复制文件时，如何显示进度条

procedure mycopyfile(sourcef,targetf:string;i:integer);
var
FromF,ToF:file;
NumRead,NumWritten:Integer;
Buf:array[1..2048] of Char;
n:integer;
begin
AssignFile(FromF,sourcef);
Reset(FromF, 1); { Record size = 1 }
AssignFile(ToF,targetf); { Open output file }
Rewrite(ToF, 1); { Record size = 1 }
n:=0;
repeat
BlockRead(FromF, Buf, SizeOf(Buf), NumRead);
form1.ProgressBar1.Position:=sizeof(buf)*n*100 div FileSize(FromF)*i div 4;
application.ProcessMessages;
//显示进度
BlockWrite(ToF, Buf, NumRead, NumWritten);
inc(n);
until (NumRead = 0) or (NumWritten <> NumRead);
form1.ProgressBar1.Position:=100;
CloseFile(FromF);
CloseFile(ToF);
end;
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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 := 0;
setStream.Position := 0;

BufSize := num;
block := BufSize div 100;
GetMem(buf, BufSize);

ProgressBar1.Max := 100;
ProgressBar1.Min := 0;
ProgressBar1.Position := 0;

while num <> 0 do
begin
Application.ProcessMessages;
n := block;
if n > num then n := num;
getStream.ReadBuffer(buf^, n);
setStream.WriteBuffer(buf^, n);
ProgressBar1.Position := Trunc((1 - num / BufSize) * 100);
Dec(num, n);
end;

FreeMem(buf, BufSize);
getStream.Free;
setStream.Free;

ShowMessage('复制完毕');
ProgressBar1.Position := 0;
end;

end.