在Listbox加背景图

核心提示：1. 建立一个窗体2. 放一个ComboBox和Listbox3. 改变Component的Style为csOwnerDrawVariable和ListBox的Style为lbOwnerDrawVariable。4. 声明5个TBitmap的全局变量5. 覆盖Form的OnCreate.6. 覆盖Combo

1.  建立一个窗体
2.  放一个ComboBox和Listbox
3.  改变Component的Style为csOwnerDrawVariable和ListBox的Style为lbOwnerDrawVariable。
4.  声明5个TBitmap的全局变量
5.  覆盖Form的OnCreate.
6.  覆盖ComboBox的OnDraw.
7.  覆盖ComboBox的OnMeasureItem.
8.  释放资源在Form的OnClose.

unit Ownerdrw;

interface

uses
  SysUtils, WinTypes, WinPRocs, Messages, Classes, Graphics, Controls,
  Forms, Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
　  ComboBox1: TComboBox;
　  ListBox1: TListBox;
　  procedure FormCreate(Sender: TObject);
　  procedure FormClose(Sender: TObject; var Action: TCloseAction);
　  procedure ComboBox1DrawItem(Control: TWinControl; Index: Integer;
　　  Rect: TRect; State: TOwnerDrawState);
　  procedure ComboBox1MeasureItem(Control: TWinControl; Index: Integer;
　　  var Height: Integer);
　  procedure ListBox1DrawItem(Control: TWinControl; Index: Integer;
　　  Rect: TRect; State: TOwnerDrawState);
　  procedure ListBox1MeasureItem(Control: TWinControl; Index: Integer;
　　  var Height: Integer);

  private
　  { Private declarations }

  public
　  { Public declarations }

  end;

var
  Form1: TForm1;
  TheBitmap1, TheBitmap2, TheBitmap3, TheBitmap4,
  TheBitmap5 : TBitmap;
implementation

{$R *.DFM}

procedure TForm1.FormCreate(Sender: TObject);
begin
  TheBitmap1 := TBitmap.Create;
  TheBitmap1.LoadFromFile('C:\delphi\images\buttons\globe.bmp');
  TheBitmap2 := TBitmap.Create;
  TheBitmap2.LoadFromFile('C:\delphi\images\buttons\video.bmp');
  TheBitmap3 := TBitmap.Create;
  TheBitmap3.LoadFromFile('C:\delphi\images\buttons\gears.bmp');
  TheBitmap4 := TBitmap.Create;
  TheBitmap4.LoadFromFile('C:\delphi\images\buttons\key.bmp');
  TheBitmap5 := TBitmap.Create;
  TheBitmap5.LoadFromFile('C:\delphi\images\buttons\tools.bmp');
  ComboBox1.Items.AddObject('Bitmap1: Globe', TheBitmap1);
  ComboBox1.Items.AddObject('Bitmap2: Video', TheBitmap2);
  ComboBox1.Items.AddObject('Bitmap3: Gears', TheBitmap3);
  ComboBox1.Items.AddObject('Bitmap4: Key', TheBitmap4);
  ComboBox1.Items.AddObject('Bitmap5: Tools', TheBitmap5);
  ListBox1.Items.AddObject('Bitmap1: Globe', TheBitmap1);
  ListBox1.Items.AddObject('Bitmap2: Video', TheBitmap2);
  ListBox1.Items.AddObject('Bitmap3: Gears', TheBitmap3);
  ListBox1.Items.AddObject('Bitmap4: Key', TheBitmap4);
  ListBox1.Items.AddObject('Bitmap5: Tools', TheBitmap5);

end;

procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
  TheBitmap1.Free;
  TheBitmap2.Free;
  TheBitmap3.Free;
  TheBitmap4.Free;
  TheBitmap5.Free;
end;

procedure TForm1.ComboBox1DrawItem(Control: TWinControl; Index: Integer;
  Rect: TRect; State: TOwnerDrawState);
var
  Bitmap: TBitmap;
  Offset: Integer;
begin
  with (Control as TComboBox).Canvas do
  begin
　  FillRect(Rect);
　  Bitmap := TBitmap(ComboBox1.Items.Objects[Index]);
　  if Bitmap <> nil then
　  begin
　　  BrushCopy(Bounds(Rect.Left + 2, Rect.Top + 2, Bitmap.Width,
　　　　　　　  Bitmap.Height), Bitmap, Bounds(0, 0, Bitmap.Width,
　　　　　　　  Bitmap.Height), clRed);
　　  Offset := Bitmap.width + 8;
　  end;
　  { display the text }
　  TextOut(Rect.Left + Offset, Rect.Top, Combobox1.Items[Index])
  end;
end;

procedure TForm1.ComboBox1MeasureItem(Control: TWinControl; Index:
　　　　　　　　　　　　　　　　　　  Integer; var Height: Integer);
begin
  height:= 20;
end;

procedure TForm1.ListBox1DrawItem(Control: TWinControl; Index: Integer;
  Rect: TRect; State: TOwnerDrawState);
var
  Bitmap: TBitmap;
  Offset: Integer;
begin
  with (Control as TListBox).Canvas do
  begin
　  FillRect(Rect);
　  Bitmap := TBitmap(ListBox1.Items.Objects[Index]);
　  if Bitmap <> nil then
　  begin
　　  BrushCopy(Bounds(Rect.Left + 2, Rect.Top + 2, Bitmap.Width,
　　　　　　　  Bitmap.Height), Bitmap, Bounds(0, 0, Bitmap.Width,
　　　　　　　  Bitmap.Height), clRed);
　　  Offset := Bitmap.width + 8;
　  end;
　  { display the text }
　  TextOut(Rect.Left + Offset, Rect.Top, Listbox1.Items[Index])
  end;
end;

procedure TForm1.ListBox1MeasureItem(Control: TWinControl; Index: Integer;
  var Height: Integer);
begin
  height:= 20;
end;

end.

//该窗体的DFM文件

object Form1: TForm1
  Left = 211
  Top = 155
  Width = 435
  Height = 300
  Caption = 'Form1'
  Font.Color = clWindowText
  Font.Height = -13
  Font.Name = 'System'
  Font.Style = []
  PixelsPerInch = 96
  OnClose = FormClose
  OnCreate = FormCreate
  TextHeight = 16
  object ComboBox1: TComboBox
　  Left = 26
　  Top = 30
　  Width = 165
　  Height = 22
　  Style = csOwnerDrawVariable
　  ItemHeight = 16
　  TabOrder = 0
　  OnDrawItem = ComboBox1DrawItem
　  OnMeasureItem = ComboBox1MeasureItem
  end
  object ListBox1: TListBox
　  Left = 216
　  Top = 28
　  Width = 151
　  Height = 167
　  ItemHeight = 16
　  Style = lbOwnerDrawVariable
　  TabOrder = 1
　  OnDrawItem = ListBox1DrawItem
　  OnMeasureItem = ListBox1MeasureItem
  end
end