Controls 属性与继承 TShape 类的小练习

本例效果图:

---

代码文件:

---

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:

---

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