设置TDBGrid可见行

Question

我想在给定VisibleRows参数的情况下调整TDBGrid高度.网格可能有也可能没有标题.

假设我从数据库中选择了100条记录,但我想调整网格高度以显示前10行(使它们可见).数据集仍将保留100条记录.

即

procedure SetVisibleRows(DBGrid: TCustomDBGrid; VisibleRows: Integer);
begin
  ...
  DBGrid.Height := ???
end;

我知道如何获得可见的行:

type
  TCustomGridHack = class(TCustomGrid);

function GetVisibleRows(DBGrid: TCustomDBGrid): Integer;
begin
   Result := TCustomGridHack(DBGrid).VisibleRowCount;
end;

但是,有没有办法来设置的VisibleRowCount？

Answer 1

这似乎有效（也许可以进一步优化）：

type
  TCustomDBGridHack = class(TCustomDBGrid);

procedure SetVisibleRows(DBGrid: TCustomDBGrid; VisibleRows: Integer);
var
  TitleHeight, RowHeight: Integer;
begin
  with TCustomDBGridHack(DBGrid) do
  begin
    if dgTitles in Options then
    begin
      TitleHeight := RowHeights[0] + GridLineWidth;
      RowHeight := RowHeights[1] + GridLineWidth;
    end
    else
    begin
      TitleHeight := 0;
      RowHeight := RowHeights[0] + GridLineWidth;
    end;
  end;
  DBGrid.ClientHeight := TitleHeight + (RowHeight * VisibleRows) + 1;
end;

TGridDrawInfo或者按照@nil 的建议使用。它产生更准确的结果（我对其进行了一些修改）：

procedure SetVisibleRows(DBGrid: TCustomDBGrid; VisibleRows: Integer);
var
  DrawInfo: TGridDrawInfo;
  TitleHeight, RowHeight: Integer;
begin
  with TCustomDBGridHack(DBGrid) do
  begin
    CalcDrawInfo(DrawInfo);
    TitleHeight := DrawInfo.Vert.FixedBoundary;
    RowHeight := RowHeights[DrawInfo.Vert.FirstGridCell] + DrawInfo.Vert.EffectiveLineWidth;
  end;
  DBGrid.ClientHeight := TitleHeight + (RowHeight * VisibleRows) + 1;
end;

正如@nil 提到的，RowHeight也可以用以下方法计算：

RowHeight := DrawInfo.Vert.GetExtent(DrawInfo.Vert.FirstGridCell) + DrawInfo.Vert.EffectiveLineWidth; 

但我没有注意到任何区别。（应进一步调查）。

上述内容还可以进一步改进，使TDBGrid滚动条调整得更好：

procedure SetVisibleRows(DBGrid: TCustomDBGrid; VisibleRows: Integer);
var
  DrawInfo: TGridDrawInfo;
  TitleHeight, RowHeight: Integer;
  HasActiveDataSet: Boolean;
begin
  if VisibleRows < 0 then VisibleRows := 0;
  HasActiveDataSet := Assigned(DBGrid.DataSource) and
    Assigned(DBGrid.DataSource.DataSet) and
    DBGrid.DataSource.DataSet.Active;
  if HasActiveDataSet then
    DBGrid.DataSource.DataSet.DisableControls;
  try
    with TCustomDBGridHack(DBGrid) do
    begin
      CalcDrawInfo(DrawInfo);
      TitleHeight :=  DrawInfo.Vert.FixedBoundary;
      RowHeight := RowHeights[DrawInfo.Vert.FirstGridCell] + DrawInfo.Vert.EffectiveLineWidth;      
    end;
    DBGrid.ClientHeight := TitleHeight + (RowHeight * VisibleRows) + 1;
  finally
    if HasActiveDataSet then
      DBGrid.DataSource.DataSet.EnableControls;
  end;
end;