Title: Drag Drop from Stringgrid to Listbox
Question: How to drag a whole column from a StringGrid to a Listbox.
Answer:
Drop a Listbox and a StringGrid on the Form.
Set the dragmode property of the StringGrid to dmAutomatic in the object inspector.
Listbox Events :
OnDragOver - Accept:=Source is TStringGrid;
This so the Listbox would accept only data from a TStringGrid.
OnDragDrop -
procedure TForm1.ListBox1DragDrop(Sender, Source: TObject; X, Y: Integer);
var
i : integer;
ColumVal,CurrentCol : Integer;
begin
if Source is TStringGrid then
begin
//Calculate in which column we are.
ColumVal:=0;
CurrentCol:=0;
for i:=0 to TStringGrid(Source).ColCount-1 do
begin
ColumVal:=ColumVal+TStringGrid(Source).ColWidths[i];
if XMouseCord begin
CurrentCol:=i;
break;
end;
end;
//Make sure we are not in the first column which has no data
if CurrentCol0 then
begin
for i:=1 to TStringGrid(Source).RowCount-1 do
begin
ListBox1.items.Add(TStringGrid(Source).Cells[CurrentCol,i]);
end;
end;
StartDrag:=True;
end;
end;
First we see if the source is from a StringGrid. Then we need to calculate from which column on the Stringgrid it comes from using the mouse coordinate. (This take in account that every column is a different size.) If the column isn't the first one ,which usually have no data, then we put the whole column, one row at a time into the Listbox.
StringGrid Events :
OnDragOver -
if StartDrag then
begin
XMouseCord := X;
StartDrag:=False;
end;
TheStartDrag is a Boolean to stop the event from recording every mouse x coordinate after dragging started.
OnDragOver - StartDrag:=True;
This is so in the case we drop it on the StringGrid and not the Listbox.
Here is the entire source for it to work.
type
TForm1 = class(TForm)
StringGrid1: TStringGrid;
ListBox1: TListBox;
procedure ListBox1DragOver(Sender, Source: TObject; X, Y: Integer;
State: TDragState; var Accept: Boolean);
procedure ListBox1DragDrop(Sender, Source: TObject; X, Y: Integer);
procedure FormCreate(Sender: TObject);
procedure StringGrid1DragOver(Sender, Source: TObject; X, Y: Integer;
State: TDragState; var Accept: Boolean);
procedure StringGrid1DragDrop(Sender, Source: TObject; X, Y: Integer);
private
{ Private declarations }
XMouseCord : Integer;
StartDrag : Boolean;
public
{ Public declarations }
end;
var
Form1: TForm1;
implementation
{$R *.DFM}
procedure TForm1.ListBox1DragOver(Sender, Source: TObject; X, Y: Integer;
State: TDragState; var Accept: Boolean);
begin
Accept:=Source is TStringGrid;
end;
procedure TForm1.ListBox1DragDrop(Sender, Source: TObject; X, Y: Integer);
var
i : integer;
ColumVal,CurrentCol : Integer;
begin
if Source is TStringGrid then
begin
//Calculate in which column we are.
ColumVal:=0;
CurrentCol:=0;
for i:=0 to TStringGrid(Source).ColCount-1 do
begin
ColumVal:=ColumVal+TStringGrid(Source).ColWidths[i];
if XMouseCord begin
CurrentCol:=i;
break;
end;
end;
//Make sure we are not in the first column which has no data
if CurrentCol0 then
begin
for i:=1 to TStringGrid(Source).RowCount-1 do
begin
ListBox1.items.Add(TStringGrid(Source).Cells[CurrentCol,i]);
end;
end;
StartDrag:=True;
end;
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
//For Demo purpose
with StringGrid1 do
begin
Cells[1,1]:='T1';
Cells[1,2]:='T2';
Cells[1,3]:='T3';
Cells[1,4]:='T4';
Cells[2,1]:='T5';
Cells[2,2]:='T6';
Cells[2,3]:='T7';
Cells[2,4]:='T8';
Cells[3,1]:='T9';
Cells[3,2]:='T10';
Cells[3,3]:='T11';
Cells[3,4]:='T12';
Cells[4,1]:='T13';
Cells[4,2]:='T14';
Cells[4,3]:='T15';
Cells[4,4]:='T16';
end;
StartDrag:=True;
end;
procedure TForm1.StringGrid1DragOver(Sender, Source: TObject; X,
Y: Integer; State: TDragState; var Accept: Boolean);
begin
//Store which column we are on when the dragging started.
if StartDrag then
begin
XMouseCord := X;
StartDrag:=False;
end;
end;
procedure TForm1.StringGrid1DragDrop(Sender, Source: TObject; X,
Y: Integer);
begin
//Just in case we drop it on the grid
StartDrag:=True;
end;
This was my first tutorial, so I hope it helps someone.