使用DLL文件中封装的窗口

徐长友

文章摘要：
     编写软件时常常使用到DLL文件，本文就使用DLL文件中封装的窗口来说说Delphi中在DLL如何封装窗口，如何调用DLL中封装的窗口，及MDI-Child在DLL中载入并使用

一、在DLL中封装窗口
    打开Delphi新建一个DLL工程，保存为usedll，生成代码

library usedll;

{ Important note about DLL memory management: ShareMem must be the
first unit in your library's USES clause AND your project's (select
Project-View Source) USES clause if your DLL exports any procedures or
functions that pass strings as parameters or function results. This
applies to all strings passed to and from your DLL--even those that
are nested in records and classes. ShareMem is the interface unit to
the BORLNDMM.DLL shared memory manager, which must be deployed along
with your DLL. To avoid using BORLNDMM.DLL, pass string information
using PChar or ShortString parameters. }

uses
SysUtils,
Classes;

{$R *.res}

begin
end.

新建一个窗体，添加一个Label和Button，设置如下：

object Form1: TForm1
Left = 192
Top = 133
Width = 334
Height = 221
Caption = 'DLL'#20013#20351#29992#31383#20307
Color = clBtnFace
Font.Charset = DEFAULT_CHARSET
Font.Color = clWindowText
Font.Height = -11
Font.Name = 'MS Sans Serif'
Font.Style = []
OldCreateOrder = False
PixelsPerInch = 96
TextHeight = 13
object Label1: TLabel
Left = 104
Top = 80
Width = 80
Height = 13
Caption = 'DLL'#20013#20351#29992#31383#20307
end
object Button1: TButton
Left = 120
Top = 152
Width = 75
Height = 25
Caption = #30830#23450
TabOrder = 0
OnClick = Button1Click
end
end

添加一过程：procedure LoadForm; export;
procedure LoadForm;
begin
Form1 := TForm1.Create(Application);
try
Form1.ShowModal;
finally
Form1.Free;
end;
end;

全部完整的代码：

library usedll;

uses
SysUtils,
Classes,
Form_Unit in 'Form_Unit.pas' {Form1};

{$R *.res}
exports
LoadForm index 1;
begin

end.

unit Form_Unit;

interface

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

type
TForm1 = class(TForm)
Label1: TLabel;
Button1: TButton;
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;

var
Form1: TForm1;
ApplicationName: String;
procedure LoadForm(Handle: THandle; AppName: ShortString); export;

implementation

{$R *.dfm}
procedure LoadForm(Handle: THandle; AppName: ShortString);
begin
Application.Handle := Handle;
ApplicationName := AppName;
Form1 := TForm1.Create(Application);
try
Form1.ShowModal;
finally
Form1.Free;
end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
self.close;
end;

end.

编译后生成usedll.dll文件，至此DLL文件就完成了

二、调用DLL中封装的窗口

    新建一个工程，添加一个Button，窗体布局如下：

object Form1: TForm1
Left = 192
Top = 133
Width = 336
Height = 222
Caption = 'Form1'
Color = clBtnFace
Font.Charset = DEFAULT_CHARSET
Font.Color = clWindowText
Font.Height = -11
Font.Name = 'MS Sans Serif'
Font.Style = []
OldCreateOrder = False
PixelsPerInch = 96
TextHeight = 13
object Button1: TButton
Left = 128
Top = 88
Width = 75
Height = 25
Caption = #25171#24320#31383#20307
TabOrder = 0
OnClick = Button1Click
end
end

完整的代码如下：

unit Use_Unit;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,Dialogs, StdCtrls;
type
TForm1 = class(TForm)
Button1: TButton;
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;

var
Form1: TForm1;
procedure LoadForm; external 'usedll.dll' index 1;
implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
begin
LoadForm;
end;

end.

三、MDI-Child在DLL中载入并使用
    如果是MDI-Child又如何在DLL中载入并使用呢，下面就这个问题说说使用DLL文件中封装的窗口。
新建一个DLL工程，保存为mdidll，再新建一个窗体，FormStyle设为fsMDIChild，如下：
object Form1: TForm1
Left = 192
Top = 133
Width = 344
Height = 234
Caption = 'MDI'
Color = clBtnFace
Font.Charset = DEFAULT_CHARSET
Font.Color = clWindowText
Font.Height = -11
Font.Name = 'MS Sans Serif'
Font.Style = []
FormStyle = fsMDIChild
OldCreateOrder = False
Position = poDefault
Visible = True
OnClose = FormClose
PixelsPerInch = 96
TextHeight = 13
end

代码如下：

unit mdi_Unit;

interface

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

type
TForm1 = class(TForm)
procedure FormClose(Sender: TObject; var Action: TCloseAction);
private
{ Private declarations }
public
{ Public declarations }
MyParentForm: TForm;
MyParentApplication: TApplication;
end;

var
DllApplication: TApplication;
implementation

{$R *.dfm}

procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
Action:=caFree;
end;

end.

library mdidll;

uses
Windows,
Messages,
SysUtils,
Classes,
Graphics,
Controls,
Forms,
Dialogs,
mdi_Unit in 'mdi_Unit.pas' {Form1};

procedure LoadChild(ParentApplication: TApplication; ParentForm: TForm); export; stdcall;
var
Form1: TForm1;
DllProc: Pointer;

begin
Application:=ParentApplication;
Form1:=TForm1.Create(ParentForm);
Form1.MyParentForm:=ParentForm;
Form1.MyParentApplication:=ParentApplication;
Form1.Show;
end;

procedure DLLUnloadProc(Reason: Integer); register;
begin
if Reason = DLL_PROCESS_DETACH then Application:=DllApplication;
end;

{$R *.res}
exports
LoadChild;
begin
DllApplication:=Application;
DLLProc := @DLLUnloadProc;
end.

编译后生成mdidll.dll文件。
使用DLL中的MDI-Child窗口如下：

    新建一个工程，主窗口设置如下FormStyle设为fsMDIForm：
object Form1: TForm1
Left = 192
Top = 133
Width = 544
Height = 375
Caption = 'Form1'
Color = clBtnFace
Font.Charset = DEFAULT_CHARSET
Font.Color = clWindowText
Font.Height = -11
Font.Name = 'MS Sans Serif'
Font.Style = []
FormStyle = fsMDIForm
Menu = MainMenu1
OldCreateOrder = False
PixelsPerInch = 96
TextHeight = 13
object MainMenu1: TMainMenu
Left = 72
Top = 136
object N1: TMenuItem
Caption = #26032#24314'(&N)'
OnClick = N1Click
end
end
end
代码：

unit usemdi_Unit;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, Menus;

type
TForm1 = class(TForm)
MainMenu1: TMainMenu;
N1: TMenuItem;
procedure N1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;
T_ProvaChild = procedure (ParentApplication: TApplication; ParentForm: TForm); stdcall;
var
Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.N1Click(Sender: TObject);
var
DllHandle: THandle;
ProcAddr: FarProc;
ProvaChild: T_ProvaChild;
begin
DllHandle := LoadLibrary('mdidll');
ProcAddr := GetProcAddress(DllHandle, 'LoadChild');
if ProcAddr <> nil then
begin
ProvaChild := ProcAddr;
ProvaChild(Application,Self);
end;
end;

end.