复制文件时，如何显示进度条（使用BlockRead函数读取数据，并插入application.ProcessMessages）

procedure mycopyfile(sourcef,targetf:string;i:integer);
var
       FromF,ToF:file;
       NumRead,NumWritten:Integer;
       Buf:array[..] of Char;
       n:integer;
begin
         AssignFile(FromF,sourcef);
         Reset(FromF,    ); {    Record    size    =    1    }
         AssignFile(ToF,targetf); {    Open    output    file    }
         Rewrite(ToF,    ); {    Record    size    =    1    }
         n:=;
         repeat
                   BlockRead(FromF,    Buf,    SizeOf(Buf),    NumRead);
                   form1.ProgressBar1.Position:=sizeof(buf)*n*    div    FileSize(FromF)*i div ;
                   application.ProcessMessages;
                   //显示进度
                   BlockWrite(ToF,    Buf,    NumRead,    NumWritten);
                   inc(n);
           until    (NumRead    =    )    or    (NumWritten    <>    NumRead);
           form1.ProgressBar1.Position:=;
           CloseFile(FromF);
           CloseFile(ToF);
end; 

完整代码：

以下例子是关于delphi复制文件，加上进度条的方法的例子的关键代码:
procedure TForm1.Button1Click(Sender: TObject);
const
  getPath = 'c:/temp/get.rar';
  setPath = 'c:/temp/set.rar';
var
  getStream,setStream: TFileStream;
  num, n: Integer;
  buf: PByte;
  BufSize,block: Integer;
begin
  if not FileExists(getPath) then
  begin
    ShowMessage('源文件不存在');
    Exit;
  end;
  getStream := TFileStream.Create(getPath, fmOpenRead or fmShareExclusive);
  setStream := TFileStream.Create(setPath, fmCreate);
  num := getStream.Size;
  setStream.Size := num;
  getStream.Position := ;
  setStream.Position := ;
  BufSize := num;
  block := BufSize div ;
  GetMem(buf, BufSize);
  ProgressBar1.Max := ;
  ProgressBar1.Min := ;
  ProgressBar1.Position := ;
  while num <>  do
  begin
    Application.ProcessMessages;
    n := block;
    if n > num then n := num;
    getStream.ReadBuffer(buf^, n);
    setStream.WriteBuffer(buf^, n);
    ProgressBar1.Position := Trunc(( - num / BufSize) * );
    Dec(num, n);
  end;
  FreeMem(buf, BufSize);
  getStream.Free;
  setStream.Free;
  ShowMessage('复制完毕');
  ProgressBar1.Position := ;
end;
end.

http://blog.csdn.net/shuaihj/article/details/6129551