java - 如何将输入从 GUI 传递到客户端而不是服务器？

Question

我对 Java 很陌生。我有一个程序，它的作用就像客户端和服务器之间的计算器。客户端将像这样输入他们的函数(+ 1 2)。但现在我给它一个 GUI 界面。如何将用户输入从 GUI 传递到客户端控制台，然后将其传递到服务器进行计算，然后将其显示回 UI？我只需要一些简单的东西。

客户端

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

import java.awt.*;        // using AWT containers and components
import java.awt.event.*;  // using AWT events and listener interfaces
import javax.swing.*;

public class mathClient extends JFrame implements ActionListener {
    private int count = 0;
    private JFrame frame;
    private JPanel panel;

    private JLabel lblInput;
    private JLabel lblOutput;
    private JTextField tfInput;
    private JTextField tfOutput;


            /** The entry main() method */
    public static void main(String[] args) throws Exception {
    // Invoke the constructor to setup the GUI, by allocating an instance
        mathClient app = new mathClient();

    }

            public void actionPerformed(ActionEvent event){
                try{
                Socket clientSocket = new Socket("localhost", 50000);
                BufferedReader inFromServer = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
                DataOutputStream outToServer = new DataOutputStream(clientSocket.getOutputStream());
                PrintWriter print = new PrintWriter(clientSocket.getOutputStream(), true);

                String input;
                String output;

                //String input;

                while(true){
                    //System.out.println("Please enter your function and numbers:");
                    input = tfInput.getText();

                    print.println(input);

                    if(input.equals("disconnect")){
                        break;
                    }   

                    output = inFromServer.readLine();
                    System.out.println(output);
                    tfOutput.setText(output);


                }
                clientSocket.close();
                }
                catch (Exception e)
                {
                }


        }


    public mathClient()
    {
        Container contentPane = getContentPane();
        contentPane.setLayout(new BorderLayout());

        JFrame frame = new JFrame("Calculator");
        JPanel panel = new JPanel();

        JLabel lblInput = new JLabel("Input: ");

        JLabel lblOutput = new JLabel("Output: ");    

        JTextField tfInput = new JTextField();
        tfInput.setEditable(true);
    //  tfInput.addActionListener();

        JTextField tfOutput = new JTextField();
        tfOutput.setEditable(false);

        JButton btnCalculate = new JButton("Calculate");
        btnCalculate.addActionListener(this);

        frame.add(panel);
        panel.add(lblInput);
        panel.add(tfInput);
        panel.add(lblOutput);
        panel.add(tfOutput);
        panel.add(btnCalculate);

        tfInput.setPreferredSize(new Dimension(200, 30));
        tfOutput.setPreferredSize(new Dimension(200, 30));

        frame.pack();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(230,250);
        frame.setResizable(false);
        frame.setVisible(true);      
    }

}

服务器

import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Scanner;

// Takes in a mathematical operation and the operands from a client and returns the result
// Valid operations are add, sub, multiply, power, divide, remainder, square 
public class mathServer
{ 
    public static void main(String [] args) throws IOException 
    { 
        ServerSocket welcomeSocket = new ServerSocket(50000); //put server online
        while(true)  
        { 
            System.out.println("Waiting for connection...");
            Socket connectionSocket = welcomeSocket.accept();  //open server to connections
            System.out.println("Connection accepted");
            process(connectionSocket);                    //process accepted connection
            System.out.println("Connection closed");
        } 
    }  

    //BufferedReader(Reader r)
    static void process(Socket welcomeSocket) throws IOException 
    {  
        InputStream in = welcomeSocket.getInputStream(); 
        BufferedReader buffer = new BufferedReader(new InputStreamReader(in)); 
        OutputStream out = welcomeSocket.getOutputStream(); 
        PrintWriter print = new PrintWriter(out, true);       

        String input = buffer.readLine(); //get user input from client                

        while(input != null && !input.equals("disconnect")) //check for input, if bye exit connection
        {              
            int answer = operate(input); //perform desired operation on user input
            print.println(answer);          //print out result
            input = buffer.readLine();       //get next line of input                
        }
        welcomeSocket.close(); 
    }  

    //Talk to the client          
    static int operate(String s) 
    { 
        System.out.println(s); //check if same as client input

        Scanner scanner = new Scanner(s); 
        char option = scanner.next().charAt(0);   //gets desired operation

        System.out.println(option); //checks for correct operation 

        switch (option) { 
            case '+': 
                return (scanner.nextInt() + scanner.nextInt());
            case '-':
                return (scanner.nextInt() - scanner.nextInt());
            case '*':
                return (scanner.nextInt() * scanner.nextInt());
            case '^':
                return (int) Math.pow(scanner.nextInt(), scanner.nextInt());
            case '/':
                return scanner.nextInt() / scanner.nextInt();
            case '%':
                return scanner.nextInt() % scanner.nextInt();
            case 's':
                return (int) Math.pow(scanner.nextInt(), 2);
            default:
                return (int) Math.pow(scanner.nextInt(), 3);
        }                       
    }
}

Answer 1

问题之一是 actionPerformed() 中的 NullPointerException。但是，它不可见，因为您有一个空的 catch block 。永远不应该有空的 catch block 。将其更改为:

catch (Exception e) {
    e.printStackTrace();
}

成员 tfInput 和 tfOutput 在 actionPerformed() 中为 null，因为它们从未初始化。构造函数 mathClient() 分配局部变量 JTextField tfInput 和 JTextField tfInput 并覆盖相关成员。

除了无休止的 while 循环之外，还有其他几个迫在眉睫的问题。您不应该阻止 Swing 的 Event Dispatch Thread带 socket 。考虑使用辅助线程或 SwingWorker。

参见Concurrency in Swing了解详细信息和示例。