这是我正在使用的代码(不是我的代码)
import java.io.*;
import java.net.*;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class SimpleChatClient {
JTextArea incoming;
JTextField outgoing;
BufferedReader reader;
PrintWriter writer;
Socket sock;
public void go() {
JFrame frame = new JFrame("Ludicrously Simple Chat Client");
JPanel mainPanel = new JPanel();
incoming = new JTextArea(15, 50);
incoming.setLineWrap(true);
incoming.setWrapStyleWord(true);
incoming.setEditable(false);
JScrollPane qScroller = new JScrollPane(incoming);
qScroller.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
qScroller.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_ALWAYS);
outgoing = new JTextField(20);
JButton sendButton = new JButton("Send");
sendButton.addActionListener(new SendButtonListener());
mainPanel.add(qScroller);
mainPanel.add(outgoing);
mainPanel.add(sendButton);
frame.getContentPane().add(BorderLayout.CENTER, mainPanel);
setUpNetworking();
Thread readerThread = new Thread(new IncomingReader());
readerThread.start();
frame.setSize(650, 500);
frame.setVisible(true);
}
private void setUpNetworking() {
try {
sock = new Socket("127.0.0.1", 5000);
InputStreamReader streamReader = new InputStreamReader(sock.getInputStream());
reader = new BufferedReader(streamReader);
writer = new PrintWriter(sock.getOutputStream());
System.out.println("networking established");
}
catch(IOException ex)
{
ex.printStackTrace();
}
}
public class SendButtonListener implements ActionListener {
public void actionPerformed(ActionEvent ev) {
try {
writer.println(outgoing.getText());
writer.flush();
}
catch (Exception ex) {
ex.printStackTrace();
}
outgoing.setText("");
outgoing.requestFocus();
}
}
public static void main(String[] args) {
new SimpleChatClient().go();
}
class IncomingReader implements Runnable {
public void run() {
String message;
try {
while ((message = reader.readLine()) != null) {
System.out.println("client read " + message);
incoming.append(message + "\n");
}
} catch (IOException ex)
{
ex.printStackTrace();
}
}
}
}
我的问题是在传入的读者课程中
为什么这一行---- while ((message = reader.readLine()) != null)
永远不会返回null?
据说,线程去检查这一行,另一方面没有客户端的消息,那么上面的行不应该返回null吗?
有人可以解释一下发生了什么吗?我知道套接字连接和所有 我只是想知道收到传入消息的情况。
答案 0 :(得分:1)
您正在使用阻塞功能,例如BufferedReader.readLine()。这将阻止,直到有东西要读。它不会“检查设备并在没有返回任何内容时返回null”。
您可以使用BufferedReader.available()检查是否有任何传入数据,如果结果是>则调用readLine()。 0.