How can I read barcodes without having the user focus a text box first?

Question

I recently acquired a Metrologic Barcode scanner (USB port), as everyone already knows it works as a keyboard emulator out of the box.

How do I configure the scanner and

Answer 1

You can use the OnShortcut event on a form to intercept keyboard presses. Check if the prefix you configured on the barcodescanner appears, and set as Handled al keypresses until you get the barcode scanner suffix. Within your Shortcut handler build up the barcode string

The following code is adapted from something I use myself, but is untested in its current form.

    // Variables defined on Form object
GettingBarcode : boolean;
CurrentBarcode : string;
TypedInShiftState: integer; // 16=shift, 17=ctrl, 18=alt

procedure Form1.FormShortCut(var Msg: TWMKey; var Handled: Boolean);
var
  Character:Char;
begin
  Character:=Chr(MapVirtualKey(Msg.CharCode,MAPVK_VK_TO_CHAR));
  if GettingBarcode then
  begin
    // Take care of case 
    if (TypedInShiftState<>16) and CharInSet(Character,['A'..'Z']) then
        Character:=Chr(Ord(Character)+32);
    TypedInShiftState:=0;
    // Tab and Enter programmed as suffix on barcode scanner
    if CharInSet(Character,[#9, #13]) then
    begin
      // Do something with your barcode string
      try
        HandleBarcode(CurrentBarcode);
      finally
        CurrentBarcode:='';
        Handled:=true;
        GettingBarcode:=False;
      end;
    end
    else if CharInSet(Character,[#0..#31]) then
    begin
      TypedInShiftState:=Msg.CharCode;
      Handled:=True;
    end
    else begin
      CurrentBarcode:=CurrentBarcode+Character;
      Handled:=true;
    end;
  end
  else begin
    if Character=#0 then
    begin
      TypedInShiftState:=Msg.CharCode;
    end
    else if (TypedInShiftState=18) and (Character='A') then
    begin
      GettingBarcode:=True;
      CurrentBarcode:='';
      Handled:=true;
    end;
  end;
end;