mainfrm.pas

《Delphi 7经典问题解析》源代码 第一到七章 基础篇源程序 应用篇源程序

unit mainfrm;

interface

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

type
  //定义一个测试线程
  TTestThread = class(TThread)
    procedure Execute; override;
  end;
  TMainForm = class(TForm)
    btnLoadLib: TBitBtn;
    btnFreeLib: TBitBtn;
    BtnCreateThread: TBitBtn;
    BtnFreeThread: TBitBtn;
    lblCount: TLabel;
    procedure btnLoadLibClick(Sender: TObject);
    procedure btnFreeLibClick(Sender: TObject);
    procedure BtnCreateThreadClick(Sender: TObject);
    procedure BtnFreeThreadClick(Sender: TObject);
    procedure FormCreate(Sender: TObject);
  private
    LibHandle: THandle;
    TestThread: TTestThread;
    Counter: integer;
    GoThread: Boolean;
    { Private declarations }
  public
    { Public declarations }
  end;

var
  MainForm: TMainForm;

implementation

{$R *.dfm}

//线程执行过程
procedure TTestThread.Execute;
begin
  while MainForm.GoThread do
  begin
    MainForm.lblCount.Caption := IntTostr(MainForm.Counter);
    Inc(MainForm.Counter);
  end;
end;

procedure TMainForm.FormCreate(Sender: TObject);
begin
  LibHandle := 0;
  TestThread := nil;
end;


//这个过程用于调入动态链接库DLLEntry.dll
procedure TMainForm.btnLoadLibClick(Sender: TObject);
begin
  if LibHandle = 0 then
  begin
    LibHandle := LoadLibrary('DLLEntry.dll');
    if LibHandle = 0 then
      raise Exception.Create('Unable to Load DLL');
  end
  else
    MessageDlg('Library already Loaded', mtWarning, [mbok], 0);
end;

//这个过程用于释放链接库
procedure TMainForm.btnFreeLibClick(Sender: TObject);
begin
  if not (LibHandle = 0) then
  begin
    FreeLibrary(LibHandle);
    LibHandle := 0;
  end;
end;

//创建一个线程
procedure TMainForm.BtnCreateThreadClick(Sender: TObject);
begin
  if TestThread = nil then
  begin
    GoThread := True;
    TestThread := TTestThread.Create(false);
  end;
end;

//释放一个线程
procedure TMainForm.BtnFreeThreadClick(Sender: TObject);
begin
  if not (TestThread = nil) then
  begin
    GoThread := False;
    TestThread.Free;
    TestThread := nil;
    Counter := 0;
  end;
end;
end.