【请教】VCL组件问题

Question

我要继承TEdit类写一个简单的组件，当获得输入焦点时变红色，失去输入焦点时变白色，请问怎么写比较简单,谢谢

Answer 1

没有必要写成组件,用OnEnter和OnExit就能实现.

Answer 2

procedure TForm1.Edit1Enter(Sender: TObject);
begin
  edit1.Color := clRed;
end;procedure TForm1.Edit1Exit(Sender: TObject);
begin
  edit1.Color := clWhite;
end;

Answer 3

unit Unit1;interfaceuses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls;type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);  private
    { Private declarations }
  public
    { Public declarations }
  end;  TExEdit = class(TEdit)
  private
  public
    procedure WndProc(var message: TMessage); override;
  end;
var
  Form1: TForm1;implementation{$R *.DFM}{ TExEdit }procedure TExEdit.WndProc(var message: TMessage);
begin
  case Message.Msg of
    WM_SETFOCUS:
      Self.Color:=clred;
    WM_KILLFOCUS:
      Self.Color:=clWhite;
  end;
  inherited WndProc(message);end;procedure TForm1.Button1Click(Sender: TObject);
var e:TExEdit;
begin
  e:=TExEdit.Create(self);
  e.Parent:=self;
end;end.在窗体上加个Button1再把代码拷贝进去就ok拉

Answer 4

unit EditEx;interfaceuses
  SysUtils, Classes, Controls, StdCtrls, Graphics;type
  TEditEx = class(TEdit)
  private
    { Private declarations }
    procedure Enter(Sender: TObject);
    procedure Exit(Sender: TObject);
  protected
    { Protected declarations }
  public
    { Public declarations }
    constructor Create(AOwner: TComponent); override;
  published
    { Published declarations }
  end;procedure Register;implementationprocedure Register;
begin
  RegisterComponents('loveking', [TEditEx]);
end;procedure TEditEx.Enter(Sender: TObject);
begin
    self.Color:=clBlue;
end;procedure TEditEx.Exit(Sender: TObject);
begin
    self.Color:=clWhite;
end;constructor TEditEx.Create(AOwner: TComponent);
begin
    self.OnEnter:=Enter;
    self.OnExit:=Exit;
end;end.
//----------------组件形式的-----------------------------------