模式窗体与非模式窗体

unit Main;
 
interface
 
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls,ModalForm,ModalessForm;
 
type
  TForm8 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    procedure Button2Click(Sender: TObject);
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;
 
var
  Form8: TForm8;
 
implementation
 
{$R *.dfm}
 
procedure TForm8.Button1Click(Sender: TObject);
begin
  try
    Form9:=TForm9.Create(Application);
    Form9.ShowModal;
  finally
    Form9.Free; //窗体的清理放在同一代码段的try...finaally中，而不是在ModalForm中的Destroy方法里。
    Form9:=nil;
  end;
 
end;
 
procedure TForm8.Button2Click(Sender: TObject);
begin
  if not Assigned(Form10) then  //防止出现多个窗体实例
  Form10:=TForm10.Create(Application); //窗体的创建方式
 
  Form10.Show;
end;
 
end.

unit ModalForm;
 
interface
 
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs;
 
type
  TForm9 = class(TForm)
  private
    { Private declarations }
  public
    { Public declarations }
  end;
 
var
  Form9: TForm9;
 
implementation
 
{$R *.dfm}
 
 
end.

unit ModalessForm;
 
interface
 
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs;
 
type
  TForm10 = class(TForm)
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
    procedure FormDestroy(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;
 
var
  Form10: TForm10;
 
implementation
 
{$R *.dfm}
 
procedure TForm10.FormClose(Sender: TObject; var Action: TCloseAction);
begin
  Action:=caFree;
end;
 
procedure TForm10.FormDestroy(Sender: TObject);
begin
  Form10:=nil; //这里是Form10设为nil而不是TForm10，否则将无法再次创建窗体。
end;
 
end.