Key Word vs Key Char

[Petrus Vorster]

Last question for a while gents.

This is where the beginner doesnt understand.

I want to limit the user from capturing anything else but NUMBERS in a Tcombobox.
From my reading, that must be done in the KEYDOWN event and not the Keypress like in the case of a Tedit control.

The Keydown event :

Code: Pascal  [Select][+][-]

1. procedure TForm1.ComboBox4KeyDown(Sender: TObject; var Key: Word;
2.   Shift: TShiftState);  

VS

The Keypress event:

Code: Pascal  [Select][+][-]

1. procedure TForm1.ComboBox4KeyPress(Sender: TObject; var Key: char);

In the first line the KEY : Word and the second one Key:Char.
I know how to limit the text input using the CHar :

Code: Pascal  [Select][+][-]

1. if not (Key in ['0'..'9', '.', #8, #9]) then Key := #0;

I still need to learn how to adapt that to work with the first (keydown) event.

If someone can show me please.


-Peter

[Petrus Vorster]

Code: Pascal  [Select][+][-]

1.  if not (Key in [8..9, 96..105]) then Key := 0;  

Thanks great people.

-Peter

[paweld]

Code: Pascal  [Select][+][-]

1. if not (Key in [48..57, VK_OEM_PERIOD, VK_BACK, VK_TAB]) then Key := 0; //48: VK_0, 57: VK_9

  more codes find in LCLType unit 
   
Edit: The key codes that @Petrus Vorster provided only work when NumLock is pressed.

[Bart]

I know how to limit the text input using the CHar :

Code: Pascal  [Select][+][-]

1. if not (Key in ['0'..'9', '.', #8, #9]) then Key := #0;

I still need to learn how to adapt that to work with the first (keydown) event.

For what you are doing here, OnKeyPress is the right place.
Notice that a give char can be generated using different Keys (e.g. I can type a capital A using ALT+0+0+6+5, which gives multiple OnKeyDowns, but 1 OnKeyPress), and if you are only interested in what char was eventually generated, use OnKeyPress.
If you want to e.g. react on the Left or Right arrow key (or any other function key) or need to know wether or not Shift/Ctrl/Alt is pressed, you need to use the OnKeyDown, since that cannot be done in OnKeyPress.

Bart

[paweld]

For what you are doing here, OnKeyPress is the right place.
Notice that a give char can be generated using different Keys (e.g. I can type a capital A using ALT+0+0+6+5, which gives multiple OnKeyDowns, but 1 OnKeyPress), and if you are only interested in what char was eventually generated, use OnKeyPress.

But, if your codepage is another than cp1252 then use OnUtf8KeyPress event.

[Bart]

But, if your codepage is another than cp1252 then use OnUtf8KeyPress event.

You should use that whenever you want to control any "character" that's not lower ascii, regardless of your (windows) codepage.

Bart