为什么IDFTP放在线程里就连接不上服务器？

Question

主代码如下：unit Main;interfaceuses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, StrUtils;type
  TFrm_Main = class(TForm)
    Button1: TButton;
    Label1: TLabel;
    procedure Button1Click(Sender: TObject);
  private
    TFtp:array[1..5] of TThread;
    function CreateDestFileUrl(dirs:TStringList;dirroot:string):string;
    function UrlToFtpDir(Url:string):string;
    function SplitString(const Source,ch:string):TStringList;
  public
    { Public declarations }
  end;var
  Frm_Main: TFrm_Main;implementationuses ThreadFTP;{$R *.dfm}function TFrm_Main.SplitString(const Source,ch:string):TStringList;  //把一个字符串拆分成一个字符列表
var temp:String;
    i:Integer;
begin
  Result:=TStringList.Create;
  try
   if Source='' then exit;
   temp:=Source;
   i:=pos(ch,Source);
   while i<>0 do
     begin
       Result.add(copy(temp,0,i-1));
       Delete(temp,1,i);
       i:=pos(ch,temp);
     end;
   Result.add(temp);
  except
    showmessage('分解字符出错'+Source);
  end;
end;function TFrm_Main.UrlToFtpDir(Url:string):string;
var i:integer;
begin
  try
   if Url='' then exit;
   Url:=trim(Url);
   i:=pos(':',Url);
   Delete(Url,i,1);
   Result:=AnsiReplaceText(Url,'\','/');
  except
   showmessage('转换出错');
  end;
end;function TFrm_Main.CreateDestFileUrl(dirs:TStringList;dirroot:string):string;
var i:integer;
    DestFile:string;
begin
  try
    DestFile:=dirroot;
    for i:=1 to dirs.Count-1 do
      begin
       DestFile:=DestFile+'\'+dirs.Strings[i];
      end;
    Result:=DestFile;
  except
    showmessage('获取目的文件路径出错');
  end;  
end;
procedure TFrm_Main.Button1Click(Sender: TObject);
var TIP,TUser,TPassword,TDfile,TDirroot,Url:string;
    TPort:integer;
    TDirs:TStringlist;
begin
  TIP:='60.191.244.136';
  TUser:='blues';
  TPassword:='beginlove';
  TPort:=210;
  TDirroot:='E:';
  Url:=UrlToFtpDir('G:\MOV_3\MOV\KB\SLEEPING_WITH_THE_DEAD\A.RM');
  TDirs:=SplitString(Url,'/');
  TDfile:=CreateDestFileUrl(TDirs,TDirroot);
  TFtp[1]:=MyThreadFtp.Create(False,TIP,TPort,TUser,TPassword,TDirs,TDfile,TDirroot);
end;end.

Answer 1

线程代码如下：unit ThreadFTP;interfaceuses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, IdBaseComponent,  IdFTPCommon,IdComponent, IdTCPConnection,  IdTCPClient,
  IdFTP, StdCtrls, StrUtils;type
  MyThreadFtp = class(TThread)
  private
    fPort:integer;
    fIP,fUser,fPassword,fDfile,fDirroot:string;
    fDirs:TStringList;
    fFtp:TIdFTP;
    function FtpConnect(IP:string;Port:integer;User:string;Password:string):Boolean;
    function FtpDisConnect():Boolean;
    function FtpChangeDir(var Dirs:TStringList):Boolean;
    function FtpGetFile(var Dirs:TStringList;Dfile:string;Dirroot:string):Integer;
             {Result=0:下载成功
              Result=1:服务器上文件获取出错
              Result=2:服务器上文件不存在
              Result=3:已经有完整的影片
              Result=4:断点下载出错
              Result=5:文件校验出错
              Result=6:创建目录出错
              Result=7:下载过程出错
              Result=8:部分下载
              Result=9:下载失败
              }    function CreateDestFileUrl(Dirs:TStringList;Dirroot:string):string;
  protected
    procedure Execute; override;
    procedure ReturnResult();
  public
    constructor Create(CreateSuspended:Boolean;IP:string;Port:integer;User:string;Password:string;Dirs:TStringList;Dfile:string;Dirroot:string);
  published  end;  var n:integer;implementationuses Main;constructor MyThreadFtp.Create(CreateSuspended:Boolean;IP:string;Port:integer;User:string;Password:string;Dirs:TStringList;Dfile:string;Dirroot:string);
begin
  FreeOnTerminate:=true;
  fIP:=IP;
  fPort:=Port;
  fUser:=User;
  fPassword:=Password;
  fDirs:=Dirs;
  fDfile:=Dfile;
  fDirroot:=Dirroot;
  fFtp:=TIdFTP.Create(nil);
  inherited Create(CreateSuspended);
end;function MyThreadFtp.FtpConnect(IP:string;Port:integer;User:string;Password:string):Boolean;
begin
  with fFtp do
   try
    Host:=IP;
    Port:=Port;
    Username:=User;
    Password:=Password;
    Passive:=True;
    ASCIIFilter:=False;
    TransferType:=ftBinary;
    Connect;
   except
    Result:=False;
   end;
    Result:=True;
end;function MyThreadFtp.FtpDisConnect():Boolean;
begin
  try
   fFtp.Disconnect;
  except
   Result:=False;
  end;
   Result:=True;
end;function MyThreadFtp.FtpChangeDir(var Dirs:TStringList):Boolean;
var i:integer;
begin
  for i:=0 to Dirs.Count-2 do
    begin
      try
        fFTP.ChangeDir(Dirs.Strings[i]);
      except
        begin//改变目录时出错
          Result:=False;
          showmessage('改变目录时出错');
          exit;
        end;
      end;
    end;
  Result:=True;
end;function MyThreadFtp.FtpGetFile(var Dirs:TStringList;Dfile:string;Dirroot:string):Integer;
var tempath:string;
    i:integer;
    fs: TSearchRec;
    FileSize,ResumeSize:longint;
begin
 try
   FileSize:=fFTP.Size(dirs.Strings[dirs.Count-1]);
   if FileSize<1 then
     begin
       Result:=1;
       showmessage('服务器上文件获取出错');
       exit;
     end;
 except
     begin
      Result:=2;
      showmessage('服务器上文件不存在');
      exit;
     end;
 end; if FindFirst(dfile,faAnyFile,fs)=0 then
   begin //如果文件存在
     ResumeSize:=FileSize-fs.Size;
     FindClose(fs);
     if ResumeSize=0 then
       begin//已经有完整的影片
         Result:=3;
         exit;
       end
     else if ResumeSize>0 then
       begin//断点下载
         try
           fFTP.Get(dirs.Strings[dirs.Count-1],dfile,false,true);
         except
           begin
             Result:=4;
             showmessage('断点下载出错');
             exit;
           end;
         end;
       end
     else
       begin//文件校验出错
         Result:=5;
         showmessage('文件校验出错');
         exit;
       end;
   end
 else //文件不存在
   begin
     tempath:=dirroot;
     for i:=1 to dirs.Count-2 do
       begin
         tempath:=tempath+'\'+dirs.Strings[i];
         try
           CreateDir(tempath);
         except //创建目录时出错
           begin
             Result:=6;
             showmessage('创建目录时出错');
             exit;
           end;
         end;
       end;
     try
       fFTP.Get(dirs.Strings[dirs.Count-1],dfile);
     except
       begin
         Result:=7;
         showmessage('下载过程出错');
         exit;
       end;
     end;
   end;
//判断文件是否下载成功
 if FindFirst(dfile,faAnyFile,fs)=0 then
   begin
     if fs.Size=FileSize then
       Result:=0 //下载成功
     else
       Result:=8; //部分下载
       FindClose(fs);
   end
 else
   Result:=9; //下载失败
end;function MyThreadFtp.CreateDestFileUrl(Dirs:TStringList;Dirroot:string):string;
var i:integer;
    DestFile:string;
begin
  try
    DestFile:=Dirroot;
    for i:=1 to Dirs.Count-1 do
      begin
       DestFile:=DestFile+'\'+Dirs.Strings[i];
      end;
    Result:=DestFile;
  except
    showmessage('获取目的文件路径出错');
  end;
end;
{ Important: Methods and properties of objects in visual components can only be
  used in a method called using Synchronize, for example,      Synchronize(UpdateCaption);  and UpdateCaption could look like,    procedure ThreadFtp.UpdateCaption;
    begin
      Form1.Caption := 'Updated in a thread';
    end; }{ ThreadFtp }procedure MyThreadFtp.ReturnResult();
begin
  Frm_Main.Label1.Caption:=inttostr(n);
end;procedure MyThreadFtp.Execute;
begin
  FtpConnect(fIP,fPort,fUser,fPassword);
  FtpChangeDir(fDirs);
  n:=FtpGetFile(fDirs,fDfile,fDirroot);
  FtpDisConnect;
  Synchronize(ReturnResult);
  fFtp.Free;
end;end.本想实现多线程下载多个文件，但下载第一个就出现问题，同样的一些代码以主FORM 的 IDFTP 控件 就能实现，各位大侠帮忙看一下