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此刻我正在創建一個簡單的聊天程序，它將允許您在服務器之間進行通信。當在另一個文件中的一個文件中使用時，我遇到訪問該用戶名變量的問題。用戶將輸入他的名字，這是在ChatGUI文件中完成的，然後當他進入聊天室時，會創建一個EchoFrame，它位於EchoFrame文件中。同樣在EchoFrame文件中，我希望將用戶名添加到用戶消息中，並且還會在他們連接到聊天室以及他們何時離開聊天室時發佈消息。我希望我清楚地解釋我的問題，還有其他需要的信息請告訴我！小型聊天程序，訪問文件之間的變量
EchoFrame
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.net.*;
public class EchoFrame extends Frame{
EchoPanel ep;
Button sendMessage;
public EchoFrame(){
setSize(500,500);
setTitle("Echo Client");
addWindowListener(new WindowAdapter(){
public void windowClosing(WindowEvent we){
System.exit(0);
}
});
ep = new EchoPanel();
add(ep, BorderLayout.CENTER);
setVisible(true);
}
public static void main(String[] args){
EchoFrame ef = new EchoFrame();
}
}
class EchoPanel extends Panel implements ActionListener, Runnable{
TextField tf;
TextArea ta;
Button connect, disconnect;
Socket s;
BufferedReader br;
PrintWriter pw;
Thread t;
String fromServer;
String username;
public EchoPanel(){
setLayout(new BorderLayout());
tf = new TextField();
tf.setEditable(false);
tf.addActionListener(this);
add(tf, BorderLayout.NORTH);
ta = new TextArea();
ta.setEditable(false);
add(ta, BorderLayout.CENTER);
Panel buttonPanel = new Panel();
connect = new Button("Connect");
connect.addActionListener(this);
buttonPanel.add(connect);
disconnect = new Button("Disconnect");
disconnect.setEnabled(false);
disconnect.addActionListener(this);
buttonPanel.add(disconnect);
add(buttonPanel, BorderLayout.SOUTH);
}
public void actionPerformed(ActionEvent ae){
if(ae.getSource() == connect){
try{
s = new Socket("127.0.0.1", 8189);
ta.append(username + " has entered the chat room. \n");
br = new BufferedReader(new InputStreamReader(s.getInputStream()));
pw = new PrintWriter(s.getOutputStream(), true);
}catch(UnknownHostException uhe){
System.out.println(uhe.getMessage());
}catch(IOException ioe){
System.out.println(ioe.getMessage());
}
t = new Thread(this);
t.start();
tf.setEditable(true);
connect.setEnabled(false);
disconnect.setEnabled(true);
}else if(ae.getSource() == disconnect){
try{
pw.close();
br.close();
s.close();
}catch(IOException ioe){
System.out.println(ioe.getMessage());
}
t = null;
ta.append(username + " has disconnected from chat room. \n");
tf.setEditable(false);
connect.setEnabled(true);
disconnect.setEnabled(false);
}else if(ae.getSource() == tf){
String fromTf = tf.getText();
pw.println(fromTf);
tf.setText("");
}else{
//additional events
}
}
public void run(){
fromServer = "";
try{
while((fromServer = br.readLine()) != null){
ta.append(username + ":" + fromServer + "\n");
}
}catch(IOException ioe){
System.out.println(ioe.getMessage());
}
}
}
ChatGUI
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.net.*;
import java.awt.BorderLayout;
import java.awt.CardLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
public class ChatGUI extends JFrame {
private int currentCard = 1;
private JPanel cardPanel;
private CardLayout cl;
JTextField usernameField;
String username;
public ChatGUI() {
setTitle("Chat Program");
setSize(500, 120);
cardPanel = new JPanel();
cl = new CardLayout();
cardPanel.setLayout(cl);
JPanel chooseUsername = new JPanel();
JLabel usernameLabel = new JLabel("Please enter your username:");
chooseUsername.add(usernameLabel);
cardPanel.add(chooseUsername, "Log in");
usernameField = new JTextField(15);
usernameField.setEditable(true);
add(usernameField, BorderLayout.CENTER);
JPanel buttonPanel = new JPanel();
JButton logInBtn = new JButton("Enter Chat Room");
buttonPanel.add(logInBtn);
logInBtn.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
currentCard = 2;
cl.show(cardPanel, "" + (currentCard));
username = usernameField.getText(); //gets username
EchoFrame ef = new EchoFrame(); //creates message room
}
});
getContentPane().add(cardPanel, BorderLayout.NORTH);
getContentPane().add(buttonPanel, BorderLayout.SOUTH);
}
public static void main(String[] args) {
ChatGUI cl = new ChatGUI();
cl.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
cl.setVisible(true);
}
}
聊天服務器
import java.io.*;
import java.net.*;
import java.util.*;
public class ChatServer{
Socket s;
ArrayList <ChatHandler>handlers;
public ChatServer(){
try{
ServerSocket ss = new ServerSocket(8189);
handlers = new ArrayList<ChatHandler>();
for(;;){
s = ss.accept();
new ChatHandler(s, handlers).start();
}
}catch(IOException ioe){
System.out.println(ioe.getMessage());
}
}
public static void main(String[] args){
ChatServer tes = new ChatServer();
}
}
聊天處理器
import java.io.*;
import java.net.*;
import java.util.*;
public class ChatHandler extends Thread{
Socket s;
BufferedReader br;
PrintWriter pw;
String temp;
ArrayList <ChatHandler>handlers;
public ChatHandler(Socket s, ArrayList <ChatHandler>handlers){
this.s = s;
this.handlers = handlers;
}
public void run(){
try{
handlers.add(this);
br = new BufferedReader(new InputStreamReader(s.getInputStream()));
pw = new PrintWriter(s.getOutputStream(), true);
temp = "";
while((temp = br.readLine()) != null){
for (ChatHandler ch : handlers){
ch.pw.println(temp);
}
System.out.println(temp);
}
}catch(IOException ioe){
System.out.println(ioe.getMessage());
}finally{
handlers.remove(this);
}
}
}
http://stackoverflow.com/help/mcve – nullpointer