Solved

Keyboard Problem

Posted on 1998-12-23
18
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Last Modified: 2010-04-04
Hi There,
Is there some of you who know, how to snap all keyevents
in a TWinControl.
I am making a editor component of a TWinControl,
and I want to be able to check the keyword.
But when I press the arrow keys, then my control lose
focus. How can I disable this...???
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Comment
Question by:Smilly
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18 Comments
 
LVL 3

Expert Comment

by:Matvey
Comment Utility
Try handling the WM_KILLFOCUS message and returning a non-zero value when the component receives it...
0
 
LVL 1

Author Comment

by:Smilly
Comment Utility
Hello Matvey,
It doesn't work, I have tried this.
Lets say you got a TButton, how will you avoid when
you press the arrow keys, the focus jump to another
control......
0
 
LVL 10

Expert Comment

by:viktornet
Comment Utility
case key of
  VK_LEFT, VK_RIGHT, VK_UP, VK_DOWN : ButtonName.SetFocus;
end;

Merry Chrismas!

-Viktor
--Ivanov
0
 
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Author Comment

by:Smilly
Comment Utility
Nope viktornet, It doesn't help me, it's pretty mush the same as the first answer from Matvey.
But okey, thanks anyway..... I'll make my component based on
EDIT control instead........

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Expert Comment

by:viktornet
Comment Utility
Did u try it at all?? I think that handling the WM_KILLFOCUS message as Matvey mentioned will do exactly what you want without any problems...
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Author Comment

by:Smilly
Comment Utility
Hello Viktornet,
Yes, I have....

procedure TKeyControl.WMKeyDown(var Message: TWMKeyDown);
begin
  case Message.CharCode of
       VK_LEFT, VK_RIGHT, VK_UP, VK_DOWN : caption:='Arrow';
  else
       caption:='None Arrow';
  end;
  inherited;
end;

procedure TKeyControl.WMKillFocus(var Msg: TWMKillFocus);
begin
     inherited;
     setfocus;
     msg.Result := 1;
end;

But I can't test for the arrow keys.
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LVL 10

Expert Comment

by:viktornet
Comment Utility
Ok, you tested the one with WM_KILLFOCUS, but the one that I told you before is not the same as the one that you have tested... Yo should put this code in the OnKeyDown() of the button...

//I don't remember if the parameters were as I put them here, but you got the idea
procedure TForm1.Button1KeyDown(var Key : Word; Sender : TObject);
begin
  case Key of
       VK_LEFT, VK_RIGHT, VK_UP, VK_DOWN : Button1.SetFocus;
  end;
end;

Now this one will work for sure....

-Viktor
--Ivanov
0
 
LVL 1

Author Comment

by:Smilly
Comment Utility
Hello viktornet, nope, have you tried it, it doesent work....
The event keydown, doesen't check for arrow keys.....

0
 
LVL 44

Expert Comment

by:bruintje
Comment Utility
Happy new year everyone.

Strange didn't see it work either, and in the end I did had to override the keydown of TButton.

Found something in the help file

type
  TWMKey = record
    Msg: Cardinal;
    CharCode: Word;
    KeyData: Longint;
    Result: Longint;
  end;

function DoKeyDown(var Message: TWMKey): Boolean;

This is an protected method of TWinControl and as stated there it does the preprocessing of the keydown event.

Hope this helps.
:O) bruintje.

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LVL 3

Expert Comment

by:Matvey
Comment Utility
OK, this works:

___________________________________________________________________________
unit NoWayOutButton;

interface
uses Classes, StdCtrls;

type
  TNoWayOutButton = class(TButton)
  private
    FNoWayOut: Boolean;
  protected
    procedure doExit; override;
  public
    constructor Create(AOwner: TComponent); override;
  published
    property NoWayOut: Boolean read FNoWayOut write FNoWayOut default true;
  end;

procedure Register;

implementation

constructor TNoWayOutButton.Create(AOwner: TComponent);
begin Inherited;
  FNoWayOut := True;
  Width := 100;
end;

procedure TNoWayOutButton.Doexit;
begin
  if FNoWayOut then SetFocus
  else Inherited;
end;

procedure Register;
begin
  RegisterComponents('Samples', [TNoWayOutButton]);
end;

end.
___________________________________________________________________________

Good luck, and a happy new year!
--Matvey
0
 
LVL 1

Author Comment

by:Smilly
Comment Utility
Hello Matvey,
Okey, now you can't get out from the button, but thats
not my Question, my Question is how can I test the arrow
keys inside a button without to lose focus......

Example:

procedure TForm1.Button1KeyDown(Sender: TObject; var Key: Word;
  Shift: TShiftState);
begin
     if (key=VK_LEFT)  then button1.caption:='Left'
     if (key=VK_UP)    then button1.caption:='Up'
     if (key=VK_RIGHT) then button1.caption:='Right'
     if (key=VK_DOWN)  then button1.caption:='Down'
end;
0
 
LVL 3

Expert Comment

by:Matvey
Comment Utility
-The component allows it!!! You get the keyboard events, the only diffeerence is that you can't turn the focus away from it.
0
 
LVL 1

Author Comment

by:Smilly
Comment Utility
Hello Matvey,
Nope, you can't test for arrow keys on a Tbutton, as
default...
There must be a way to do this.....

0
 
LVL 3

Expert Comment

by:Matvey
Comment Utility
I meant the component I posted - TNoWayOutButton
0
 
LVL 1

Author Comment

by:Smilly
Comment Utility
Yes I knew that, but you TNoWayOutButton is made out of a
TButton, and you cant check the arrow keys with it.....
Try it yourself, you cant check the arrow keys, with your
component.......
0
 
LVL 3

Expert Comment

by:Matvey
Comment Utility
Sorry, I really didn't check it. But it's easy to fix:

One way is to use the KeyUp event instead, and another way is to override one method in the TButton by this:

________________________________________________________________
  protected
    procedure WndProc(var Message: TMessage); override;

......................................................

procedure TNoWayOutButton.WndProc(var Message: TMessage);
begin inherited;
 DefaultHandler(Message.Msg);
end;
________________________________________________________________

--Matvey
0
 
LVL 1

Author Comment

by:Smilly
Comment Utility
Thanks Matvey,
That was just what I was seeking for......
But you have to make your comment to a answer,
so you can get your points.......

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Accepted Solution

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Matvey earned 20 total points
Comment Utility
Glad we got it at last. All the best wishes for the new year!

Matvey
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