调用DLL中的MDI子窗体,怎样判断它是否被创建

Question

找个一在DLL中封装MDI子窗体的例子,可以被调用了,但当再次调用了,又创建另一个同样的子窗体
请问该怎样避免重复创建相同的子窗体啊,
dll的源码如下:
--------------------------------
library jiemian;uses
  SysUtils,
  forms,
  Classes,
  Unit1 in 'Unit1.pas' {Form1};
{$R *.res}
procedure showform;stdcall;
  var
  form:tform1;
  begin
  if form=nil then
    begin
     form:=tform1.Create(application);
     form.show;
    end
      else
      form.BringToFront;
  end;
exports
 showform;
begin
end.

Answer 1

procedure TMainForm.Openmdiwin(Sender: TFormClass);
Var
  iii:Integer;
  Frm:TForm;
begin
    For iii:=0 to MainForm.MDIChildCount-1 Do Begin
        if MainForm.MDIChildren[iii].ClassType=Sender Then Begin
           Frm:=MainForm.MDIChildren[iii];
           if Frm.WindowState=wsMinimized then //為最小化
              ShowWindow(Frm.handle,SW_SHOWNORMAL)
           Else
              ShowWindow(Frm.handle,SW_SHOWNA);
           if (Not Frm.Visible) then Frm.Visible:=True;
           Frm.BringToFront;
           Frm.SetFocus;
           Exit;
        End;
    End;
    Frm:=TForm(Sender.NewInstance);
    Frm:=Frm.Create(Self);
    Frm.Show;
end;把这个函数改到你的dll

Answer 2

var
DLLForm procedure TMainForm.StateMnClick(Sender: TObject);
type
  InvokeDLLForm =function (App: TApplication; Scr: TScreen):TForm;
var
  DLLHandle: THandle;
  DLLSub: InvokeDLLForm;  hp:HWND;
  DllPath:string;
begin
  if Assigned(DLLForm) then DLLForm.Show;
  hp:=0;
  hp:=FindWindow('TMySumForm','工作量统计');
  if hp <> 0 then
  begin
    if IsIconic(hp) then
      ShowWindow(hp, SW_RESTORE)
    else
      BringWindowToTop(hp);
      //SetForegroundWindow(hp);
  end else
  begin
    DllPath:=GetDLLPath('Sum');
    if DllPath='' then  Exit;
    DLLHandle := LoadLibrary(Pchar(DllPath));
    if DLLHandle <> 0 then
    begin
      @DLLSub := GetProcAddress(DLLHandle, 'CreateDLLForm');
      if Assigned(DLLSub) then
      begin
        DLLForm := DLLSub(Application, Screen );
        DLLForm.Show;
      end;
    end;
  end;
end;

Answer 3

同步Screen对象，然后枚举Screen.Forms查找

Answer 4

各位:
我的意思是想把一窗体封装在DLL里,由MDI父窗体调用而创建子窗体. anbangs(大邦) ( ):
怎把你的函数加到DLL啊?我的DLL里没有TMainForm这变量啊.
qinget(C#热恋中) :
你的源码是DLL里面的吗?水平有限,可以解释一下吗

Answer 5

dll代码:调用的时候传入一个Adoconnection就可以了，需要带包编译\\1---ModuleDemo.dpr
library ModuleDemo;{ 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,
  DemoFrm in 'DemoFrm.pas' {DemoForm};{$R *.res}
exports
  CallModule;
begin
end.
\\2---DemoFrm.pas
unit DemoFrm;interfaceuses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs,DB, ADODB, StdCtrls, Buttons, ExtCtrls;type
  TDemoForm = class(TForm)
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
    procedure FormCreate(Sender: TObject);
    procedure SpeedButton1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;var
  DemoForm: TDemoForm;
  procedure CallModule(ss:TADOConnection);stdcall;
implementation{$R *.dfm}
var  AdoConn:Pointer;
procedure CallModule(SS:TADOConnection);
begin
  AdoConn:=SS;
  if not Assigned(DemoForm) then
  DemoForm:=TDemoForm.Create(Application);
  DemoForm.BringToFront;
end;
procedure TDemoForm.FormClose(Sender: TObject; var Action: TCloseAction);
begin
  Action:=cafree;
  DemoForm:=nil;
end;procedure TDemoForm.FormCreate(Sender: TObject);
begin
//
end;procedure TDemoForm.SpeedButton1Click(Sender: TObject);
begin
  close;
end;end.

Answer 6

if not Assigned(DemoForm) then
  DemoForm:=TDemoForm.Create(Application);就是你要的

Answer 7

IF  not  Assigned(DemoForm) then
   DemoForm:= TDemoForm.Create(self)
else
   DemoForm.Show;