技術篇的第9章 [ModalDll] CalendarLib.dpr

library CalendarLib;    uses
  ShareMem,
  SysUtils,
  Classes,
  DLLFrm in 'DLLFrm.pas' {DLLForm};    exports
  ShowCalendar;
  
begin
end. 

DLLFrm.pas

unit DLLFrm;    interface    uses
  SysUtils, WinTypes, WinProcs, Messages, Classes, Graphics, Controls,
  Forms, Dialogs, Grids, Calendar;    type      TDLLForm = class(TForm)
    calDllCalendar: TCalendar;
    procedure calDllCalendarDblClick(Sender: TObject);
  end;    { Declare the export function }
function ShowCalendar(AHandle: THandle; ACaption: String): TDateTime; StdCall;    implementation
{$R *.DFM}    function ShowCalendar(AHandle: THandle; ACaption: String): TDateTime;
var
  DLLForm: TDllForm;
begin
  // Copy application handle to DLL's TApplication object
  Application.Handle := AHandle;
  DLLForm := TDLLForm.Create(Application); 
  try
    DLLForm.Caption := ACaption;
    DLLForm.ShowModal;
    Result := DLLForm.calDLLCalendar.CalendarDate; // Pass the date back in Result
  finally
    DLLForm.Free;
  end;
end;    procedure TDLLForm.calDllCalendarDblClick(Sender: TObject);
begin
  Close;
end;    end. 

MainFfm.pas

unit MainFfm;    interface    uses
  SysUtils, WinTypes, WinProcs, Messages, Classes, Graphics, Controls,
  Forms, Dialogs, StdCtrls;    type
  { First, define a procedural data type, this should reflect the
    procedure that is exported from the DLL. }
  TShowCalendar = function (AHandle: THandle; ACaption: String): TDateTime; StdCall;      { Create a new exception class to refect a failed DLL load }
  EDLLLoadError = class(Exception);      TMainForm = class(TForm)
    lblDate: TLabel;
    btnGetCalendar: TButton;
    procedure btnGetCalendarClick(Sender: TObject);
  end;    var
  MainForm: TMainForm;    implementation    {$R *.DFM}    procedure TMainForm.btnGetCalendarClick(Sender: TObject);
var
  LibHandle   : THandle;
  ShowCalendar: TShowCalendar;
begin      { Attempt to load the DLL }
  LibHandle := LoadLibrary('CALENDARLIB.DLL');
  try
    { If the load failed, LibHandle will be zero.
      If this occurs, raise an exception. }
    if LibHandle = 0 then
      raise EDLLLoadError.Create('Unable to Load DLL');
    { If the code makes it here, the DLL loaded successfully, now obtain
      the link to the DLL's exported function so that it can be called. }
    @ShowCalendar := GetProcAddress(LibHandle, 'ShowCalendar');
    { If the function is imported successfully, then set lblDate.Caption to reflect
      the returned date from the function. Otherwise, show the return raise
      an exception. }
    if not (@ShowCalendar = nil) then
      lblDate.Caption := DateToStr(ShowCalendar(Application.Handle, Caption))
    else
      RaiseLastWin32Error;                                                               
  finally
    FreeLibrary(LibHandle); // Unload the DLL.
  end;
end;    end. 

我是直接拿範例程式執行(有改掉唯讀),執行時按btnGetCalendarClick show一個日期From ,在日期Form上點2下回傳回日期show在MainForm上,值是正常傳回 ,可是會跑出一個0x00000000記憶體不能為read的錯誤訊息.. 於是我在MainForm上use ShareMem,重新complier MainForm(D7),用新的MainForm去執行,值傳回到MainForm上時的錯誤訊息不會出現了,可是在關閉程式出現另一個例外錯誤訊息..軟體例外錯誤(0x0eedfade)於位置0x77e6a4e1..[RunTime Error 217 at 00413DD] 有人可以指點一下嗎??

你的 Project 裡頭也要加 Uses ShareMem;    用 Project -> View Source 看到這個，改成這樣

program Project1;    uses
  ShareMem,
  Forms,
  Unit1 in 'Unit1.pas' {Form1};    {$R *.res}    begin
  Application.Initialize;
  Application.CreateForm(TForm1, Form1);
  Application.Run;
end.

引言: 你的 Project 裡頭也要加 Uses ShareMem; 用 Project -> View Source 看到這個，改成這樣

program Project1;    uses
  ShareMem,
  Forms,
  Unit1 in 'Unit1.pas' {Form1};    {$R *.res}    begin
  Application.Initialize;
  Application.CreateForm(TForm1, Form1);
  Application.Run;
end.

喔,原來ShareMem是加在那裡, 有繼續研究下去的動力了..