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OnMouseDown/dragdrop for TDBGrid

Posted on 2001-09-10
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Last Modified: 2008-03-17
Hi, I'm trying to initiate drag & drop from a DBgrid but I want to do it manually so it does not interfere with normal cell editing/selection.  I normally use the OnMouseDown event to capture drag-drop but this only seems to get fired on the DBGrid for the row-headers!  Does anyone please know how can I get the desired drag-drop effect?  Thx.
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Question by:Mangolab
3 Comments
 
LVL 27

Accepted Solution

by:
kretzschmar earned 400 total points
ID: 6471394
maybe this gives you a hint,

a sample for resorting grid entries with drag&drop

unit dbg_dd_u;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  Grids, DBGrids, Db, DBTables;

type
  TForm1 = class(TForm)
    Table1: TTable;
    DataSource1: TDataSource;
    DBGrid1: TDBGrid;
    procedure DBGrid1MouseMove(Sender: TObject; Shift: TShiftState; X,
      Y: Integer);
    procedure DBGrid1DragOver(Sender, Source: TObject; X, Y: Integer;
      State: TDragState; var Accept: Boolean);
    procedure FormCreate(Sender: TObject);
    procedure DBGrid1MouseUp(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure DBGrid1DragDrop(Sender, Source: TObject; X, Y: Integer);
  private
    InDrag : Boolean;
    RowIndex : Integer;
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.DFM}

procedure TForm1.DBGrid1MouseMove(Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
Var GridCoord : TGridCoord;
begin
  if (ssleft in shift) and not InDrag then
  begin
    GridCoord := DBgrid1.MouseCoord(x,y);
    if GridCoord.y > -1 then  //am i on a record
    begin
      RowIndex := GridCoord.y; //Remember the row
      DBGrid1.BeginDrag(False,5);  //begin in 5 additional pixelsmoves
      InDrag := True; //Now Dragging
    end;
  end;

end;

procedure TForm1.DBGrid1DragOver(Sender, Source: TObject; X, Y: Integer;
  State: TDragState; var Accept: Boolean);
Var GridCoord : TGridCoord;
begin
  GridCoord := DBgrid1.MouseCoord(x,y);
  Accept := (Sender = Source) and    //Accept only if the mouse
            (GridCoord.y > -1) and   //points to another record
            (GridCoord.y <> RowIndex)
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  InDrag := False;  //Dragging done
end;

procedure TForm1.DBGrid1MouseUp(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  InDrag := False;  //Dragging done
end;

procedure TForm1.DBGrid1DragDrop(Sender, Source: TObject; X, Y: Integer);
Var
  GridCoord : TGridCoord;
  BMSource, BMDest : TBookmark;
  DestPos, SourcePos : Integer;
begin
  Table1.DisableControls;                   //Don't Show the action
  GridCoord := DBgrid1.MouseCoord(x,y);     //Where are we now
  BMSource := Table1.GetBookmark;           //Remember Source
  SourcePos := Table1.FieldByName('Pos').AsInteger;  //Remember SourcePosValue
  Table1.MoveBy(GridCoord.y-RowIndex);      //got to DestRecord
  DestPos := Table1.FieldByName('Pos').AsInteger;  //Remember DestPosValue
  Table1.Edit;                              //Avoiding keyviolation
  Table1.FieldByName('Pos').AsInteger := -1;//Park DestRecord
  Table1.Post;
  BMDest := Table1.GetBookmark;             //Remember DestRecord
  Table1.GotoBookmark(BMSource);            //Goto to SourceRecord
  Table1.Edit;                              //Update Pos From DestRecord
  Table1.FieldByName('Pos').AsInteger := DestPos;
  Table1.Post;
  Table1.GotoBookmark(BMDest);              //Goto to DestRecord
  Table1.Edit;                              //Update Pos From SourceRecord
  Table1.FieldByName('Pos').AsInteger := SourcePos;
  Table1.Post;
  Table1.FreeBookmark(BMSource);            //Forget the Rembering
  Table1.FreeBookmark(BMDest);
  Table1.EnableControls;                    //Show The Change
  InDrag := False;                          //Dragging done
end;


end.


meikl ;-)
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LVL 9

Expert Comment

by:ginsonic
ID: 6471509
listening
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Author Comment

by:Mangolab
ID: 6472486
That's great thanks very much for your help.
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