在Listboxes中加背景图

2019-11-17 05:06:33

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Delphi

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lbOwnerDrawVariabble。

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.

下面给出完整的主程序源程序：

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;

Th tmap3.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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