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Keyboard Problem

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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Smilly
Asked:
Smilly
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1 Solution
 
MatveyCommented:
Try handling the WM_KILLFOCUS message and returning a non-zero value when the component receives it...
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SmillyAuthor Commented:
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......
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viktornetCommented:
case key of
  VK_LEFT, VK_RIGHT, VK_UP, VK_DOWN : ButtonName.SetFocus;
end;

Merry Chrismas!

-Viktor
--Ivanov
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SmillyAuthor Commented:
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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viktornetCommented:
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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SmillyAuthor Commented:
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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viktornetCommented:
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
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SmillyAuthor Commented:
Hello viktornet, nope, have you tried it, it doesent work....
The event keydown, doesen't check for arrow keys.....

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bruintjeCommented:
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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MatveyCommented:
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
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SmillyAuthor Commented:
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;
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MatveyCommented:
-The component allows it!!! You get the keyboard events, the only diffeerence is that you can't turn the focus away from it.
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SmillyAuthor Commented:
Hello Matvey,
Nope, you can't test for arrow keys on a Tbutton, as
default...
There must be a way to do this.....

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MatveyCommented:
I meant the component I posted - TNoWayOutButton
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SmillyAuthor Commented:
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.......
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MatveyCommented:
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
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SmillyAuthor Commented:
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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MatveyCommented:
Glad we got it at last. All the best wishes for the new year!

Matvey
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