在问一次控件开发的有关属性的问题，真是郁闷！ ( 积分: 10 )

前几天我过一次，根据各位大侠的指点，还是不行啊。不知道是不是俺写的不对。
俺现在写了一个最简单的例子：
unit Edit1;

interface

uses
SysUtils, Classes, Controls, StdCtrls,graphics,dialogs;

type

TMaskInputWay = ( tlInput,tlOutput,tlFix,tlHide,tlInOut);

TScreenInfo = class(TGraphicsObject)
private
FInputWay:TMaskInputWay;
procedure SetInputWay(value:TMaskInputWay);
public
constructor create(Owner:Tcomponent);
destructor Destroy; override;
published
property inputway:TMaskInputWay read Finputway write setinputway;
end;

TEdit1 = class(TEdit)
private

FScreenInfo:TScreenInfo;
procedure setcomponent(sender:Tobject);
procedure SetScreenInfo(value:TscreenInfo);
{ Private declarations }
protected
{ Protected declarations }
public
constructor create(Owner:Tcomponent);override;
destructor destroy;override;
{ Public declarations }
published
property screeninfo:TScreenInfo read FScreenInfo Write SetScreenInfo;
{ Published declarations }
end;

procedure Register;

implementation

procedure Register;
begin
RegisterComponents('Standard', [TEdit1]);
end;

{ TSreenInfo }

constructor TScreenInfo.create(Owner: Tcomponent);
begin
FInputWay:=tlInput;
end;

destructor TScreenInfo.Destroy;
begin
inherited;
end;

procedure TScreenInfo.SetInputWay(value: TMaskInputWay);
begin
Finputway:=value;
end;

{ TEdit1 }

constructor TEdit1.create(Owner: Tcomponent);
begin
inherited;
FScreenInfo:=TScreenInfo.create(self);
FScreenInfo.onchange:=setcomponent;
end;

destructor TEdit1.destroy;
begin
FScreenInfo.Free;
inherited;
end;

procedure TEdit1.setcomponent(sender:Tobject);
begin


showmessage('hello');

end;

procedure TEdit1.SetScreenInfo(value:TscreenInfo);
begin
FscreenInfo.Assign(value);

end;

end.
该控件的思路是：从Tedit类继承，增加了一个screeninfo类属性。screeninfo是一个Tscreeninfo的实例，下面有一个inputway属性。
然后安装控件。
新建一个项目，放置一个Tedit1的控件testedit，在object inspertor里面修改inputway的值，根据程序的思路，应当执行setcomponent过程，就是执行 showmessage('hello')这一句。
可是俺更改inputway的值的时候，并没有出现hello这么一个信息窗口啊。
不知道为什么？？按理说我在程序里面已经设置了Fscreeninfo的onchange事件等于setcomponent了，应当出现hello这一信息窗才对啊。

前几天我过一次，根据各位大侠的指点，还是不行啊。不知道是不是俺写的不对。
俺现在写了一个最简单的例子：
unit Edit1;

interface

uses
SysUtils, Classes, Controls, StdCtrls,graphics,dialogs;

type

TMaskInputWay = ( tlInput,tlOutput,tlFix,tlHide,tlInOut);

TScreenInfo = class(TGraphicsObject)
private
FInputWay:TMaskInputWay;
procedure SetInputWay(value:TMaskInputWay);
public
constructor create(Owner:Tcomponent);
destructor Destroy; override;
published
property inputway:TMaskInputWay read Finputway write setinputway;
end;

TEdit1 = class(TEdit)
private

FScreenInfo:TScreenInfo;
procedure setcomponent(sender:Tobject);
procedure SetScreenInfo(value:TscreenInfo);
{ Private declarations }
protected
{ Protected declarations }
public
constructor create(Owner:Tcomponent);override;
destructor destroy;override;
{ Public declarations }
published
property screeninfo:TScreenInfo read FScreenInfo Write SetScreenInfo;
{ Published declarations }
end;

procedure Register;

implementation

procedure Register;
begin
RegisterComponents('Standard', [TEdit1]);
end;

{ TSreenInfo }

constructor TScreenInfo.create(Owner: Tcomponent);
begin
FInputWay:=tlInput;
end;

destructor TScreenInfo.Destroy;
begin
inherited;
end;

procedure TScreenInfo.SetInputWay(value: TMaskInputWay);
begin
Finputway:=value;
end;

{ TEdit1 }

constructor TEdit1.create(Owner: Tcomponent);
begin
inherited;
FScreenInfo:=TScreenInfo.create(self);
FScreenInfo.onchange:=setcomponent;
end;

destructor TEdit1.destroy;
begin
FScreenInfo.Free;
inherited;
end;

procedure TEdit1.setcomponent(sender:Tobject);
begin


showmessage('hello');

end;

procedure TEdit1.SetScreenInfo(value:TscreenInfo);
begin
FscreenInfo.Assign(value);

end;

end.
该控件的思路是：从Tedit类继承，增加了一个screeninfo类属性。screeninfo是一个Tscreeninfo的实例，下面有一个inputway属性。
然后安装控件。
新建一个项目，放置一个Tedit1的控件testedit，在object inspertor里面修改inputway的值，根据程序的思路，应当执行setcomponent过程，就是执行 showmessage('hello')这一句。
可是俺更改inputway的值的时候，并没有出现hello这么一个信息窗口啊。
不知道为什么？？按理说我在程序里面已经设置了Fscreeninfo的onchange事件等于setcomponent了，应当出现hello这一信息窗才对啊。

修改TScreenInfo.SetInputWay的写事件！

procedure TScreenInfo.SetInputWay(value: TMaskInputWay);
begin
if Finputway:=value then Exit;
Finputway:=value;
if Assigned(ONchange) then
ONchange(Self);
end;