如何正确定位 DBGrid 中居中的图标？答案

【问题标题】：How Can I correctly position the icons centered in a DBGrid?如何正确定位 DBGrid 中居中的图标？
【发布时间】：2014-05-25 15:35:41
【问题描述】：

列宽是：48 图标宽度为：32。

这就是我想画的方式：

12345678901234567890123456789012345678901234567   => 48, Column witdh
--------1234567890123456789012345678901--------   => 32, Icon width     
12345678-------------------------------12345678   => blank spaces 8 (before and after)

这是一个 SSCCE：

.PAS：

unit uMain;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, DB, ADODB, Provider, ImgList, Grids, DBGrids, DBClient, StdCtrls,
  ExtCtrls;

type
  TForm1 = class(TForm)
    ClientDataSet1: TClientDataSet;
    DBGrid1: TDBGrid;
    DataSource1: TDataSource;
    ImageList1: TImageList;
    Button1: TButton;
    ClientDataSet1FieldA: TIntegerField;
    ClientDataSet1FieldB: TStringField;
    ClientDataSet1Status: TIntegerField;
    procedure DBGrid1DrawColumnCell(Sender: TObject; const Rect: TRect;
      DataCol: Integer; Column: TColumn; State: TGridDrawState);
    procedure Button1Click(Sender: TObject);
    procedure FormCreate(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.DBGrid1DrawColumnCell(Sender: TObject; const Rect: TRect;
  DataCol: Integer; Column: TColumn; State: TGridDrawState);
var
  FIcon: TIcon;
  X,Y: Integer;
begin
  if Assigned(Column.Field) and (Column.FieldName = 'Status') then
  begin
    if Column.Field.DataSet.RecordCount = 0 then
      Exit;

    if Column.Field.Tag <> 0 then
      FIcon := TIcon(Pointer(Column.Field.Tag))
    else
    begin
      FIcon := TIcon.Create;
      try
        ImageList1.GetIcon(0, FIcon);
        Column.Field.Tag := Integer(Pointer(FIcon));
      except
        FIcon.Free;
        raise;
      end;
    end;

    if Assigned(FIcon) then
    begin
      if Column.Width < FIcon.Width then
      begin
        Column.Width := FIcon.Width;
        X:= Rect.Left;
        Y:= Rect.Top;
      end
      else
      begin
        //X:= Rect.Left + (Column.Width - FIcon.Width) div 2;
        //or 
        X:= Rect.Left + Round((Column.Width - FIcon.Width) / 2);
        Y:= Rect.Top;
      end;

      DBGrid1.Canvas.Draw(X, Y, FIcon);
    end;
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  ClientDataSet1.DisableControls;
  try
    ClientDataSet1.Append;
    ClientDataSet1FieldA.AsInteger := 1;
    ClientDataSet1FieldB.AsString := 'One';
    ClientDataSet1.Post;

    ClientDataSet1.Append;
    ClientDataSet1FieldA.AsInteger := 2;
    ClientDataSet1FieldB.AsString := 'Two';
    ClientDataSet1.Post;

    ClientDataSet1.Append;
    ClientDataSet1FieldA.AsInteger := 3;
    ClientDataSet1FieldB.AsString := 'Three';
    ClientDataSet1.Post;
  finally
    ClientDataSet1.EnableControls;
  end;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  ClientDataSet1.CreateDataSet;
end;

end.

.DFM：

object Form1: TForm1
  Left = 491
  Top = 151
  Width = 681
  Height = 471
  Caption = 'Form1'
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'MS Sans Serif'
  Font.Style = []
  OldCreateOrder = False
  OnCreate = FormCreate
  PixelsPerInch = 96
  TextHeight = 13
  object DBGrid1: TDBGrid
    Left = 8
    Top = 8
    Width = 561
    Height = 417
    DataSource = DataSource1
    Options = [dgTitles, dgIndicator, dgColumnResize, dgColLines, dgRowLines, dgTabs, dgConfirmDelete, dgCancelOnExit]
    TabOrder = 0
    TitleFont.Charset = DEFAULT_CHARSET
    TitleFont.Color = clWindowText
    TitleFont.Height = -11
    TitleFont.Name = 'MS Sans Serif'
    TitleFont.Style = []
    OnDrawColumnCell = DBGrid1DrawColumnCell
    Columns = <
      item
        Expanded = False
        FieldName = 'FieldA'
        Visible = True
      end
      item
        Expanded = False
        FieldName = 'FieldB'
        Visible = True
      end
      item
        Alignment = taCenter
        Expanded = False
        FieldName = 'Status'
        Font.Charset = DEFAULT_CHARSET
        Font.Color = clWindow
        Font.Height = -11
        Font.Name = 'MS Sans Serif'
        Font.Style = []
        ReadOnly = True
        Width = 47
        Visible = True
      end>
  end
  object Button1: TButton
    Left = 576
    Top = 8
    Width = 75
    Height = 25
    Caption = 'Show'
    TabOrder = 1
    OnClick = Button1Click
  end
  object ClientDataSet1: TClientDataSet
    Aggregates = <>
    FieldDefs = <>
    IndexDefs = <>
    Params = <>
    StoreDefs = True
    Left = 504
    Top = 24
    object ClientDataSet1FieldA: TIntegerField
      FieldName = 'FieldA'
    end
    object ClientDataSet1FieldB: TStringField
      FieldName = 'FieldB'
    end
    object ClientDataSet1Status: TIntegerField
      FieldName = 'Status'
    end
  end
  object DataSource1: TDataSource
    DataSet = ClientDataSet1
    Left = 504
    Top = 72
  end
  object ImageList1: TImageList
    BlendColor = clWhite
    BkColor = clWhite
    DrawingStyle = dsTransparent
    Left = 504
    Top = 120
    Bitmap = {
      494C010101000400040010001000FFFFFF00FF10FFFFFFFFFFFFFFFF424D3600
      0000000000003600000028000000400000001000000001002000000000000010
      000000000000000000000000000000000000FFFFFF00FFFFFF00FFFFFF00FCFC
      FC00F1F5F300D7EAE400D1E8E000D0E8E000D0E7E000D0E8E000D8EBE500F4F6
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  end
end

【问题讨论】：

标签： windows delphi draw vcl delphi-6

【解决方案1】：

由于 VCL 中的错误，在为图标分配新图像时，不会更新图标的内部大小 (FSize) 值。这个错误（1，2，...）已经得到解决，而且您的测试用例确实可以正常工作，f.i.，D2007。

由于该错误，报告的图标大小是默认系统图标大小 (GetSystemMetrics(SM_CXICON))。因此，在您的情况下，它是“32”（默认情况下）而不是“16”。在计算绘制图像的位置时将其考虑在内，或者在链接报告之一或其他报告中使用其中一种解决方法，或者设计自己的解决方法。在这种特殊情况下，您可以简单地使用图像列表的尺寸：

X:= Rect.Left + Round((Column.Width - ImageList1.Width) / 2);

【讨论】：

+1。非常感谢，Sertac。我没有意识到图标大小返回 32。
其实我没有意识到图标大小是 16

【解决方案2】：

使用 TIcon 的 TBitmap

procedure TForm1.DBGrid1DrawColumnCell(Sender: TObject; const Rect: TRect;
  DataCol: Integer; Column: TColumn; State: TGridDrawState);
var
  FIcon: TBitmap;
  X,Y: Integer;
begin
  if Assigned(Column.Field) and (Column.FieldName = 'Status') then
  begin
    if Column.Field.DataSet.RecordCount = 0 then
      Exit;

    if Column.Field.Tag <> 0 then
      FIcon := TBitmap(Pointer(Column.Field.Tag))
    else
    begin
      FIcon := TBitmap.Create;
      try
        ImageList1.GetBitmap(0, FIcon);
        Column.Field.Tag := Integer(Pointer(FIcon));
      except
        FIcon.Free;
        raise;
      end;
    end;

    if Assigned(FIcon) then
    begin
      if Column.Width < FIcon.Width then
      begin
        Column.Width := FIcon.Width;
        X:= Rect.Left;
        Y:= Rect.Top;
      end
      else
      begin
        //X:= Rect.Left + (Column.Width - FIcon.Width) div 2;
        //or
        X:= Rect.Left + Round((Column.Width - FIcon.Width) / 2);
        Y:= Rect.Top;
      end;

      DBGrid1.Canvas.Draw(X, Y, FIcon);
    end;
  end;
end;

【讨论】：

谢谢，这会给我带来麻烦吗？图片扩展名为 .ico。作为位图检索可以吗？
如果在TImageList中，没问题。