then
              Break;
            //执行Timer事件.
            Synchronize(DoTimerEvent);
          end;
        end;
      WAIT_OBJECT_0 + 1:
        DoTerminate;
      WAIT_OBJECT_0 + 2:
        ResetEvent(FStopHandle);
    end;
  SetEvent(FExitHandle);
end;

end.

两百行的代码,比较简单,就是一个线程在循环等待事件,然后相应的事件做相应的事.
其实主要是想说如何使用线程,我不喜欢将线程的FreeOnTerminate设置为True,因为感觉不安全,心里不踏实呀.
测试例子:Unit1.pas

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs,utTimer;

type
  TForm1 = class(TForm)
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
    Timer:THuangJackyTimer;
    III:Integer;
    procedure DoTimer(S:TObject);
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.DoTimer(S: TObject);
begin
//这个Timer不存在重入的情况,所以不需要先设置Enable为True
  Caption:=IntToStr(III);
  Inc(III);
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  Timer:=THuangJackyTimer.Create(Self);
  Timer.TimeInterval:=2000;
  Timer.OnTimerDo:=DoTimer;
  Timer.Enable:=True;
end;

end.

D7和D2010上面都测试了一下,米有发现问题.
如果有什么问题欢迎拍砖.哈哈

我是DH.