delphi 多線程之 TEvent 和 TLightweightEvent

unit Unit1;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls,  system.SyncObjs;

type
  TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    Memo1: TMemo;
    CheckBox1: TCheckBox;
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure CheckBox1Click(Sender: TObject);
  private
  public
    { Public declarations }
  end;

  TMyThread = class(TThread)
  protected
    procedure Execute; override;
  end;

var
  Form1: TForm1;
  AEvent: TEvent;
  MyThread: TMyThread;

implementation

{$R *.dfm}

procedure Log(Msg: string);
begin
  TThread.Synchronize(nil, procedure begin
    Form1.Memo1.Lines.Add(Msg);
  end);
end;

{ TMyThread }

procedure TMyThread.Execute;
begin
  while not Terminated do
  begin
    AEvent.Acquire;
    Log(DateTimeToStr(Now));
    TThread.Sleep(500);
  end;
  Log('Exit');
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  AEvent.SetEvent;
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  AEvent.ResetEvent;
end;

procedure TForm1.CheckBox1Click(Sender: TObject);
begin
  MyThread.Terminate;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  Memo1.Clear;
  AEvent := TEvent.Create(nil, False, False, '');
  MyThread := TMyThread.Create(False);
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  if not MyThread.Finished then
  begin
    //確保線程正常退出
    MyThread.Terminate;
    AEvent.SetEvent;
    MyThread.WaitFor;
  end;
  MyThread.Free;

  AEvent.Free;
end;

end.

 

AEvent := TEvent.Create(nil, False, False, '');

第一個False, 線程是否可以執行一次. 如何為True,相當於 do while, 如果為 False , 相當於 while .
第二個False, 相當於線程是否可以直接運行，不需要SetEvent. 如果為 True , 則必須調用 SetEvent 后，線程才能運行。也就是線程啟動后就被阻塞住。
當兩個同時為 False 時， 就可以實現類似 PulseOneEvent 的功能。



TLightweightEvent 和 TEvent 基本上是一樣的，它是從 .NET中的 System.Threading.ManualResetEventSlim 學來的。對於多核，短時間間隔效率更好，可參考 MSDN 。