怎样实现'即刷即打'?

Question

我现在用
printer.Canvas.TextRect(Rect,1,1,pristr)
要到最后调用printer.EndDoc才能把内容都打印出来.怎样实现超市那种刷一个条码就打印出相关内容呢?

Answer 1

procedure posprt(billstr:string);
var
    f,OutFile:textfile;
begin
   OutFile:=ExtractFilepath(Application.ExeName)+'output.txt';
   AssignFile(F, OutFile);
   Rewrite(F);
   Writeln(F,'----------------------------------------');
   Writeln(F,'      名称      数量   单价   折扣  金额');
   Writeln(F,'----------------------------------------');  //销售数据准备
   CloseFile(f);
   PrintFile(Outfile); 
end;
procedure PrintFile(AFileToPrint: string);
var
    Port, FileToPrint: TextFile;
    ALine: string;
begin
     AssignFile(FileToPrint, AFileToPrint);
     Reset(FileToprint);
     AssignFile(Port, 'LPT1');
     Rewrite(Port);
     while not Eof(FileToPrint) do
     begin
       Readln(FileToPrint, ALine);
       Writeln(Port, ALine);
     end;
     CloseFile(Port);
     CloseFile(FileToPrint);
end;