[SOLVED] Problem accessing GUI element from Thread on Modal form

[mudah]

Hello

I need some help here. I have created Child Form as modal and now having problem accessing GUI element from within TMyThread.ShowStatus. Below is the complete code..

Parent form

Code: [Select]

unit uParent;

{$mode objfpc}{$H+}

interface

uses
  Classes, SysUtils, FileUtil, Forms, Controls, Graphics, Dialogs, StdCtrls,
  uChild;

type

  { TfParent }

  TfParent = class(TForm)
      Button1: TButton;
      procedure Button1Click(Sender: TObject);
  private
    { private declarations }
  public
    { public declarations }
  end;

var
  fParent: TfParent;

implementation

{$R *.lfm}

{ TfParent }

procedure TfParent.Button1Click(Sender: TObject);
var
    OpenChild: TfChild;
begin
    OpenChild:= TfChild.Create(nil);
    OpenChild.ShowModal;
    ShowMessage('Child Closed');
end;

end.
Child Form

Code: [Select]

unit uChild;

{$mode objfpc}{$H+}

interface

uses
  Classes, SysUtils, Forms, StdCtrls;

type

  { TMyThread }

  TMyThread = class(TThread)
  private
    fStatusText: string;
    procedure ShowStatus;
  protected
    procedure Execute; override;
  public
    constructor Create(CreateSuspended: boolean);
  end;

  TfChild = class(TForm)
      Button1: TButton;
      Label1: TLabel;
      procedure Button1Click(Sender: TObject);
  private
    { private declarations }
  public
    { public declarations }
  end;


var
  fChild: TfChild;

implementation

{$R *.lfm}

{ TfChild }

procedure TfChild.Button1Click(Sender: TObject);
var
      MyThread : TMyThread;
 begin
      MyThread := TMyThread.Create(True);
      MyThread.Resume;
 end;

procedure TMyThread.ShowStatus;
begin
    fChild.Caption := fStatusText; //<---- problem here!

end;

procedure TMyThread.Execute;
begin
fStatusText := 'Starting';
    Synchronize(@Showstatus);
end;

constructor TMyThread.Create(CreateSuspended: boolean);
begin
  FreeOnTerminate := True;
  inherited Create(CreateSuspended);
end;
end.

Herewith attached source code. Can someone help me please

Thanks a bunch!

-- WinXP SP3
-- Lazarus 0.9.30.1 - 31909
-- FPC 2.4.2

[Blaazen]

Man, I'll kill you. 

I was thinking so long and it was in front of my eyes.

Of course, you must have openChild:

Code: [Select]

procedure TMyThread.ShowStatus;
begin
   openChild.Caption := fStatusText;

end;

because openchild is created when you press fParent.button1 .
And, of course, you must move openchild to global variables.
Or, create (or swohmodal)  fChild, when fParent.Button1 click.

(Note: I didn't use your original project; I only copy/pasted the code, so I don't know if your fChild is autocreated or not)

EDIT: Resume seems be deprecated. See here: http://wiki.freepascal.org/User_Changes_2.4.4#TThread.Suspend_and_TThread.Resume_have_been_deprecated

[mudah]

Global variable.. rite.  I commit suicide now..

Problem solved by moving openChild to global variable.



Thanks a bunch Blaazen!

[Blaazen]

I forgot one think:

Code: [Select]

procedure TfParent.Button1Click(Sender: TObject);
begin
    OpenChild:= TfChild.Create(nil);
    OpenChild.ShowModal;
    ShowMessage('Child Closed');
    OpenChild.Free;  // <--- HERE
end;

You should can Free to avoid memory leaks.

[mudah]

+1

Thanks again Blaazen!

[TheProgrammer]

http://lazarus.freepascal.org/index.php/topic,14321.msg75754.html#msg75754

do not forget that which you create you must also destroy

Ok I write Destroy/destructor code...
Oké Írok lezáró részeket (Destroy)...