Question

我正在尝试在服务器（PC）和客户端（Android 应用程序）之间制作一个简单的聊天应用程序。当我从客户端向服务器发送消息时一切正常并且消息显示在 JFrame 上，但是当我从服务器向客户端发送消息时，只有第一条消息有效并到达客户端，而不是以下其他消息。我认为问题出在 Thread 类的 run() 方法内部。

这是客户端代码：

public class MainActivity extends AppCompatActivity {
    EditText editText;
    TextView textView;
    Button button;
    private static Socket s;
    String message="";
    private static String ip="192.168.0.112";
    private static int port=3336;
    String messageReceived="";
    static DataInputStream in;
    static DataOutputStream out;

    @Override
    protected void onStart() {
        super.onStart();
        Log.d("myTag", "App Started");
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        editText=(EditText)findViewById(R.id.editText);
        textView=(TextView)findViewById(R.id.textView);
        button=(Button)findViewById(R.id.button);
    }

    public void send(View v){
        message=editText.getText().toString();
        myTaskSend mt=new myTaskSend();
        mt.execute();
        editText.setText("");
    }

    public void connect(View v){
        myTaskConnect mt2=new myTaskConnect();
        mt2.execute();
    }

    class myTaskSend extends AsyncTask<Void, Void, Void> {

        @Override
        protected Void doInBackground(Void... voids) {
            try{
                Log.d("myTag", "Message Sent: "+message);
                out.writeUTF(message);
                if(message.toLowerCase().equals("exit")){
                    Log.d("myTag", "Connection Closed");
                }
            }catch(Exception e){
                e.printStackTrace();
            }
            return null;
        }
    }

    class myTaskConnect extends AsyncTask<Void, Void, Void> {

        @Override
        protected Void doInBackground(Void... voids) {
            try{

                s=new Socket(ip,port);
                Log.d("myTag", "Connection Successful");
                in=new DataInputStream(s.getInputStream());
                out=new DataOutputStream(s.getOutputStream());
                ReadThread t=new ReadThread();
                t.start();
            }catch(Exception e){
                e.printStackTrace();
            }
            return null;
        }
    }
    
    class ReadThread extends Thread{
        @Override
        public void run() {
            super.run();
            try{
                while(true){
                    messageReceived=in.readUTF();
                    Log.d("myTag", "Message Received: "+messageReceived);
                    textView.setText(textView.getText()+"Server: "+messageReceived+"\n");
                }

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

这是服务器端代码：

public class Server {
    
    static TextArea textArea;
    static TextField textField;
    static ServerSocket ss;
    static Socket s;
    static DataInputStream in;
    static DataOutputStream out;
    static int port=3336;
    private JFrame frame;

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    Server window = new Server();
                    window.frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
        
        String msgin="";
        try {
            System.out.println("Starting the server...");
            ss=new ServerSocket(port);
            System.out.println("Server active on the port: "+port);
            s=ss.accept();
            System.out.println("Connection succesfull");
            ss.close();
            in=new DataInputStream(s.getInputStream());
            out=new DataOutputStream(s.getOutputStream());
            System.out.println("Waiting for a message from the client...");
            while(!msgin.toLowerCase().equals("exit")) {
                msgin=in.readUTF();
                textArea.setText(textArea.getText()+"Client: "+msgin+"\n");
                System.out.println("Message received");
            }
        
            s.close();
            System.out.println("Closing the connection");
            
        }catch(IOException e){
            System.err.println(e);
        }
        
    }
    
    public Server() {
        initialize();
    }
    
    private void initialize() {
        frame = new JFrame("SERVER");
        frame.setBounds(100, 100, 582, 451);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().setLayout(null);
        textArea = new TextArea();
        textArea.setBounds(23, 10, 510, 239);
        frame.getContentPane().add(textArea);
        textField = new TextField();
        textField.setBounds(23, 319, 372, 49);
        frame.getContentPane().add(textField);
        
        JButton button = new JButton("New button");
        frame.getRootPane().setDefaultButton(button);
        button.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                try {
                    String msgout="";
                    msgout=textField.getText().trim();
                    out.writeUTF(msgout);
                    System.out.println("Message sent to the client: "+msgout);
                    textField.setText("");
                }catch(IOException e1) {
                    System.out.println(e1);
                }
            }
        });
        button.setBounds(425, 319, 108, 49);
        frame.getContentPane().add(button);
    }
}

谢谢！

Answer 1

请在向客户端发送数据后尝试方法out.flush();：

out.writeUTF(msgout);
out.flush();
System.out.println("Message sent to the client: "+msgout);

在 JAVA 聊天应用程序中从服务器（PC）向客户端（Android）发送消息的问题

1 个答案: