CODEWITHSUNDEEP
delphi
Matt Olsen
Matt Olsen

Reputation: 255

detect enter on a memo in Delphi

hi i am doing a command shell using a memo in Delphi , the problem is to detect the last line written and read the command I need to know how to detect the enter key on a memo.

as I can detect the enter key on a memo ?

Upvotes: 2

Views: 7509

Answers (3)

Andreas Rejbrand
Andreas Rejbrand

Reputation: 109002

Detecting the enter key in a TMemo control is easy. Just add an OnKeyPress event:

procedure TForm1.Memo1KeyPress(Sender: TObject; var Key: Char);
begin
  if Key = #13 then
  begin
    // Do something
  end;
end;

Upvotes: 2

Vinatorul
Vinatorul

Reputation: 35

You can use OnKeyDown event, for example:

procedure TForm.Memo1KeyDown(Sender: TObject; var Key: Word;
  Shift: TShiftState);
begin
  if Key = VK_Return then
  begin
    // Your code here ...

    // set Key to 0 if you do not want the key
    // to be default-processed by the control...
    Key := 0 ;
  end;
end;

Upvotes: 3

Deltics
Deltics

Reputation: 23046

In the OnKeypress event you can check for certain keys and handle them as you wish yourself. The enter key is one of these keys.

procedure TForm1.Memo1KeyPress(Sender: TObject; var Key: Char);
const
  ENTER = #13;
begin
  case Key of
    ENTER : begin
              // Do something
            end;
  end;
end;

By default a TMemo has the WantReturns property set to TRUE. This means that as well as any response to the key press that you might implement in your code, the TMemo will still also receive the key event and add a new line to the content of the memo.

If you do not want this then you can either:

  • Set WantReturns = FALSE. you will still get the KeyPress event for the enter key, but the memo will not add new lines in response (they can still be added if the user presses Ctrl + Enter)

OR

  • Keep WantReturns = TRUE but set Key to the value #0 for any key events which you want to suppress (i.e. prevent from reaching the memo control).

An example of this latter approach might look something like this:

const
  NO_KEY = #0;
  ENTER  = #13;
begin
  case Key of
    ENTER : begin
              // Do something

              if NOT AddNewLine then
                Key := NO_KEY;
            end;
  end;
end;

NOTE: The OnKeyPress event only allows you to respond to a subset of key events, specifically those that correspond to CHAR type values (although this does include some non-printing characters such as Tab and Backspace, for example).

If you want or need to detect the state of a wider range of non-character keys or to reliably handle key combinations such as Ctrl+Key or Shift+Key then you will need to query the state of those modifier keys. However, by the time you are responding to the key event, the state of the modifier keys may have changed and a better approach in that case is to use an alternate event which provides a greater range of key events, including the state of the Shift keys (and Control keys) at the time of the key event itself, such as OnKeyDown.

Upvotes: 11

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