打印机状态变更通知无法接收问题求助（附测试代码）

我想开发一款能在打印机打印时显示提示信息的应用。我写了一个控制台测试程序，但接收不到打印机状态变更的通知。需要说明的是，当我用JOB_NOTIFY_TYPE和JOB_NOTIFY_FIELD_STATUS监控作业状态时，能正常收到通知。

请问打印机是否不会发送状态变更通知？这是否和打印机类型或驱动有关？

测试代码 #

program PrinterMonitor;

{$APPTYPE CONSOLE}

uses
  Winapi.Windows,
  Winapi.WinSpool;

const
  PrinterField: WORD = PRINTER_NOTIFY_FIELD_STATUS;

var
  PrinterName: string;
  hStopEvent: THandle;
  hPrinter: THandle;
  hPrintNotify: THandle;
  pno: TPrinterNotifyOptions;
  pnot: TPrinterNotifyOptionsType;
  pni: Pointer;
  dwChange: DWORD;
  WaitHandles: array[0..1] of THandle;

function CtrlHandler(fdwCtrlType: DWORD): BOOL; stdcall;
begin
  Result := False;
  case fdwCtrlType of
    CTRL_C_EVENT, CTRL_CLOSE_EVENT:
    begin
      SetEvent(hStopEvent);
      Result := True;
    end;
  end;
end;

procedure GetPrinterNotifyData(const Info: TPrinterNotifyInfo);
var
  I: Integer;
begin
  for I := 0 to Info.Count - 1 do
  begin
    with Info.aData[I] do
    begin
      case wType of
        PRINTER_NOTIFY_TYPE:
        begin
          case Field of
            PRINTER_NOTIFY_FIELD_STATUS: WriteLn('Printer status: ', NotifyData.adwData[0]);
          end;
        end;
      end;
    end;
  end;
end;

begin
  if ParamCount < 1 then
  begin
    WriteLn('No printer name specified.');
    Exit;
  end;
  PrinterName := ParamStr(1); //pass a printer name as argument

  OpenPrinter(PWideChar(PrinterName), hPrinter, nil);
  if hPrinter = 0 then
  begin
    WriteLn('Cannot open printer "', PrinterName, '". ErrorCode: ', GetLastError);
    Exit;
  end;

  pnot.wType := PRINTER_NOTIFY_TYPE;
  pnot.Count := 1;
  pnot.pFields := @PrinterField;

  pno.Version := 2;
  pno.Count := 1;
  pno.pTypes := @pnot;

  hStopEvent := CreateEvent(nil, True, False, nil);
  if hStopEvent = 0 then
  begin
    WriteLn('Cannot create stop event. ErrorCode: ', GetLastError);
    ClosePrinter(hPrinter);
    Exit;
  end;

  hPrintNotify := FindFirstPrinterChangeNotification(hPrinter, 0, 0, @pno);
  if hPrintNotify = 0 then
  begin
    WriteLn('Cannot start monitoring. ErrorCode: ', GetLastError);
    ClosePrinter(hPrinter);
    CloseHandle(hStopEvent);
    Exit;
  end;

  WaitHandles[0] := hStopEvent;
  WaitHandles[1] := hPrintNotify;

  SetConsoleCtrlHandler(@CtrlHandler, True); // handling CTRL+C & close console events for stop monitoring

  WriteLn('==== Monitor started ====');
  while True do
  begin
    case WaitForMultipleObjects(2, @WaitHandles, False, INFINITE) of
      WAIT_OBJECT_0: // hStopEvent signalled
      begin
        WriteLn('==== Monitor stopped ====');
        Break;
      end;
      WAIT_OBJECT_0+1: // hPrintNotify signalled
      begin
        if not FindNextPrinterChangeNotification(hPrintNotify, dwChange, nil, pni) then
        begin
          WriteLn('Cannot get notify changes data.');
          Break;
        end;
        GetPrinterNotifyData(PPrinterNotifyInfo(pni)^);
        FreePrinterNotifyInfo(PPrinterNotifyInfo(pni));
      end;
      else
      begin
        WriteLn('Wait failed');
        Break;
      end;
    end;
  end;
  FindClosePrinterChangeNotification(hPrintNotify);
  ClosePrinter(hPrinter);
  CloseHandle(hStopEvent);
end.

回答 #

1. 打印机状态通知的触发逻辑
   打印机状态变更通知并非针对打印作业的提交或完成，而是对应硬件层面的状态变化，比如打印机离线/在线切换、缺纸、卡纸、墨粉耗尽、设备被暂停或恢复等场景。普通的作业流转（如作业开始打印、完成）属于作业状态范畴，不会触发打印机状态的通知。

2. 打印机类型与驱动的影响
   这确实和打印机类型及驱动实现直接相关：

   • 物理打印机：主流品牌的现代驱动会完整实现状态上报，但老旧驱动或第三方兼容性差的驱动可能遗漏部分状态通知逻辑。
   • 虚拟打印机（如PDF打印机、虚拟传真机）：这类设备没有实体硬件状态，驱动通常不会发送打印机状态变更通知，除非特意模拟相关状态。
   • 网络打印机：依赖打印机的网络管理协议（如SNMP）和驱动的适配，如果打印机本身不支持状态上报，或驱动未实现该功能，也无法收到通知。

3. 代码优化建议
   你的代码中FindFirstPrinterChangeNotification的第二个参数（fdwFilter）传了0，虽然通过TPrinterNotifyOptions指定了监控字段，但部分驱动需要明确的过滤器标志才能触发通知。建议修改为：

hPrintNotify := FindFirstPrinterChangeNotification(hPrinter, PRINTER_CHANGE_STATUS, 0, @pno);

另外，可以先调用GetPrinter获取打印机当前的PRINTER_INFO_2结构中的Status字段，确认目标打印机是否存在可触发状态变更的场景（比如手动让打印机离线），以此验证通知机制是否正常。

内容的提问来源于stack exchange，提问作者yonni