有点难，怎么判断网络上的文件是否存在？

不知道是在局域网里吗?
FileExists("绝对路径") //比如"\\192.168.0.193\fff\fff.txt"下面是别人一个在线更新的代码，看看有没帮助呢？
unit update_f;interfaceuses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, TFlatGroupBoxUnit, TFlatButtonUnit, StdCtrls,
  TFlatSpeedButtonUnit, TFlatEditUnit, TFlatMemoUnit, Psock, NMHttp,ShellAPI;type
  TSimpleVersion=record
    dwProductVersionMS: DWORD;
    dwProductVersionLS: DWORD;
  end;
  TUpdate=record      { Structure of update information }
    Name:String[63];
    Version:TSimpleVersion;
    Date:TDate;
    URL1:ShortString;
    URL2:ShortString;
    Update_Info:String;
  end;
  Tupdate_v = class(TForm)
    FlatGroupBox2: TFlatGroupBox;
    FlatGroupBox3: TFlatGroupBox;
    FlatButton1: TFlatButton;
    FlatButton2: TFlatButton;
    Label1: TLabel;
    Label2: TLabel;
    Label3: TLabel;
    Label4: TLabel;
    Label5: TLabel;
    FlatMemo2: TFlatMemo;
    FlatEdit1: TFlatEdit;
    FlatSpeedButton1: TFlatSpeedButton;
    NMHTTP1: TNMHTTP;
    Label6: TLabel;
    Label7: TLabel;
    FlatMemo1: TFlatMemo;
    Label8: TLabel;
    Label9: TLabel;
    Label10: TLabel;
    FlatSpeedButton2: TFlatSpeedButton;
    FlatEdit2: TFlatEdit;
    procedure FlatButton2Click(Sender: TObject);
    procedure NMHTTP1Connect(Sender: TObject);
    procedure NMHTTP1ConnectionFailed(Sender: TObject);
    procedure NMHTTP1Disconnect(Sender: TObject);
    procedure NMHTTP1HostResolved(Sender: TComponent);
    procedure NMHTTP1Status(Sender: TComponent; Status: String);
    procedure FlatButton1Click(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure FlatSpeedButton1Click(Sender: TObject);
    procedure FlatSpeedButton2Click(Sender: TObject);
  private
    { Private declarations }
    Update_New, Update_Ori: TUpdate;
    function AnalyseUpdate(Body: String; var Update: TUpdate): Boolean;
    procedure DisplaySuggestion(b: Boolean);
  public
    { Public declarations }
  end;var
  update_v: Tupdate_v;implementation
const update_text='http://127.0.0.1/update.txt';
{$R *.dfm}//取得当前使用版本的信息
function GetBuildInfo(FName:string):TSimpleVersion;
var
  VerInfoSize: DWORD;
  VerInfo: Pointer;
  VerValueSize: DWORD;
  VerValue: PVSFixedFileInfo;
  Dummy: DWORD;
begin
  VerInfoSize := GetFileVersionInfoSize(PChar(FName), Dummy);
  GetMem(VerInfo, VerInfoSize);
  GetFileVersionInfo(PChar(ParamStr(0)), 0, VerInfoSize, VerInfo);
  VerQueryValue(VerInfo, '\', Pointer(VerValue), VerValueSize);
  with VerValue^ do
  begin
    Result.dwProductVersionMS := dwFileVersionMS;
    Result.dwProductVersionLS := dwFileVersionLS;
  end;
  FreeMem(VerInfo, VerInfoSize);
end;function SeparateVerStr(s:String):TSimpleVersion;
const
  Separator = '.';
var
  p:WORD;
  v1,v2,v3,v4:WORD;
begin
  if Length(s)=0 then Exit;  p:=pos(Separator, s);
  v1:=StrToInt(copy(s,1,p-1));
  Delete(s,1,p);
  p:=Pos(Separator,s);
  v2:=StrToInt(copy(s,1,p-1));
  Delete(s,1,p);
  p:=Pos(Separator,s);
  v3:=StrToInt(copy(s,1,p-1));
  Delete(s,1,p);
  v4:=StrToInt(s);
  Result.dwProductVersionMS:=v1*$10000+v2;
  Result.dwProductVersionLS:=v3*$10000+v4;
end;function Tupdate_v.AnalyseUpdate(Body:String;var Update:TUpdate):Boolean;
var
  TmpStr,Ver:String;
  function CenterStr(Src:String;Before,After:String):String;
  var
    Pos1,Pos2:WORD;
  begin
    Pos1:=Pos(Before,Src)+Length(Before);
    Pos2:=Pos(After,Src);
    Result:=Copy(Src,Pos1,Pos2-Pos1);
  end;
begin
  TmpStr:=CenterStr(Body,Format('[%s]',[LowerCase(Update_Ori.Name)]),Format('[/%s]',[LowerCase(Update_Ori.Name)]));
  if TmpStr='' then Result:=False
  else
  begin
    Ver:=CenterStr(TmpStr,'<ver>','</ver>');
    Update.Version:=SeparateVerStr(Ver);
    Update.Date:=StrToDate(CenterStr(TmpStr,'<date>','</date>'));
    Update.URL1:=CenterStr(TmpStr,'<url1>','</url1>');
    Update.URL2:=CenterStr(TmpStr,'<url2>','</url2>');
    Update.Update_Info:=CenterStr(TmpStr,'<info>','</info>');
    Result:=True;
    FlatMemo1.Lines.Add('最新版本：'+Ver);
    FlatMemo1.Lines.Add('发布日期：'+DateToStr(Update.Date));
    FlatMemo1.Lines.Add('下载地址1：'+Update.URL1);
    FlatMemo1.Lines.Add('下载地址2：'+Update.URL2);
  end;
end;{ Compare tow versions whether need update, True stand for need }
function VersionCheck(OriVer,NewVer:TSimpleVersion):Boolean;
begin
  if (OriVer.dwProductVersionMS=NewVer.dwProductVersionMS) then
    Result:=OriVer.dwProductVersionLS<NewVer.dwProductVersionLS
  else Result:=OriVer.dwProductVersionMS<NewVer.dwProductVersionMS;
end;procedure Tupdate_v.DisplaySuggestion(b:Boolean);
begin
  FlatMemo1.Lines.Add('');
  FlatMemo1.Lines.Add('青苔提示：');
  if b then
  begin
    if VersionCheck(Update_Ori.Version,Update_New.Version) then
      FlatMemo1.Lines.Add('找到一个更新的版本')
   else
      FlatMemo1.Lines.Add('对不起，青苔还未发布更新版本');
  end else
  begin
    FlatMemo1.Lines.Add('查找版本更新情况失败，');
    FlatMemo1.Lines.Add('请检查该版本是否正常，');
    FlatMemo1.Lines.Add('或系统是否连上了Internet。');
  end;
end;procedure Tupdate_v.FlatButton2Click(Sender: TObject);
begin
  Close;
end;procedure Tupdate_v.NMHTTP1Connect(Sender: TObject);
begin
  FlatMemo1.Lines.Add('已连接……');
end;procedure Tupdate_v.NMHTTP1ConnectionFailed(Sender: TObject);
begin
  FlatMemo1.Lines.Add('连接失败！');
end;procedure Tupdate_v.NMHTTP1Disconnect(Sender: TObject);
begin
  FlatMemo1.Lines.Add('断线中……');
end;procedure Tupdate_v.NMHTTP1HostResolved(Sender: TComponent);
begin
  FlatMemo1.Lines.Add('正在解析地址……');
end;procedure Tupdate_v.NMHTTP1Status(Sender: TComponent; Status: String);
begin
  FlatMemo1.Lines.Add(Status);
  If NMHTTP1.ReplyNumber = 404 then
    FlatMemo1.Lines.Add('更新文档没找到……');
end;procedure Tupdate_v.FlatButton1Click(Sender: TObject);
begin
  FlatMemo1.Clear;
  FlatMemo1.Lines.Add('系统消息：');
  FlatMemo1.Lines.Add('开始查看更新信息……');
  NMHTTP1.InputFileMode := FALSE;
  NMHTTP1.OutputFileMode := FALSE;
  NMHTTP1.ReportLevel := Status_Basic;
  try
    NMHTTP1.Get(update_text);
    FlatMemo1.Lines.Add('');
    FlatMemo1.Lines.Add('开始分析……');
    if AnalyseUpdate(NMHTTP1.Body,Update_New) then
    begin
      Label6.Caption:=Format('%d.%d.%d.%d',[
        Update_New.Version.dwProductVersionMS shr 16,
        Update_New.Version.dwProductVersionMS and $FFFF,
        Update_New.Version.dwProductVersionLS shr 16,
        Update_New.Version.dwProductVersionLS and $FFFF
        ]);
      FlatEdit1.Text:=Update_New.URL1;
      FlatEdit2.Text:=Update_New.URL2;
      Label7.Caption:=DateToStr(Update_New.Date);
      FlatMemo2.Lines.Add(Update_New.Update_Info);
      FlatMemo1.Lines.Add('已经分析成功！');
      DisplaySuggestion(True);
    end else
    begin
      FlatMemo1.Lines.Add('不能找到更新信息！');
      FlatMemo1.Lines.Add('分析失败！');
      DisplaySuggestion(False);
    end;
  except
    DisplaySuggestion(False);
    Application.MessageBox('程序更新失败！','提示',MB_OK);
  end;
end;procedure Tupdate_v.FormCreate(Sender: TObject);
begin
  Update_Ori.Name:='mosstools';
  Update_Ori.Version:=GetBuildInfo(ParamStr(0));
  Label8.Caption:=Format('%d.%d.%d.%d',[
    Update_Ori.Version.dwProductVersionMS shr 16,
    Update_Ori.Version.dwProductVersionMS and $FFFF,
    Update_Ori.Version.dwProductVersionLS shr 16,
    Update_Ori.Version.dwProductVersionLS and $FFFF
    ]);
end;procedure Tupdate_v.FlatSpeedButton1Click(Sender: TObject);
begin
  if FlatEdit1.Text<>'' then
    ShellExecute(Handle,nil,PChar(FlatEdit1.Text),nil,nil,SW_SHOWNORMAL);
end;procedure Tupdate_v.FlatSpeedButton2Click(Sender: TObject);
begin
  if FlatEdit2.Text<>'' then
    ShellExecute(Handle,nil,PChar(FlatEdit2.Text),nil,nil,SW_SHOWNORMAL);
end

调试易

有点难，怎么判断网络上的文件是否存在？

解决方案 »