key down

From Free Pascal wiki
Revision as of 13:50, 13 December 2017 by Paskal (talk | contribs) (→‎Overview)
Jump to navigationJump to search

Deutsch (de) English (en)

Overview

The OnKeyDown event of an object allows you to check what key the user has pressed.

Note that the procedure keeps track of shift/alt/ctrl etc keys separately (in Shift) from the "regular" keys (in Key) - see the procedure signature in the example.

Light bulb  Note: OnKeyDown doesn't support Unicode characters. If you need Unicode characters but no control characters, use OnUTF8KeyPress.

{{Note|When a key is hold down the OnKeyDown event is re-triggered. The first re-triggering event is after approx 500 ms and the next ones cycle between 30 and 50 ms.

Example

uses
  ...LCLType, Dialogs, ...;
  ...  
procedure TForm1.Edit1KeyDown(Sender: TObject; var Key: Word;
  Shift: TShiftState);
begin
  // Example: checking for simple keys:
  if (Key = VK_DOWN) or
     (Key = VK_UP) then
    ShowMessage('Pressed arrow up or down key');
  // Check for Alt-F2
  if (Key = VK_F2) and (ssAlt in Shift) then
    ShowMessage('Alt F2 was pressed')
end;

See also