dbgrid.htm

对于学习很有帮助

      or (flds = '') then begin
        CancelRange;
      end else begin
        SetRangeStart;
        for i := 1 to n do begin
          val := Cells[1,i];
          if val <> '' then begin
            FieldByName(Cells[0,i]).AsString := val;
          end;
        end;

        SetRangeEnd;  { Set range end to match range start }
        for i := 1 to n do begin
          val := Cells[1,i];
          if val <> '' then begin
            FieldByName(Cells[0,i]).AsString := val;
          end;
        end;
        ApplyRange;
      end;

      Refresh;
    end;  { with CallingGrid.DataSource.DataSet }
  end;  { with dlgQBF.gridQBF }

  dlgQBF.Hide;
end;

end.
</PRE><HR>

<H1><A NAME="dbgrid6">DBGRID saving the user configuration</A></H1>
<I>[Cosimo Laddomada, [e-mail]]</i><p>


<PRE>Is their a way to save the column order of a grid after the user
reorders the columns via drag n drop.</PRE>

I resolved this problem time ago for my one application. Following code is
adapted for you, not tested, but I think it works fine. It create, save and
load configuration's file for order AND SIZE too of fields. I'm at your
disposal for further into something. <p>

<HR><pre>
procedure TMainForm.NewIni(const NomeIni: string);
var F: System.Text;
    i: Byte;
begin
  System.Assign(F, NomeIni);
  System.ReWrite(F);
  System.WriteLn(F, '[Campi_Ordine]');
  for i:=1 to Table1.FieldCount do
    System.WriteLn(F, 'Campo',i,'=',Table1.Fields[i-1].FieldName);
  System.WriteLn(F, '');
  System.WriteLn(F, '[Campi_Size]');
  for i:=1 to Table1.FieldCount do
    System.WriteLn(F, 'Campo',i,'=',Table1.Fields[i-1].DisplayWidth);
  System.Close(F);
end;

procedure TMainForm.SaveIni(const FN: String);
var Ini: TIniFile;
    i: Integer;
begin
  NewIni(FN);
  Ini := TIniFile.Create(FN);
  with Ini do
  begin
    for i:=1 to Table1.FieldCount do
    begin
      S:= Table1.Fields[i-1].FieldName;
      WriteString('Campi_Ordine', 'Campo'+IntToStr(i), 
        Table1.Fields[i-1].FieldName);
      WriteInteger('Campi_Size', 'Campo'+IntToStr(i),
        Table1.Fields[i-1].DisplayWidth);
    end;
  end;
  Ini.Free;
end;

procedure TMainForm.LoadIni(const FN: String);
var Ini: TIniFile;
    i: Integer;
    j: Longint;
    S: String;

    function MyReadInteger(const Section, Ident: string): Longint;
    begin
      result := Ini.ReadInteger(Section, Ident, -1);
      if result=-1 then
        raise Exception.Create('Errore nel file di configurazione.');
    end;

    function MyReadString(const Section, Ident: string): String;
    begin
      result := Ini.ReadString(Section, Ident, '');
      if result='' then
        raise Exception.Create('Errore nel file di configurazione.');
    end;

begin
  Ini := TIniFile.Create(FN);
  try
    with Ini do
    begin
      for i:=1 to Table1.FieldCount do
      begin
        S:= MyReadString('Campi_Ordine', 'Campo'+IntToStr(i));
        j:= MyReadInteger('Campi_Size', 'Campo'+IntToStr(i));
        Table1.FieldByName(S).Index := i-1;
        Table1.FieldByName(S).DisplayWidth := j;
      end;
    end;
  finally
    Ini.Free;
  end;
end;
</PRE><HR>

<p><H1><A NAME="dbgrid7">DBGrid resize<img src="../images/new.gif" width=28 height=11 border=0 alt=" [NEW]"></p></A></H1>

<PRE>I have a form. In that an Edit field, an SQL Query, a DBGrid and a Button.
I can write into the edit, and the Query result will put into the grid.
How can I resize the grid and the form to the fields size which appears in
the grid. The fields Which I select with the query does not fill the full
size of the grid or does not fit into it.</PRE>

You can change the size of a column at run-time by changing the DisplayWidth
property of the underlying field object...<p>

<Hr><PRE>MyTableMyField.DisplayWidth := Length(MyTableMyField.value);</PRE><HR>

If you need to actually calculate the width of the entire grid, use the
following (from a tips library)...<p>

<Hr><PRE>function NewTextWidth(fntFont : TFont; const sString : OpenString) :

  integer;
var
  fntSave : TFont;
begin
  result := 0;
  fntSave := Application.MainForm.Font;
  Application.MainForm.Font := fntFont;
  try
    result := Application.MainForm.Canvas.TextWidth(sString);
  finally
    Application.MainForm.Font := fntSave;
  end;
end;


{ calculate the width of the grid needed to exactly display with no   }
{ horizontal scrollbar and with no extra space between the last       }
{ column and the vertical scrollbar.  The grid's datasource must be   }

{ properly set and the datasource's dataset must be properly set,     }
{ though it need not be open.  Note:  this width includes the width   }
{ of the vertical scrollbar, which changes based on screen            }
{ resolution.  These changes are compensated for.                     }

function iCalcGridWidth
  (
  dbg : TDBGrid { the grid to meaure }
  )
  : integer; { the "exact" width }

const
  cMEASURE_CHAR   = '0';
  iEXTRA_COL_PIX  = 4;
  iINDICATOR_WIDE = 11;

var
  i, iColumns, iColWidth, iTitleWidth, iCharWidth : integer;
begin
  iColumns := 0;
  result := GetSystemMetrics(SM_CXVSCROLL);
  iCharWidth := NewTextWidth(dbg.Font, cMEASURE_CHAR);
  with dbg.dataSource.dataSet do
    for i := 0 to FieldCount - 1 do with Fields[i] do
      if visible then
      begin
        iColWidth := iCharWidth * DisplayWidth;
        if dgTitles in dbg.Options then
        begin
          iTitleWidth := NewTextWidth(dbg.TitleFont, DisplayLabel);

          if iColWidth &lt; iTitleWidth then iColWidth := iTitleWidth;
        end;
        inc(iColumns, 1);
        inc(result, iColWidth + iEXTRA_COL_PIX);
      end;
  if dgIndicator in dbg.Options then
  begin
    inc(iColumns, 1);
    inc(result, iINDICATOR_WIDE);
  end;
  if dgColLines in dbg.Options
    then inc(result, iColumns)
    else inc(result, 1);
end;
</PRE><HR>

I had to use the function NewTextWidth, rather than the Grid's
Canvas.TextWith as the Canvas of the Grid may not initialized when you need
to call iCalcGridWidth.<p>

<P><H1><A NAME="dbgrid8">Dragging from DbGrid<IMG SRC="../images/new.gif" WIDTH=28 HEIGHT=11 BORDER=0 ALT=" [NEW]"></P></A></H1>

<PRE>Has someone achieved dragging things from a DbGrid ?
You can create your own descendant of TDBGrid (or TDBCustomGrid) and
customize it to your needs.</PRE>

<I>[Demian, [e-mail]]</I><P>
Do an Origami with the code at the end of this message, save it as DBGrid.pas,
and install it. You'll have a new component EDBGrid with two new events:
OnMouseDown and OnMouseUp.
I don't consider it a 'proprietary information': it's a Delphi Bug!
Originally, this two events should have been part of the DBGrid component.

<HR><PRE>
unit Dbgrid;

interface

uses
  DBGrids, Controls, Classes;

type
  TEDBGrid = class(TDBGrid)
  private
    FOnMouseDown: TMouseEvent;
    FOnMouseUp: TMouseEvent;
  protected
    procedure MouseDown(Button: TMouseButton; Shift: TShiftState; X, Y:
Integer); override;
    procedure MouseUp(Button: TMouseButton; Shift: TShiftState; X, Y:
Integer); override;
  published
    Property OnMouseDown : TMouseEvent read FOnMouseDown write
FOnMouseDown ;
    Property OnMouseUp : TMouseEvent read FOnMouseUp write FOnMouseUp ;
end;

procedure Register;

implementation

procedure Register;
begin
  RegisterComponents('Data Controls',[TEDBGrid]);
end;

procedure TEDBGrid.MouseDown(Button: TMouseButton; Shift: TShiftState;
X, Y: Integer);
begin
  if Assigned(FOnMouseDown) then
    FOnMouseDown(Self,Button,Shift,X,Y);
  inherited MouseDown(Button,Shift,X,Y);
end;

procedure TEDBGrid.MouseUp(Button: TMouseButton; Shift: TShiftState; X,
Y: Integer);
begin
  if Assigned(FOnMouseUp) then
    FOnMouseUp(Self,Button,Shift,X,Y);
  inherited MouseUp(Button,Shift,X,Y);
end;

end.
</PRE><HR>


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