Controls 属性与继承 TShape 类的小练习

本例效果图:

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代码文件:

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unit Unit1;



interface



uses

  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

  Dialogs, StdCtrls, ExtCtrls;



type

  TMyShape = class(TShape)

  protected

    procedure CMMouseenter(var Message: TMessage); message CM_MOUSEENTER;

    procedure CMMouseleave(var Message: TMessage); message CM_MOUSELEAVE;

  end;



  TForm1 = class(TForm)

    Panel1: TPanel;

    Button1: TButton;

    Button2: TButton;

    procedure Button1Click(Sender: TObject);

    procedure Button2Click(Sender: TObject);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



procedure TForm1.Button1Click(Sender: TObject);

const

  W = 50;

  H = 50;

var

  shape: TMyShape;

begin

  shape := TMyShape.Create(Self);

  shape.Parent := Panel1;

  shape.Width := W;

  shape.Height := H;

  Randomize;

  shape.Left := Random(Panel1.ClientWidth - W);

  shape.Top := Random(Panel1.ClientHeight - H);

  shape.Brush.Color := Random($FFFFFF);

end;



procedure TForm1.Button2Click(Sender: TObject);

var

  i: Integer;

begin

  if Panel1.ControlCount = 0 then Exit;

  Randomize;

  i := Random(Panel1.ControlCount - 1);

  Panel1.Controls[i].Free;

end;





{ TMyShape }



procedure TMyShape.CMMouseenter(var Message: TMessage);

const

  s = '当前 %s 的颜色值是: %.6x';

var

  WCtrl: TWinControl;

begin

  WCtrl := Parent;

  while WCtrl.HasParent do WCtrl := WCtrl.Parent;

  if WCtrl is TForm then TForm(WCtrl).Caption := Format(s, [ClassName,Brush.Color]);

  inherited;

end;



procedure TMyShape.CMMouseleave(var Message: TMessage);

const

  s = 'Form1';

var

  WCtrl: TWinControl;

begin

  WCtrl := Parent;

  while WCtrl.HasParent do WCtrl := WCtrl.Parent;

  if WCtrl is TForm then TForm(WCtrl).Caption := s;

  inherited;

end;



end.


 
   

窗体文件:

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object Form1: TForm1

  Left = 0

  Top = 0

  Caption = 'Form1'

  ClientHeight = 212

  ClientWidth = 395

  Color = clBtnFace

  Font.Charset = DEFAULT_CHARSET

  Font.Color = clWindowText

  Font.Height = -11

  Font.Name = 'Tahoma'

  Font.Style = []

  OldCreateOrder = False

  PixelsPerInch = 96

  TextHeight = 13

  object Panel1: TPanel

    Left = 8

    Top = 8

    Width = 297

    Height = 193

    Caption = 'Panel1'

    TabOrder = 0

  end

  object Button1: TButton

    Left = 311

    Top = 40

    Width = 75

    Height = 25

    Caption = #28155#21152

    TabOrder = 1

    OnClick = Button1Click

  end

  object Button2: TButton

    Left = 311

    Top = 85

    Width = 75

    Height = 25

    Caption = #38543#26426#21024#38500

    TabOrder = 2

    OnClick = Button2Click

  end

end