问大老：关于控件数组的响应事件，以下代码为什么不对！

Question

unit Unit5;interfaceuses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ExtCtrls, CheckLst;type
  TlbForm = class(TForm)
    CheckListBox1: TCheckListBox;
    GroupBox: TGroupBox;
    procedure FormShow(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    //procedure CheckBox50Click(Sender: TObject);
    procedure CheckBoxClick(Sender: TObject);   
  private
    { Private declarations }
     arrcheckbox: array[1..21] of Tcheckbox;
  public
    { Public declarations }
     procedure checkboxarryclick(Sender: Tobject);
  end;var
  lbForm: TlbForm;
  counter: integer;implementation{$R *.dfm}procedure TlbForm.FormShow(Sender: TObject);
begin
for counter:= 1 to 21 do
 begin
 arrcheckbox[counter]:=Tcheckbox.Create(self);
 arrcheckbox[counter].Parent:=groupbox;
 arrcheckbox[counter].Top:=counter*17;
 arrcheckbox[counter].Left:=16;
 end;
 end;procedure TlbForm.FormCreate(Sender: TObject);
begin
arrcheckbox[counter].OnClick:= checkboxarryclick;
end;
procedure Tlbform.checkboxarryclick(sender: Tobject);
   begin
   showmessage('ok');
   end;procedure TlbForm.CheckBoxClick(Sender: TObject);
begin
showmessage('fdsdfs');
end;end.

Answer 1

procedure TlbForm.FormShow(Sender: TObject);
begin
  for counter:= 1 to 21 do
  begin
    arrcheckbox[counter]:=Tcheckbox.Create(self);
    arrcheckbox[counter].Parent:=groupbox;
    arrcheckbox[counter].Top:=counter*17;
    arrcheckbox[counter].Left:=16;
    arrcheckbox[counter].OnClick:= checkboxarryclick;
  end;
end;

Answer 2

procedure TlbForm.FormCreate(Sender: TObject);
begin
arrcheckbox[counter].OnClick:= checkboxarryclick;
end;is wrong
formcreate happens before show do
so what is var counter's content?
you can uses rtti and attribute tag to reach your aim;

Answer 3

onCreate事件在onshow事件前触发.
procedure TlbForm.FormCreate(Sender: TObject);
begin//arrcheckbox[counter]还没有被创建
arrcheckbox[counter].OnClick:= checkboxarryclick;
end;

Answer 4

arrcheckbox[counter].OnClick:= checkboxarryclick;
一句应该放在TlbForm.FormShow中的for循环中。

Answer 5

unit Unit1;interfaceuses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure FormShow(Sender: TObject);
  private
    arrcheckbox: array[1..21] of Tcheckbox;
    { Private declarations }
  public
    procedure checkboxarryclick(Sender: Tobject);
    { Public declarations }
  end;var
  Form1: TForm1;
  counter: Integer;
implementation{$R *.dfm}procedure TForm1.checkboxarryclick(Sender: Tobject);
begin
  if Sender = arrcheckbox[1] then//处理第一个复选框的代码
  begin
    ShowMessage('我是复选框1');
  end;
  if sender = arrcheckbox[2] then
  begin
    Close;
  end;
end;procedure TForm1.FormShow(Sender: TObject);
begin
for counter:= 1 to 21 do
 begin
 arrcheckbox[counter]:=Tcheckbox.Create(self);
 arrcheckbox[counter].Parent:=self;
 arrcheckbox[counter].Top:=counter*17;
 arrcheckbox[counter].Left:=16;
 arrcheckbox[counter].Caption := '复选框' + IntToStr(counter);
 arrcheckbox[counter].OnClick := checkboxarryclick;
 end;
end;end.