Delphi How to Use UpArrow DownArrow to navigate

Question

I have a form with a TDBGrid and TClientDatabase.

I want to allow using the UpArrow or DownArrow to navigate in the database no matter which control has focus.

I set the Form.KeyPreview := true

This is the Form.OnKeyPress

procedure TfrmMain.FormKeyPress(Sender: TObject; var Key: Char); 
var Direction : Integer; 
begin    
   Direction := -1;    
   if Key = VK_UP then Direction := 1; {Previous}    
   if Key = VK_DOWN then Direction := 0; {Next}       
   if Direction <> -1 then    
   begin
      if Direction = 0 then cds1.Next else cds1.Prior;
      NextRecord; {Processes AfterScroll event}    
   end; 
end;

This gives me an error E2008 Incompatible types

What am I doing wrong?

Using `FormShortCut` seems to work well: `if ((Msg.CharCode = VK_UP) or (Msg.CharCode = VK_DOWN)) then begin SelectNext(ActiveControl, (Msg.CharCode = VK_DOWN), True); Handled := True; end` — Ron Maupin, Dec 20 '15 at 17:25

MBo · Accepted Answer · 2015-12-20T17:12:23.837

2

Key is Char, but VK_UP is integer constant. You have to use these constants in KeyDown event handler that has parameter Key:Word
Moreover, arrow keys don't generate OnKeyPress event (it is intended for alphanumeric keys)
From help: Navigation keys (Tab, BackTab, the arrow keys, and so on) are unaffected by KeyPreview because they do not generate keyboard events

edited Dec 20 '15 at 17:12

answered Dec 20 '15 at 17:06

MBo

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So not much use with KeyPreview then – David Heffernan Dec 20 '15 at 17:09
This a helpful answer. Thank you MBo. – ChuckO Dec 20 '15 at 17:23
@Chuck To get anywhere you need to follow Sertac's advice in the dupe – David Heffernan Dec 20 '15 at 17:43

Delphi How to Use UpArrow DownArrow to navigate

1 Answers1