Delphi 10 TDrawGrid - 如何让行正确刷新？

Question

使用 Delphi 10.2 Tokyo。

我使用 DrawCell 方法使一行中的所有列与所选单元格的颜色相同。这允许我让用户点击不同的单元格，但仍显示“选定”行。

这使用 OnSelectCell 方法使原始行和新选择的行无效。多年来一直使用这种方法。

如果我有一个带有水平滚动条的网格，当向右滚动并且用户在单元格中单击时，网格无法正确绘制。

这是一个简单的例子，使用一个 TDrawGrid 和一个 OnDrawCell 事件和一个 OnSelectCell 事件:

表单(DFM)代码:

object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 299
  ClientWidth = 635
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  OldCreateOrder = False
  PixelsPerInch = 96
  TextHeight = 13
  object DrawGrid1: TDrawGrid
    Left = 0
    Top = 0
    Width = 635
    Height = 299
    Align = alClient
    Color = clWhite
    ColCount = 15
    DefaultColWidth = 65
    DefaultRowHeight = 48
    DefaultDrawing = False
    DrawingStyle = gdsGradient
    RowCount = 12
    GradientEndColor = clBtnFace
    GradientStartColor = clBtnFace
    Options = [goThumbTracking]
    ParentShowHint = False
    ShowHint = True
    TabOrder = 0
    OnDrawCell = DrawGrid1DrawCell
    OnSelectCell = DrawGrid1SelectCell
    ColWidths = (
      65
      65
      65
      65
      65
      65
      65
      65
      65
      65
      65
      65
      65
      65
      65)
    RowHeights = (
      48
      48
      48
      48
      48
      48
      48
      48
      48
      48
      48
      48)
  end
end

单位(PAS)代码:

unit Unit1;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants,     System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.Grids, Math;

type
  TGridCracker = class(TDrawGrid)// required to access protected method Invalidaterow - info gleaned from Team B member Peter Below on the Internet
  private
  public
  end;

  TForm1 = class(TForm)
    DrawGrid1: TDrawGrid;
    procedure DrawGrid1DrawCell(Sender: TObject; ACol, ARow: Integer; Rect: TRect; State: TGridDrawState);
    procedure DrawGrid1SelectCell(Sender: TObject; ACol, ARow: Integer; var CanSelect: Boolean);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.DrawGrid1DrawCell(Sender: TObject; ACol, ARow: Integer; Rect: TRect; State: TGridDrawState);
var MyCanvas : TCanvas;
  str : string;
  MyRect : TRect;
begin
  MyCanvas := TDrawGrid(Sender).Canvas;

  MyCanvas.Font.Name := 'Arial'; // drawgrid uses Tahoma 8pt as its default font, not Arial
  MyCanvas.Font.Size := 9;
  MyCanvas.Brush.Color := TDrawGrid(Sender).FixedColor;
  MyCanvas.Font.Color := TDrawGrid(Sender).Font.Color;
  MyCanvas.FillRect(Rect);

  if (ARow = 0) then begin
    str := EmptyStr;
    if (ACol > 0) then begin
        str := ACol.ToString;
    end
    else begin
      str := 'TEST';
    end;

    MyCanvas.Font.Color := clblack; // clGray;
    MyRect.Left := Rect.Left + 1;
    MyRect.Top := Rect.Top + 3;
    MyRect.Right := Rect.Right - 1;
    MyRect.Bottom := Rect.Bottom - 3;
    MyCanvas.FillRect(MyRect);
    MyCanvas.Brush.Color := clGray;
    MyCanvas.FrameRect(MyRect);
    MyCanvas.Brush.Color := clWhite;
    MyCanvas.Font.Style := MyCanvas.Font.Style + [fsBold];

    MyRect.Top := MyRect.Top + 2;
    DrawText(MyCanvas.Handle, pChar(str), -1, MyRect, DT_VCENTER or DT_CENTER);

    MyCanvas.Font.Style := MyCanvas.Font.Style - [fsBold];
  end
  else begin
    if (ACol = 0) then begin
      MyCanvas.Brush.Color := clMaroon;
      MyCanvas.FillRect(Rect);
    end
    else begin//ACol > 0
      if ARow = DrawGrid1.Row then begin
        MyCanvas.Brush.Color := clBlue;
      end
      else begin
        MyCanvas.Brush.Color := clwhite;
      end;

      MyCanvas.FillRect(Rect);

      // other cell drawing of text happens after here
    end;
  end;
end;

procedure TForm1.DrawGrid1SelectCell(Sender: TObject; ACol, ARow: Integer; var CanSelect: Boolean);
begin
  TGridCracker(Sender).InvalidateRow(TGridCracker(Sender).Row);
  TGridCracker(Sender).InvalidateRow(ARow);
end;

end.

运行程序。

单击水平滚动条使第 14 列可见。

单击第 2 行中的第 13 列。

点击第 3 行的第 12 列。

注意到真正困惑的选择模式了吗？

这是结果的屏幕截图:

理想情况下应该有一排蓝色单元格，而不是一团乱麻。第 3 行应为纯蓝色。

在 OnSelectCell 方法中调用 DrawGrid1.Refresh 甚至无法修复它。

关于如何让它真正起作用的任何想法？我不能为此网格使用 RowSelect。

干杯!

张杰

Answer 1

除了不必要的闪烁之外，您的代码似乎没有任何错误。这可以通过使用 OnDrawCell 事件的 State 来解决。

procedure TForm1.DrawGrid1DrawCell(Sender: TObject; ....
var MyCanvas : TCanvas;
  str : string;
  MyRect : TRect;
begin
  MyCanvas := TDrawGrid(Sender).Canvas;

  if gdFixed in State then begin
    MyCanvas.Font.Name := 'Arial'; // drawgrid uses Tahoma 8pt as its default font, not Arial
    MyCanvas.Font.Size := 9;
    MyCanvas.Brush.Color := TDrawGrid(Sender).FixedColor;
    MyCanvas.Font.Color := TDrawGrid(Sender).Font.Color;
    MyCanvas.FillRect(Rect);
  end;

  if (ARow = 0) then begin
    ...

---

错误在 TCustomGrid 的 InvalidateRow 中，它不考虑可能的滚动。列方式相同。

您可以使用 protected BoxRect 方法，该方法使用 GridRectToScreenRect(私有(private))方法将单元格位置转换为屏幕坐标。

procedure TForm1.DrawGrid1SelectCell(Sender: TObject; ACol, ARow: Integer; var CanSelect: Boolean);
var
  Grid: TDrawGrid;
  GR, R: TRect;
begin
  Grid := Sender as TDrawGrid;
  if ARow = Grid.Row then
    Exit;

  GR.Left := Grid.LeftCol;
  GR.Top := Grid.Row;
  GR.Width := Grid.VisibleColCount;
  GR.Height := 0;

  R := TGridCracker(Grid).BoxRect(GR.Left, GR.Top, GR.Right, GR.Bottom);
  InvalidateRect(Grid.Handle, R, False);

  GR.Top := ARow;
  GR.Bottom := ARow;

  R := TGridCracker(Grid).BoxRect(GR.Left, GR.Top, GR.Right, GR.Bottom);
  InvalidateRect(Grid.Handle, R, False);
end;