delphi 给TComboBox 添加图标

首先: 这有现成的控件: TComboBoxEx, 没必要使用 TComboBox; 非要在 TComboBox 基础上添加, 也可以.

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本例效果图:

 

 代码文件:
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unit Unit1;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls, ImgList, ComCtrls;

type
TForm1 = class(TForm)
ComboBox1: TComboBox;
ImageList1: TImageList;
procedure FormCreate(Sender: TObject);
procedure ComboBox1DrawItem(Control: TWinControl; Index: Integer;
Rect: TRect; State: TOwnerDrawState);
procedure FormDestroy(Sender: TObject);
end;

var
Form1: TForm1;

implementation

{$R *.dfm}

var
Bits: array[0..3] of TBitmap;

procedure TForm1.FormCreate(Sender: TObject);
var
i: Integer;
begin
for i := 0 to Length(Bits)-1 do
begin
Bits[i] := TBitmap.Create;
ImageList1.GetBitmap(i, Bits[i]);
ComboBox1.Items.Add(Format('Item %d', [i]));
end;

ComboBox1.Style := csOwnerDrawVariable;
ComboBox1.ItemHeight := Bits[0].Height + 4;
ComboBox1.ItemIndex := 0;
end;

procedure TForm1.ComboBox1DrawItem(Control: TWinControl; Index: Integer;
Rect: TRect; State: TOwnerDrawState);
begin
ComboBox1.Canvas.FillRect(Rect);

ComboBox1.Canvas.BrushCopy(Bounds(Rect.Left+2, Rect.Top+2, Bits[Index].Width, Bits[Index].Height),
Bits[Index],
Bounds(0, 0, Bits[Index].Width, Bits[Index].Height),
clBlack);
ComboBox1.Canvas.TextOut(Rect.Left + 24, Rect.Top + 3, ComboBox1.Items[Index]);
end;

procedure TForm1.FormDestroy(Sender: TObject);
var
i: Integer;
begin
for i := 0 to Length(Bits)-1 do
Bits[i].Free;
end;

end.