如何把窗体关闭到系统托盘

unit Unit1;  

interface  

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, ExtCtrls, StdCtrls, AppEvnts;  

type
  TForm1 = class(TForm)
    TrayIcon1: TTrayIcon;
    Button1: TButton;
    procedure TrayIcon1Click(Sender: TObject);
    procedure FormCloseQuery(Sender: TObject; var CanClose: Boolean);
    procedure Button1Click(Sender: TObject);
  end;  

var
  Form1: TForm1;  

implementation  

{$R *.dfm}  

{关闭}
procedure TForm1.Button1Click(Sender: TObject);
begin
  Application.Terminate;
end;  

{点击关闭按钮时让窗体最小化到系统托盘}
procedure TForm1.FormCloseQuery(Sender: TObject; var CanClose: Boolean);
begin
  Tag := Ord(WindowState);
  WindowState := wsMinimized;
  TrayIcon1.SetDefaultIcon;
  TrayIcon1.Visible := True;
  Hide;
  CanClose := False;
end;  

{点击系统托盘中的图标恢复窗口}
procedure TForm1.TrayIcon1Click(Sender: TObject);
begin
  TrayIcon1.Visible := False;
  Show;
  WindowState := TWindowState(tag);
  SetForegroundWindow(Handle);
end;  

end.
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窗体文件:
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object Form1: TForm1
  Left = 0
  Top = 0
  Caption = ‘Form1‘
  ClientHeight = 206
  ClientWidth = 339
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = ‘Tahoma‘
  Font.Style = []
  OldCreateOrder = False
  OnCloseQuery = FormCloseQuery
  PixelsPerInch = 96
  TextHeight = 13
  object Button1: TButton
    Left = 232
    Top = 40
    Width = 75
    Height = 25
    Caption = ‘Button1‘
    TabOrder = 0
    OnClick = Button1Click
  end
  object TrayIcon1: TTrayIcon
    OnClick = TrayIcon1Click
    Left = 160
    Top = 104
  end
end