How to bind swing.JTextArea to PrintStream to accept data

java, jtextarea, multithreading, swing, user-interface

Solution

One way is to create a class that links the JTextArea to an OutputStream, say called TextAreaOutputStream, and have it extend OutputStream. Give it a StringBuilder object to hold the String that it is constructing in the `write(int b)` override, and give it a reference to the JTextArea that you want to write text to. Then when a new line character is encountered, write the String to the JTextArea, but be sure to do this on the Swing event thread or EDT.

For example:

import java.io.IOException;
import java.io.OutputStream;

import javax.swing.JTextArea;
import javax.swing.SwingUtilities;

public class TextAreaOutputStream extends OutputStream {

   private final JTextArea textArea;
   private final StringBuilder sb = new StringBuilder();
   private String title;

   public TextAreaOutputStream(final JTextArea textArea, String title) {
      this.textArea = textArea;
      this.title = title;
      sb.append(title + "> ");
   }

   @Override
   public void flush() {
   }

   @Override
   public void close() {
   }

   @Override
   public void write(int b) throws IOException {

      if (b == '\r')
         return;

      if (b == '\n') {
         final String text = sb.toString() + "\n";
         SwingUtilities.invokeLater(new Runnable() {
            public void run() {
               textArea.append(text);
            }
         });
         sb.setLength(0);
         sb.append(title + "> ");

         return;
      }

      sb.append((char) b);
   }
}

Then it is trivial to wrap this in a PrintStream object and have it used by your socket.

Problem

Client has gui and extra thread (to process socket input and print it out to passes object of type PrintStream). The gui form has `new javax.swing.JTextArea()`. I need to pass to thread the object `PrintStream` to write to: `ClientThreadIn(PrintStream inOutput){...}`. How to create/bind gui JTextArea to accept data form `ClientThreadIn` using `PrintStream`? Client: ``` in = new BufferedReader(new InputStreamReader(s.getInputStream())); out = new PrintWriter(new OutputStreamWriter(s.getOutputStream())); ClientThreadIn threadIn = new ClientThreadIn(in, System.out); // client passes it's System.out to thread for writing ``` So JTextArea should be similar to console. It should be able to accept data from Thread (actually Thread writes to PrintStream of gui)... Is there something similar to JTextArea.getInputStream()?

Original source