changing focus on a form
lazarus / 1-Linux

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bayparinc · 2009-06-23 04:06

Hi to all,

I have this scenario, a Form with a 3 TEdit, TMemo, 2 TButtons and 1
TBitbtn.  When the form is   displayed, the input focus is setting on
edit box 1. What I want to do is put a code on the event of tbitbtn to
change the focus from one control to the other, as if i have pressed
the tab key from the keyboard.  I have use    
  SelectNext(Sender as TWinControl, True, True );  // but doesn't do
the job
have tried also
  PerformTab( True );  //but does not work either
also DoKeyPress( VK_Tab );  doesn't work also

Is their any other solution that i can i try?  Many thanks

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Vincent Snijders · 2009-06-23 09:03

Why do you pass the sender to SelectNext? Is the control you want to
select then next in the taborder after the clicked bitbtn? If not,
SelectNext(ActiveControl,true, true); may work better.

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bayparinc · 2009-06-24 01:14

yes, i want to pass the control to next taborder after the clicked on
bitbtn, better solution if it will work for other keys also.

I have tried SelectNext( ActiveControl, true, true); but doesn't do
the job too. 

procedure TForm1.BitBtn1Click(Sender: TObject);
begin
    SelectNext( ActiveControl, true, true );  // this one jumps into
one of the control but not the next      taborder on the first clicked
only

   //SelectNext(Sender as TWinControl, True, True );  // but doesn't
do the job
   //PerformTab( True );  //but does not work either
   //DoKeyPress( VK_Tab );  doesn't work also

end;

I'm trying the postmessage that works with delphi but doesn't compile
in lazarus maybe because it's not a cross platform.

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clauslack · 2009-06-24 02:25

ENTER key simulates TAB key betwen TEdit controls. You can adapt this
to your needs.
Code: [Select]Form1.KeyPreview:=true;

Code: [Select]procedure TForm1.FormKeyPress(Sender: TObject; var Key:
char);
begin
   if key=#13 then
   if (ActiveControl is TEdit) then
   begin
        key:=#0;
        SelectNext(ActiveControl,true, true);
    end;
end;          

Regards

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bayparinc · 2009-06-24 02:58

the application that i'm writing is actually a touch screen,
possibility that there will be no keyboard.  So i'm attempting to
mimic a tab or enter key after clicking the bitbtn. 

SelectNext(ActiveControl, true, true); works fine using keyboard.

Thanks for the help.

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bayparinc · 2009-06-26 02:02

I'm still looking for a way in which i can force my program to drive a
keypress using buttons.  I'm doing a program with a numeric tbuttons
and 3 tedit boxes, a tab button and esc button in form.  If any of the
numeric buttons is pressed, it will be an input to the tedit box
depending on the focus.  Tab button will move the focus on the next
tedit, while esc button will close the form.  Initial focus will be
tedit1 when the form show.

I'm thinking that if my user click those buttons it will push a
keypress to the keyboard buffer so that it can be trap using the 
keypreview := true and keypress which will be much easier to trap.

Upto now i don't have a lack of solving it:-( Any suggestions will be
much appreciated. Thanks again.

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Leledumbo · 2009-06-26 07:37

QuoteI'm still looking for a way in which i can force my program to
drive a keypress using buttons.You can call OnKeyPress from button's
OnClick, for instance:
Code: [Select]procedure TForm1.Button1Click(Sender: TObject);
var
  c: Char = #13;
begin
  Form1KeyPress(Sender,c); // send enter key
end;

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bayparinc · 2009-06-26 10:49

Quote from: Leledumbo on June 26, 2009, 09:37:03 amQuoteI'm still
looking for a way in which i can force my program to drive a keypress
using buttons.You can call OnKeyPress from button's OnClick, for
instance:
Code: [Select]procedure TForm1.Button1Click(Sender: TObject);
var
  c: Char = #13;
begin
  Form1KeyPress(Sender,c); // send enter key
end;

Thanks Leledumbo,
   Form1.KeyPress( c ); works:-)

But i face another challenge, i need the focus to stay on my edit box
when clicking buttons. I think the focus is given on the clicked
button, so the KeyPress which is passed by the onclick event is not
processed/loss.

Hope someone had work on this before.

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Leledumbo · 2009-06-26 11:57

QuoteBut i face another challenge, i need the focus to stay on my edit
box when clicking buttons.Add
Code: [Select]Edit1.SetFocus; // or any of the TEdit
somewhere in the button's OnClick.

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bayparinc · 2009-06-29 01:10

Thanks again leledumbo for your prompt reply.

Sorry, this one is i think a basic in programming, but it seems i
don't know how to make it.  Basically the keypress are not posted on
the edit entry, another thing is how to know where is the focus entry?

Thanks for your tips, it is much appreciated.

Code: [Select]unit Unit1;

{$mode objfpc}{$H+}

interface

uses
  Classes, SysUtils, FileUtil, LResources, Forms, Controls, Graphics,
Dialogs,
  StdCtrls, Buttons;

type

  { TForm1 }

  TForm1 = class(TForm)
    btn2: TBitBtn;
    btn3: TBitBtn;
    btnEnter: TBitBtn;
    btnTab: TBitBtn;
    btnEsc: TBitBtn;
    btn1: TBitBtn;
    Edit1: TEdit;
    Edit2: TEdit;
    Edit3: TEdit;
    procedure btn1Click(Sender: TObject);
    procedure btn2Click(Sender: TObject);
    procedure btn3Click(Sender: TObject);
    procedure btnTabClick(Sender: TObject);
    procedure btnEscClick(Sender: TObject);
    procedure FormKeyPress(Sender: TObject; var Key: char);
    procedure FormShow(Sender: TObject);
  private
    { private declarations }
  public
    { public declarations }
  end;


var
  Form1: TForm1;

implementation

{ TForm1 }

procedure TForm1.btn1Click(Sender: TObject);
var c:char;
begin
  c:= '1';

  Edit1.SetFocus;       //currently hardcoded to be in edit1;
enhancement is to know who has the focus when a keypress is done

  Form1.Keypress(c);    // it doesn't work, it does not post the char
in my edit box ;-(

end;

procedure TForm1.btn2Click(Sender: TObject);
var c:char;
begin
  c:= '2';

  Edit1.SetFocus;         //currently hardcoded to be in edit1;
enhancement is to know who has the focus when a keypress is done
  Form1.Keypress(c);    // it doesn't work, it does not post the char
in my edit box ;-(

end;

procedure TForm1.btn3Click(Sender: TObject);
var c:char;
begin
  c:= '3';

  Edit1.SetFocus;     //currently hardcoded to be in edit1;
enhancement is to know who has the focus when a keypress is done

  Form1.Keypress(c);     // it doesn't work, it does not post the char
in my edit box ;-(

end;

procedure TForm1.btnTabClick(Sender: TObject);
var c:char;
begin

  c:=chr(9);               // should simulate a tab key
  Form1.Keypress(c);       //

end;

procedure TForm1.btnEscClick(Sender: TObject);
var c:char;
begin

  c:=#27;
  Form1.Keypress(c);              // this one work; the form close

end;

procedure TForm1.FormKeyPress(Sender: TObject; var Key: char);
begin

  if Key = #27 then close ;
  ShowMessage('Key=' + Key);   // shows correct as specified on my
keypress; but the key is not posted on the edit box

end;

procedure TForm1.FormShow(Sender: TObject);
begin
  Edit1.SetFocus;

end;

initialization
  {$I unit1.lrs}

end.

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Leledumbo · 2009-06-29 09:16

QuoteBasically the keypress are not posted on the edit entryWell...
that's because you're calling the form's OnKeyPress instead of the
edit's one. You can try the following code (untested):
Code: [Select]procedure TForm1.Btn1Click(Sender: TObject);
var
  c: Char;
begin
  c:='1';
  Edit1.OnKeyPress(Edit1,c);
end;

procedure TForm1.Btn2Click(Sender: TObject);
var
  c: Char;
begin
  c:='2';
  Edit1.OnKeyPress(Edit1,c);
end;

procedure TForm1.Btn3Click(Sender: TObject);
var
  c: Char;
begin
  c:='3';
  Edit1.OnKeyPress(Edit1,c);
end;
Quoteanother thing is how to know where is the focus entry?You can get
it from ActiveControl property.

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bayparinc · 2009-06-30 00:26

the code also failed, it gives me "External: SIGSEGV" and exception
error "RunError(216)".

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Leledumbo · 2009-06-30 09:58

Quotethe code also failed, it gives me "External: SIGSEGV" and
exception error "RunError(216)"OK, I thought I did it wrong, the
Edit's OnKeyPress must be nil because it's not set. That's the cause
of GPF (i.e. RTE 216). Try this (still untested):
Code: [Select]procedure TForm1.Btn1Click(Sender: TObject);
begin
  if ActiveControl is TEdit then
    ActiveControl.Text:=ActiveControl.Text+'1';
end;

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bayparinc · 2009-07-01 00:19

I got error during complilation, cause the text is not a property of
active control
["identifier indents no member "text"]

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Vincent Snijders · 2009-07-01 06:44

I guess Leledumbo meant:
Code:
[Select]TEdit(ActiveControl).Text:=TEdit(ActiveControl).Text+'1';

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bayparinc · 2009-07-01 06:58

I was able to solve the issue by converting the sendkey32.pas which
work in delphi.  My issue now is when i compile in linux, it looks for
windows.pp.  Does that mean my program only works for windows? Or is
there a cross platform windows.pp equivalent?

Thanks for your patience, leledumbo and vincent:-)

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Vincent Snijders · 2009-07-01 07:04

There is no cross platform equivalent for windows.pp.

Some functions in the windows unit can be found in the lclintf unit.

As a cross platform alternative of the sendkey32 unit, you may want to
look at http://wiki.lazarus.freepascal.org/MouseAndKeyInput

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bayparinc · 2009-07-01 07:15

Thanks vincent, i'll give it a try.

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Leledumbo · 2009-07-01 08:00

QuoteI guess Leledumbo meant:Whoops! Forgot the casts, thanks Vincent
(I was thinking of using as operator actually).

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Vincent Snijders · 2009-07-01 09:06

If you just tested with "is", using "as" is a waste of resources,
IMHO.