与Java套接字编程一起使用的观察者模式不起作用 [英] Observer Pattern used with Java socket programing not working
问题描述
当我尝试根据来自服务器的数据更新客户端视图时，我的Observer模式出现问题.
I have a problem with my Observer pattern when I'm trying to update the client view based on the data that comes from the server.
将消息发送到客户端的代码:
The code that sends messages to the client:
package model;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
public class PlayerThread extends Thread{
private BufferedReader inFromClient;
private PrintWriter outToClient;
private Socket socket;
public PlayerThread(Socket socket) throws IOException{
this.socket = socket;
inFromClient = new BufferedReader(new InputStreamReader(socket.getInputStream()));
outToClient = new PrintWriter(socket.getOutputStream(), true);
outToClient.println("Hey");
}
public void run(){
// needs to be implemented
}
}
负责在客户端接收数据的代码:
The code that takes care of recieving data on the client side:
package connection;
import java.io.BufferedReader;
import mediator.ModelManager;
public class ClientRecieverThread extends Thread {
private ModelManager model;
private BufferedReader inFromServer;
public ClientRecieverThread(ModelManager model, BufferedReader inFromServer) {
this.model = model;
this.inFromServer = inFromServer;
}
@Override
public void run() {
String message = null;
try {
while (true) {
message = inFromServer.readLine();
//System.out.println(message);
model.setMessage(message);
}
} catch (Exception e) {
}
}
}
以及包含我在客户端使用的观察者模式的代码:
and the code that contains the observer pattern that I use on the client side:
package model;
public class MessageHandler {
private String message;
public MessageHandler(){
message = "Welcome";
}
public void setMessage(String message){
this.message = message;
}
public String getMessage(){
return this.message;
}
}
package mediator;
import java.io.IOException;
import java.net.UnknownHostException;
import java.util.Observable;
import model.MessageHandler;
import connection.Proxy;
public class ModelManager extends Observable{
private MessageHandler messageHandler;
private Proxy proxy; // establish the connection with the server
public ModelManager() throws UnknownHostException, IOException{
proxy = new Proxy(this);
messageHandler = new MessageHandler();
}
public synchronized void setMessage(String message){
setChanged();
messageHandler.setMessage(message);
notifyObservers(message);
}
public String getMessage(){
return messageHandler.getMessage();
}
public void send(String message){
proxy.send(message);
}
}
package view;
import java.awt.BorderLayout;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.util.Observable;
import java.util.Observer;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingConstants;
import model.Board;
public class View extends JPanel implements Observer{
private JFrame frame;
private Board board;
private Rectangle[][] squares;
private JLabel messageLabel;
public View(){
initComponents();
initVariables();
addComponents();
}
private void initComponents() {
frame = new JFrame("TicTacToe");
frame.setSize(500, 500);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLocationRelativeTo(null);
messageLabel = new JLabel("");
messageLabel.setHorizontalAlignment(SwingConstants.CENTER);
messageLabel.setVerticalAlignment(SwingConstants.CENTER);
this.setSize(300,300);
}
private void initVariables() {
board = new Board(3,3, 100);
squares = new Rectangle[board.getRow()][board.getCol()];
for (int i = 0; i < squares.length; i++){
for (int j = 0; j < squares[i].length; j++){
squares[i][j] = new Rectangle();
}
}
}
private void addComponents() {
frame.add(messageLabel, BorderLayout.NORTH);
frame.add(this);
frame.setVisible(true);
}
private void drawBoard(Graphics g, Board board) {
int positionX = this.getWidth()/2 - (board.getCellSize() + board.getCellSize()/2);
int positionY = 50;
Graphics2D g2d = (Graphics2D) g;
for (int i = 0; i < board.getRow(); i++) {
for (int j = 0; j < board.getCol(); j++) {
squares[i][j] = new Rectangle(positionX, positionY, 100, 100);
positionX += 100;
g2d.draw(squares[i][j]);
}
positionY += board.getCellSize();
positionX = this.getWidth()/2 - (board.getCellSize() + board.getCellSize()/2);
}
}
public void paintComponent(Graphics g){
drawBoard(g, board);
}
public void update(Observable o, Object arg) {
System.out.println((String)arg);
}
}
ModelManager和View之间的连接是在Controller类中完成的，就像这样(model.addObserver(view));
The connection between the ModelManager and the View is done in the Controller class like this (model.addObserver(view));
问题是，尽管客户端已接收到数据，但我不理解为什么视图无法更新.
The prolem is that I don't understand why the view doesn't get updated, although the data gets recieved by the client.
先谢谢您！ :)
推荐答案
更改模型时，需要调用方法notifyObservers();，这将通知已添加到模型的观察者.
You need to call the method notifyObservers(); when the model is changed, this is will notify the observers added to the model.
因此在setMessage(String message)内部，进行编码:
So inside the setMessage(String message), do the coding:
if(this.message!=message){
this.message = message;
notifyObservers();
}
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