java - 需要帮助改进 Java 客户端端口监听器

Question

我有一小段代码在包含 SWING 控件的小程序中运行，用于将信息写入特定端口上的套接字，然后监听响应。这工作正常，但有一个问题。端口监听器本质上处于循环中，直到服务器接收到 null。我希望用户在等待服务器响应时能够在 applet 实例化的 GUI 中执行其他操作(这可能需要几分钟才能发生)。我还需要担心服务器和客户端之间的连接断开。但是按照代码的编写方式，小程序似乎会卡住(实际上是在循环中)，直到服务器响应为止。我怎样才能让监听器在后台进行监听，允许程序中发生其他事情。我假设我需要使用线程并且我确信对于这个应用程序，它很容易实现，但是我缺乏坚实的线程基础阻碍了我。下面是代码(你可以看到它是多么简单)。我怎样才能改进它，让它做我需要它做的事情>

  public String writePacket(String packet) {
/* This method writes the packet to the port - established earlier */
   System.out.println("writing out this packet->"+packet+"<-");
   out.println(packet);
  String thePacket =    readPacket();  //where the port listener is invoked.  
   return thePacket;
   }
    private String readPacket() {
      String thePacket ="";
      String fromServer="";
      //Below is the loop that freezes everything.   
     try {
      while ((fromServer = in.readLine()) != null) { 
        if (thePacket.equals("")) thePacket = fromServer;
        else 
        thePacket = thePacket+newLine+fromServer;
    }
        return thePacket;  //when this happens, all listening should stop.   
   } catch (IOException e) {
        // TODO Auto-generated catch block
    e.printStackTrace();
    return null;
    }

     }  

谢谢，

埃利奥特

Answer 1

有很多不同的方法可以让 IO 在不同的线程上执行，但在这种情况下，您可能想使用 SwingWorker .

你的代码看起来像这样:

private final Executor executor = Executors.newSingleThreadExecutor();

public void writePacket(final String packet) 
{
  // schedules execution on the single thread of the executor (so only one background operation can happen at once)
  //
  executor.execute(new SwingWorker<String, Void>()
      {

        @Override
        protected String doInBackground() throws Exception
        {
          // called on a background thread


          /* This method writes the packet to the port - established earlier */
          System.out.println("writing out this packet->"+packet+"<-");
          System.out.println(packet);
          String thePacket = readPacket();  //where the port listener is invoked.  
          return thePacket;            
        }

        @Override
        protected void done()
        {
          // called on the Swing event dispatch thread


          try
          {
            final String thePacket = get();

            // update GUI with 'thePacket'
          }
          catch (final InterruptedException e)
          {
            // TODO Auto-generated catch block
            e.printStackTrace();
          }
          catch (final ExecutionException e)
          {
            // TODO Auto-generated catch block
            e.printStackTrace();
          } 
        }
      });
}

private String readPacket() 
{
  String thePacket ="";
  String fromServer="";
  //Below is the loop that freezes everything.   
  try 
  {
    while ((fromServer = in.readLine()) != null) 
    { 
      if (thePacket.equals("")) 
        thePacket = fromServer;
      else 
        thePacket = thePacket+newLine+fromServer;
    }
    return thePacket;  //when this happens, all listening should stop.   
  } 
  catch (IOException e) 
  {
    e.printStackTrace();
    return null;
  }
}