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Delphi学习:在Listbox加背景图
文章来源:csdn 作者:chenzhechenge

 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

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