mirror of
https://gitlab.com/freepascal.org/lazarus/lazarus.git
synced 2025-05-11 01:43:50 +02:00
122 lines
3.7 KiB
ObjectPascal
122 lines
3.7 KiB
ObjectPascal
{
|
|
***************************************************************************
|
|
* *
|
|
* This source is free software; you can redistribute it and/or modify *
|
|
* it under the terms of the GNU General Public License as published by *
|
|
* the Free Software Foundation; either version 2 of the License, or *
|
|
* (at your option) any later version. *
|
|
* *
|
|
* This code is distributed in the hope that it will be useful, but *
|
|
* WITHOUT ANY WARRANTY; without even the implied warranty of *
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU *
|
|
* General Public License for more details. *
|
|
* *
|
|
* A copy of the GNU General Public License is available on the World *
|
|
* Wide Web at <http://www.gnu.org/copyleft/gpl.html>. You can also *
|
|
* obtain it by writing to the Free Software Foundation, *
|
|
* Inc., 51 Franklin Street - Fifth Floor, Boston, MA 02110-1335, USA. *
|
|
* *
|
|
***************************************************************************
|
|
|
|
Abstract:
|
|
Demo to show, how to start a thread and how synchronize with the main
|
|
thread.
|
|
Important: In most (all?) Unix like systems, the cthread unit must be added
|
|
to the uses section of the .lpr file. Further, cmem is likely to
|
|
be significently faster so add it as well. Due to how the units
|
|
work a sensible order is cmem, cthreads and then perhaps cwstrings.
|
|
But note that heaptrc does not work with cmem so comment it out
|
|
while testing/debugging.
|
|
}
|
|
unit MainUnit;
|
|
|
|
{$mode objfpc}{$H+}
|
|
|
|
interface
|
|
|
|
uses
|
|
Classes, SysUtils, Forms, Controls, Graphics, Dialogs;
|
|
|
|
type
|
|
|
|
{ TMyThread }
|
|
|
|
TMyThread = class(TThread)
|
|
private
|
|
fStatusText: string;
|
|
procedure ShowStatus;
|
|
protected
|
|
procedure Execute; override;
|
|
public
|
|
constructor Create(CreateSuspended: boolean);
|
|
end;
|
|
|
|
{ TForm1 }
|
|
|
|
TForm1 = class(TForm)
|
|
procedure FormCreate(Sender: TObject);
|
|
private
|
|
public
|
|
end;
|
|
|
|
var
|
|
Form1: TForm1;
|
|
|
|
implementation
|
|
|
|
{$R *.lfm}
|
|
|
|
{ TForm1 }
|
|
|
|
procedure TForm1.FormCreate(Sender: TObject);
|
|
var
|
|
MyThread : TMyThread;
|
|
begin
|
|
MyThread := TMyThread.Create(True); // With the True parameter it doesn't start automatically
|
|
if Assigned(MyThread.FatalException) then
|
|
raise MyThread.FatalException;
|
|
|
|
// Here the code initialises anything required before the threads starts executing
|
|
|
|
MyThread.Start;
|
|
end;
|
|
|
|
{ TMyThread }
|
|
|
|
procedure TMyThread.ShowStatus;
|
|
// this method is only called by Synchronize(@ShowStatus) and therefore
|
|
// executed by the main thread
|
|
// The main thread can access GUI elements, for example Form1.Caption.
|
|
begin
|
|
Form1.Caption := fStatusText;
|
|
end;
|
|
|
|
procedure TMyThread.Execute;
|
|
var
|
|
newStatus : string;
|
|
begin
|
|
fStatusText := 'TMyThread Starting ...';
|
|
Synchronize(@Showstatus);
|
|
fStatusText := 'TMyThread Running ...';
|
|
while (not Terminated) and (true {any condition required}) do begin
|
|
|
|
//here goes the code of the main thread loop
|
|
newStatus:='TMyThread Time: '+FormatDateTime('YYYY-MM-DD HH:NN:SS',Now);
|
|
|
|
if NewStatus <> fStatusText then begin
|
|
fStatusText := newStatus;
|
|
Synchronize(@Showstatus);
|
|
end;
|
|
sleep(50); // alternatively the thread may wait for an event. E.g., external I/O
|
|
end;
|
|
end;
|
|
|
|
constructor TMyThread.Create(CreateSuspended: boolean);
|
|
begin
|
|
FreeOnTerminate := True;
|
|
inherited Create(CreateSuspended);
|
|
end;
|
|
|
|
end.
|
|
|