java - 接收通过网络发送的 PDU，并在显示给用户之前按接收到的方式过滤它们

Question

我有以下 Java 方法，我试图用它来过滤通过网络接收的 PDU 消息，并只向用户显示符合过滤条件的 PDU:

public static void displayFilteredPdu(){
    try{
        EspduReceiver.socket = new MulticastSocket(EspduSender.PORT);
        EspduReceiver.address = InetAddress.getByName(EspduSender.DEFAULT_MULTICAST_GROUP);
        EspduReceiver.socket.joinGroup(EspduReceiver.address); 



        while(EspduReceiver.stopCapture == false){
            byte buffer[] = new byte[EspduReceiver.MAX_PDU_SIZE];
            EspduReceiver.packet = new DatagramPacket(buffer, buffer.length);

            EspduReceiver.socket.receive(EspduReceiver.packet);

            Pdu pdu = EspduReceiver.pduFactory.createPdu(EspduReceiver.packet.getData());

            if(pdu != null){
                System.out.print("Got PDU of type: " + pdu.getClass().getName());
                if(pdu instanceof EntityStatePdu){
                    EntityID eid = ((EntityStatePdu)pdu).getEntityID(); 
                    Vector3Double position = ((EntityStatePdu)pdu).getEntityLocation(); 
                    System.out.println(" EID:[" + eid.getSite() + ", " + eid.getApplication() + ", " + eid.getEntity() + "] ");
                    System.out.println("Location in DIS coordinates: [" + position.getX() + ", " + position.getY() + ", " + position.getZ() + "] ");
                    /*Add PDU to ArrayList of PDUs */
                    EspduReceiver.espdu.add(pdu);
    /*              System.out.println(" PDU added to arrayList. "); 
                    System.out.println(espdu); /*This is printing out the actual DIS messages (i.e. edu.nps.moves.dis.EntityState...),
                    maybe try adding the 'eid.getSite()', etc to an ArrayList instead. Use Associative arrays/ map/ hashmap */

                //  if(eid.getSite() != 0){
                        Filter.sitesToBeFiltered.add(eid.getSite());
                        System.out.println("Entity Site added to ArrayList. ");
                //  } else if(eid.getApplication() != 0){
                    Filter.applicationsToBeFiltered.add(eid.getApplication());
                    System.out.println("Entity Application added to ArrayList. ");
                    Filter.IDsToBeFiltered.add(eid.getEntity());
                    System.out.println("Entity ID added to ArrayList");
                    Filter.positionsToBeFilteredX.add(position.getX());
                    System.out.println("Entity X position added to ArrayList. ");
                    Filter.positionsToBeFilteredY.add(position.getY());
                    System.out.println("Entity Y position added to ArrayList. ");
                    Filter.positionsToBeFilteredZ.add(position.getZ());
                    System.out.println("Entity Z position added to ArrayList. ");

                    int i;
                    getFilterConditions();
                    for(i = 0; i < sitesToBeFiltered.size(); i++){
                        if(sitesToBeFiltered.get(i) == filter1Value){
                            //public double xPos = new Double();
                            Gui.displayFilteredOutput.append("\n");
                            Gui.displayFilteredOutput.append("EID: [" + sitesToBeFiltered.get(i) + ", " + applicationsToBeFiltered.get(i) + ", " + IDsToBeFiltered.get(i) + "]. ");
                            double filteredX = positionsToBeFilteredX.get(i);
                            double filteredY = positionsToBeFilteredY.get(i);
                            double filteredZ = positionsToBeFilteredZ.get(i);
                            //Vector3Double filteredEntityPosition = 
                            Gui.displayFilteredOutput.append("\n Location in DIS coordinates: [" + filteredX + ":" + filteredY + ":" + filteredZ + "]. ");
                        }
                    }
                }
            }
        }   
    }
    catch(Exception e){
        System.out.println(e);
        e.printStackTrace();
        System.out.println("Error in displayFilteredPdu() method. ");
        /*09/04/2014 @ 17:100
         * If this exception gets called, presumably it either means that pdu is not an instance of EntityStatePdu, or
         * that pdu does not actually hold a packet.  */
    }

}

这个方法目前在一个名为 Filter.java 的类中，当用户单击 GUI 上的“过滤器”按钮时调用，并将继续调用直到变量 stopCapture 更改为 false(当用户单击 GUI 上的“停止”按钮时会发生这种情况)。

但是，调用时它的表现并不像我希望的那样:目前，当用户单击“过滤器”按钮时，将显示所有 System.out.println 语句在控制台中，显然正在输入 while 循环，但我没有在 GUI 中看到任何显示，我认为这表明 for 循环位于未进入 while 循环的结尾...而且 GUI 停止响应...

据我了解，GUI 停止响应的原因可能是因为我当前使用的是单线程程序，因此将此 displayFilteredPdu() 方法移动到另一个线程可能会阻止 GUI 崩溃，然后我可以使用该方法处理其他问题。

我尝试将方法移动到另一个类(称为 FilteredPdu.java)，它扩展了 Filter，并更改按钮 ActionListener() 以从新类调用方法，即FilteredPdu.displayFilteredPdu();，但我仍然遇到与 GUI 崩溃相同的问题。

知道这是为什么吗？

Answer 1

我认为将它移到另一个类中仍然会导致您的程序陷入无限循环。尝试创建一个扩展线程类，将显示过滤器 pdu 方法设置为:

这是新的线程类:

public class YourThreadClass  extends Thread{
    String fake_input_in_thread = null;

    public YourThreadClass(String fake_input){
        //constructor
        //save the input / whatever you need to pass in from the other class here, and use it later
        fake_input_in_thread = fake_input
    }

    public void run() {
        //your filter code
        try{
            //now you can use the value pass-in from you main class. This should display "testing123" in console.
            System.out.println(fake_input_in_thread);

            EspduReceiver.socket = new MulticastSocket(EspduSender.PORT);
            EspduReceiver.address = InetAddress.getByName(EspduSender.DEFAULT_MULTICAST_GROUP);
            EspduReceiver.socket.joinGroup(EspduReceiver.address); 
            .............................
    }

    //put the below method into the thread class
    public void endOfFilter(){
        EspduReceiver.stopCapture = false;
    }
}

当您的 GUI 需要触发该方法时，这就是您的主类的样子

//initialize 
YourThreadClass thread = null;

public static void displayFilteredPdu(){
    if(thread ==null){
        //This string is to demostrate how you'd pass variables into your custom class, does not have any actual use
        String str = "testing123";

        thread = new YourThreadClass(str);
        thread.start();
    }
}

//in main code
public static void stopFilteredPdu(){
    if(thread != null){
        thread.endOfFilter();
        thread = null;
    }
}