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how to handle postmessage in TThread Objects

Posted on 2001-07-18
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Last Modified: 2012-05-04
I have a TThread object and desire to execute within a Postmessage, but so that reason does not execute????? Greetings
Ruben  
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Comment
Question by:rbarzallo
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18 Comments
 
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Expert Comment

by:bnemmers
Comment Utility
Try PostThreadMessage

Bill
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Expert Comment

by:comptebidon81
Comment Utility
If I understood right, you want to start your thread when you receive a PostMessage?

Doing something like this when you receive the PostMessage should start it:
MyThread := TMyThread.Create(False);

If that is already what you did or I didn't understood correctly your question, don't hesitate to tell me!
GunDamn
0
 

Author Comment

by:rbarzallo
Comment Utility
ok,
thread this in execution and within this execution desire to execute postmessage, thread executes the instruction but not the procedure assigned to the same one (to postmessage). The same it happens to me with postthreadmessage.

Ruben  
 
0
 

Expert Comment

by:comptebidon81
Comment Utility
Are you posting your message with the right window handle?
I suppose you wish to post a message outSide of the Thread?
If not, maybe you could try to put your PostMessage procedure outside your thread.

If it still doesn't work, I will need a code sample to help you further.
GunDamn
0
 

Expert Comment

by:SMakarenko
Comment Utility
it may do in the following way :

   TRunThread =class(TThread)
   protected
   private
     FWindowHandle: HWND;
     procedure WndProc(var Msg: TMessage);
     procedure DoAnything;
   public
     procedure Execute;override;
   end;
 
procedure TRunThread.Execute;
begin
  FWindowHandle := AllocateHWnd(WndProc);
  DoSomething;
  DeallocateHWnd(FWindowHandle);
end;


procedure TRunThread.DoAnything;
begin
 ...
end;

procedure TRunThread.WndProc(var Msg: TMessage);
begin
  with Msg do
    if Msg = WM_Thread then
      try
        DoAnything;
      except
        Application.HandleException(Self);
      end
    else
      Result := DefWindowProc(FWindowHandle, Msg, wParam, lParam);
end;

 
0
 

Expert Comment

by:SMakarenko
Comment Utility
in execute  add next text:

  while GetMessage(Msg,0, 0, 0) do
  begin
    TranslateMessage(Msg);
    DispatchMessage(Msg);
  end;



and remove procedure DoSomething;
0
 

Expert Comment

by:SMakarenko
Comment Utility
in execute  add next text:

  while GetMessage(Msg,0, 0, 0) do
  begin
    TranslateMessage(Msg);
    DispatchMessage(Msg);
  end;



and remove procedure DoSomething;
0
 

Author Comment

by:rbarzallo
Comment Utility

why not postmessage not processing wmcontrolclose???????

unit pruebas;

interface

uses
  Messages, Forms, Classes, SysUtils,Windows, Dialogs;

const
  wm_Controlclose = WM_User + 1;

type
  ThSwt_Input = class(TThread)
 
  public

    constructor Create(CreateSuspended: Boolean);
    procedure   WmControlclose(var Msg: TMessage); Message wm_ControlClose;

             
  private
    { Private declarations }
    //
  protected
    procedure Execute; override;
    procedure ProceseMessage;
                                 
  end;

var
  ThSwitch_In     : ThSwt_Input;

implementation

{ Important: Methods and properties of objects in VCL can only be used in a
  method called using Synchronize, for example,

      Synchronize(UpdateCaption);

  and UpdateCaption could look like,

    procedure THDataQueueInput.UpdateCaption;
    begin
      Form1.Caption := 'Updated in a thread';
    end; }

{ THDataQueueInput }

constructor ThSwt_Input.Create(CreateSuspended: Boolean);
begin
   Inherited Create(CreateSuspended);
end;

procedure ThSwt_Input.Execute;
begin

  { Place thread code here }
ProceseMessage;
   
end;

procedure ThSwt_Input.ProceseMessage;
var
s1 : string;
begin

  PostMessage(Handle,wm_Controlclose ,0,0);

  s1 := 'continuo con la ejecucion del programa';
  showmessage(s1);
 
  // mas codigo del programa

end;

procedure ThSwt_Input.WmControlclose(var Msg: TMessage);
var
s1 : string;
begin
  // realiza proceso interno
  s1 := 'ejecuta postmessage';
  showmessage(s1);
end;                          

end.
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Author Comment

by:rbarzallo
Comment Utility

why postmessage not processing wmcontrolclose???????

unit pruebas;

interface

uses
  Messages, Forms, Classes, SysUtils,Windows, Dialogs;

const
  wm_Controlclose = WM_User + 1;

type
  ThSwt_Input = class(TThread)
 
  public

    constructor Create(CreateSuspended: Boolean);
    procedure   WmControlclose(var Msg: TMessage); Message wm_ControlClose;

             
  private
    { Private declarations }
    //
  protected
    procedure Execute; override;
    procedure ProceseMessage;
                                 
  end;

var
  ThSwitch_In     : ThSwt_Input;

implementation

{ Important: Methods and properties of objects in VCL can only be used in a
  method called using Synchronize, for example,

      Synchronize(UpdateCaption);

  and UpdateCaption could look like,

    procedure THDataQueueInput.UpdateCaption;
    begin
      Form1.Caption := 'Updated in a thread';
    end; }

{ THDataQueueInput }

constructor ThSwt_Input.Create(CreateSuspended: Boolean);
begin
   Inherited Create(CreateSuspended);
end;

procedure ThSwt_Input.Execute;
begin

  { Place thread code here }
ProceseMessage;
   
end;

procedure ThSwt_Input.ProceseMessage;
var
s1 : string;
begin

  PostMessage(Handle,wm_Controlclose ,0,0);

  s1 := 'continuo con la ejecucion del programa';
  showmessage(s1);
 
  // mas codigo del programa

end;

procedure ThSwt_Input.WmControlclose(var Msg: TMessage);
var
s1 : string;
begin
  // realiza proceso interno
  s1 := 'ejecuta postmessage';
  showmessage(s1);
end;                          

end.
0
 

Expert Comment

by:SMakarenko
Comment Utility
you must create Window in Thread and MessageQueue

  like in my text

FWindowHandle := AllocateHWnd(WndProc);



 

 
0
 

Expert Comment

by:SMakarenko
Comment Utility
procedure ThSwt_Input.Execute;
begin
  FWindowHandle := AllocateHWnd(WndProc);
  while GetMessage(Msg,0, 0, 0) do
  begin
    TranslateMessage(Msg);
    DispatchMessage(Msg);
  end;
  DeallocateHWnd(FWindowHandle);
end;



you may postmessage  out From Thread

var
  Thread:ThSwt_Input;

 
procedure TForm1.Button1Click(Sender: TObject);
begin
  Thread := ThSwt_Input.Create(True);
  IsTread:=True;
  Thread.OnTerminate := ThreadTerminate;
  Thread.FreeOnTerminate := True;
  Thread.Resume;
end;


procedure TForm1.Button2Click(Sender: TObject);
begin
  SendMessage(Thread.FWindowHandle, WM_USER + 1, 0, 0);
end;




procedure ThSwt_Input.ProceseMessage;
begin
 Synchronize(DoAnything);
end;




procedure ThSwt_Input.DoAnything;
var
s1 : string;
begin
 s1 := 'ejecuta postmessage';
 showmessage(s1);
end;
0
 

Accepted Solution

by:
SMakarenko earned 15 total points
Comment Utility
procedure ThSwt_Input.WndProc(var Msg: TMessage);
begin
  with Msg do
    if Msg = wm_Controlclose then
      try
        ProceseMessage;
      except
        Application.HandleException(Self);
      end
    else
      Result := DefWindowProc(FWindowHandle, Msg, wParam, lParam);
end;
0
 
LVL 2

Expert Comment

by:alexstewart@beta
Comment Utility
Not wishing to muddy the waters, but you might also look
at the api PostThreadMessage,

Iuse it for talking to threads, you dont need a window handle.

as
0
 
LVL 2

Expert Comment

by:alexstewart@beta
Comment Utility
oops sorry Bill, you said that.
Any way I do the following..

procedure TMyThread.Execute;
var
   Msg : TMsg;
begin
  PeekMessage(msg, 0, WM_USER, WM_USER, PM_NOREMOVE);// start the thread message queue
  MyThreadId:=ThreadID;// stick the thread id somewhere I can find it.
  MyStartup;
  while True do begin
      if Terminated then Break;//check if anyone called mythread.terminate-
      IF NOT GetMessage(Msg, 0, 0, 0) THEN Break;//could peak here to prevent stall, this returns false if WM_Quit is posted
      MyProcessMsg(msg);//I process the message
      end;
  MyCleanup;
end;

In the main program I call
PostThreadMessage(MyThreadId,wm_xxx,0,0);
0
 

Expert Comment

by:SMakarenko
Comment Utility
agree
its work :)


rbarzallo wants
postmessage  inner Thread
 
 
0
 

Expert Comment

by:Jgould
Comment Utility
Dear SMakarenko


I've rejected your proposed answer as Experts Exchange holds an experiment to work without the answer button.

See:        http://www.experts-exchange.com/jsp/communityNews.jsp
Paragraph: Site Update for Wednesday, November 06, 2002

By this rejection the Asker will be notified by mail and hopefully he will take his responsibility to finalize the question or post an additional comment.
The Asker sees a button beside every post which says "Accept This Comment As Answer" (including rejected answers) -- so if he/she thinks yours is the best, you'll be awarded the points and the grade.

This Q hasn't been active lately, thus I've posted it in the CS Cleanup topic area.
I'll return to this Q in seven days to see if any coment has been added, if not then it's my intention that this question is:

-Answered by: SMakarenko

PLEASE DO NOT ACCEPT THIS COMMENT AS AN ANSWER !

Thanks !

Jgould

Community Support Moderator
Experts Exchange
0
 
LVL 26

Expert Comment

by:Russell Libby
Comment Utility
No comment has been added lately, so it's time to clean up this TA.
I will leave a recommendation in the Cleanup topic area that this question is:

Accept SMakarenko's comment as answer
(will be submitted on 06/18/2003 to cleanup)

Please leave any comments here within the next seven days.
 
PLEASE DO NOT ACCEPT THIS COMMENT AS AN ANSWER!
 
Thank you,
Russell

EE Cleanup Volunteer
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