聊天Java-服務器故障

Question

大家好！

是的，我正在嘗試使用Java進行聊天。 問題是我有兩個班。 一個用於客戶端，另一個用於ClientGUI。 客戶那里擁有邏輯事物，而客戶GUI具有設計。 問題出在第46行，其中new ListenFromServer().start(); 出現錯誤

“無法訪問類型為Controller的封閉實例。必須使用類型為COntroller的封閉實例（eg xnew A（），其中x是Controller的實例）來限定分配。”

我希望有人可以幫助我！

**Controller (Client logic)** 

package Server;

import java.io.*;
import java.net.*;
import java.util.*;




public class Controller {

    private static ObjectInputStream input;
    private static ObjectOutputStream output;
    private static Socket socket;
    private static ClientGUI clientgui;

    private static String username;
    private static String server;
    private static int port;



    public static boolean startClient(){

        try{
            socket = new Socket(server, port);
        }catch (Exception ex){
            System.out.print("Error connecting to the server: " + ex);
            return false;
        }

        String message = "Connection is accepted; " + socket.getInetAddress() +" - "+  socket.getPort();
        System.out.println(message);


    try {
        input=new ObjectInputStream(socket.getInputStream());
        output =new ObjectOutputStream(socket.getOutputStream());
    }
    catch (IOException io) {
        System.out.print("Exception creating new Input/Output Stream: "+ io);
        return false;

    }

    **********new ListenFromServer().start();********* //The problem is here

    try {
        output.writeObject(username);
    }
    catch(IOException io) {
        System.out.print("Exception doing login: " + io);
        disconnect();
        return false;
    }
    return true;
    }

    private void display(String message) {
        if(clientgui == null)
            System.out.println(message);
        else
            clientgui.append(message +"\n");
    }

    public static void sendMessage(Message message) {
        try {
            output.writeObject(message);
        }
        catch(IOException exd) {
            System.out.print("Eceptionwritingtoserver: " + exd);
        }
    }

    private static void disconnect() {
        try {
            if(input != null)
                input.close();
        }catch (Exception ex){}
        try{
            if(output != null)
                output.close();
        }catch(Exception ex){}
        try{
            if(socket != null)
                socket.close();
        }catch(Exception ex){};

        if (clientgui != null)
            clientgui.connectionFailed();
        }

    public class ListenFromServer extends Thread{


        public void run() {
            while(true){
                try{
                    String message = (String) input.readObject();
                    if(clientgui == null){
                        System.out.println(message);
                        System.out.print(":");
                    }
                    else {
                        clientgui.append(message);
                    }
                }
                catch(IOException io){
                    System.out.print("Server has closed the connection");
                    if(clientgui != null)
                        clientgui.connectionFailed();
                    break;
                }
                catch(ClassNotFoundException classex){

                }

                }


            }

        }

    }

ClientGUI

    package Server;
    import javax.swing.*;
    import java.awt.*;
    import java.awt.event.*;


    /*
     * The Client with its GUI
     */
    public class ClientGUI extends JFrame implements ActionListener {

        private static final long serialVersionUID = 1L;

        private JLabel lblusername;

        private JTextField textfieldusername, textfieldserver, textfieldportnumber;

        private JButton btnlogin, btnlogout, btnonline;

        private JTextArea textareamessage;

        private boolean connected;

        private Client client;

        private int defaultPort;
        private String defaultHost;


        ClientGUI(String host, int port) {

            super("Chat Client");
            defaultPort = port;
            defaultHost = host;


            JPanel northPanel = new JPanel(new GridLayout(2,2));
            JPanel serverAndPort = new JPanel(new GridLayout(1,2, 2, 2));
            JLabel lblserveraddress = new JLabel("Server Address:  ");
            JLabel lblchat = new JLabel("                #BallIsLife");
            JLabel lblportnumber = new JLabel("Port Number:  ");

            textfieldserver = new JTextField(host);
            textfieldserver.setHorizontalAlignment(SwingConstants.LEFT);
            textfieldserver.setFont(new Font("Tahoma", Font.PLAIN, 20));
            textfieldportnumber = new JTextField("" + port);
            textfieldportnumber.setFont(new Font("Tahoma", Font.PLAIN, 20));
            textfieldportnumber.setHorizontalAlignment(SwingConstants.LEFT);

            lblserveraddress.setFont(new Font("Tahoma", Font.PLAIN, 19));
            serverAndPort.add(lblserveraddress);
            serverAndPort.add(textfieldserver);
            serverAndPort.add(lblchat);
            serverAndPort.add(lblportnumber);
            serverAndPort.add(textfieldportnumber);
            lblchat.setForeground(Color.RED);
            lblportnumber.setFont(new Font("Tahoma", Font.PLAIN, 19));
            northPanel.add(serverAndPort);
            getContentPane().add(northPanel, BorderLayout.NORTH);

            JPanel panelbtn = new JPanel();
            northPanel.add(panelbtn);


            btnlogin = new JButton("Login");
            panelbtn.add(btnlogin);
            btnlogin.setFont(new Font("Tahoma", Font.PLAIN, 17));
            btnlogin.addActionListener(this);

            btnonline = new JButton("Online");
            panelbtn.add(btnonline);
            btnonline.setFont(new Font("Tahoma", Font.PLAIN, 17));

            btnonline.addActionListener(this);
            btnonline.setEnabled(false);        

            btnlogout = new JButton("Logout");
            panelbtn.add(btnlogout);
            btnlogout.setFont(new Font("Tahoma", Font.PLAIN, 17));
            btnlogout.addActionListener(this);
            btnlogout.setEnabled(false);        

            JButton btnPicture = new JButton("Picture");
            btnPicture.setFont(new Font("Tahoma", Font.PLAIN, 17));
            btnPicture.setEnabled(false);
            panelbtn.add(btnPicture);


            textareamessage = new JTextArea("Welcome to the #BallIsLife Chat room.\n");
            textareamessage.setFont(new Font("Monospaced", Font.PLAIN, 15));

            textareamessage.setLineWrap(true);
            textareamessage.setEditable(false);

            JPanel centerPanel = new JPanel(new GridLayout(1,1));
            JScrollPane scrollPane = new JScrollPane(textareamessage);
            centerPanel.add(scrollPane);
            getContentPane().add(centerPanel, BorderLayout.CENTER);


            JPanel southPanel = new JPanel();
            getContentPane().add(southPanel, BorderLayout.SOUTH);

            lblusername = new JLabel("Enter your username", SwingConstants.CENTER);
            lblusername.setFont(new Font("Tahoma", Font.PLAIN, 15));
            southPanel.add(lblusername);

            textfieldusername = new JTextField("Write your username here.");
            textfieldusername.setFont(new Font("Tahoma", Font.PLAIN, 14));
            textfieldusername.setColumns(50);

            southPanel.add(textfieldusername);


            setDefaultCloseOperation(EXIT_ON_CLOSE);
            setSize(823, 665);
            setVisible(true);

        }

    //Logiken

        void append(String str) {
            textareamessage.append(str);
            textareamessage.setCaretPosition(textareamessage.getText().length() - 1);
        }


        void connectionFailed() {
            btnlogin.setEnabled(true);
            btnlogout.setEnabled(false);
            btnonline.setEnabled(false);
            lblusername.setText("Enter your username");
            textfieldusername.setText("Write your username here");

            textfieldportnumber.setText("" + defaultPort);
            textfieldserver.setText(defaultHost);

            textfieldserver.setEditable(false);
            textfieldportnumber.setEditable(false);

            textfieldusername.removeActionListener(this);
            connected = false;
        }

        //

        public void actionPerformed(ActionEvent e) {
            Object button = e.getSource();

            if(button == btnlogout) {
                Controller.sendMessage(new Message("", Message.LOGOUT)); //Ändra till Chatmessage klass
                btnlogin.setText("Login");
                return;
            }

            if(button == btnonline) {
                Controller.sendMessage(new Message("", Message.ONLINE));    //Ändra till Chatmessage klass          
                return;
            }


            if(connected) {

                Controller.sendMessage(new Message(textfieldusername.getText(), Message.MESSAGE)); //Ändra till Chatmessage klass       
                textfieldusername.setText("");
                return;
            }


            if(button == btnlogin) {

                String username = textfieldusername.getText();

                if(username.length() == 0)
                    return;

                String server = textfieldserver.getText();
                if(server.length() == 0)
                    return;

                String portNumber = textfieldportnumber.getText();
                if(portNumber.length() == 0)
                    return;


                int port = 0;
                try {
                    port = Integer.parseInt(portNumber);
                }
                catch(Exception en) {
                    return;  
                }


                client = new Client(server, username, port, this);

                if(!Controller.startClient()) 
                    return;

                }

                connected = true;

                textfieldusername.setText("");
                btnlogin.setText("Send message");


                btnlogin.setEnabled(true);

                btnlogout.setEnabled(true);
                btnonline.setEnabled(true);

                textfieldserver.setEditable(false);
                textfieldportnumber.setEditable(false);

                textfieldusername.addActionListener(this);
            }



        // to start the whole thing the server
        public static void main(String[] args) {
            new ClientGUI("localhost", 1500);
        }

    }

Answer 1

看看這個嵌套類。 如果嵌套的內部類不是靜態的，則它可以訪問外部對象及其字段。 在這里，內部類有一個Outer.this 。 對於使用new Inner()進行的分配，則必須提供一個Outer對象： outer.new Inner() 。 通常，可能首先嘗試使內部類靜態化，以查看是否需要外部類。

class Outer {

    String s;

    void p() {
        StaticInner x = new StaticInner();
        Inner y = this.new Inner();
    }

    static class StaticInner {

         void f() {
             // CANNOT use field s.
         }
    }

    class Inner {

        int n;

        void g() {
            n;
            this.n;
            this;
            Outer.this;
            Outer.this.s;
            s;
        }
    }
}

---

最簡單的方法是使內部類“靜態”。

public static class ListenFromServer extends Thread{

通常，將刪除所有static對象，並僅創建一個Controller對象。 這樣可以節省打字。