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The Java Developers Almanac 1.4Order this book from Amazon. |
e988. Implementing a Console Window with a JTextArea ComponentThis example creates a console window using aJTextArea which
shows all output printed to System.out and System.err .
System.out and System.err are replaced with piped io
streams. Two reader threads are created that retrieve the output from
these piped io streams and append it to the JTextArea component.
import java.awt.*; import java.awt.event.*; import java.io.*; import javax.swing.*; import javax.swing.event.*; import javax.swing.text.*; public class Console extends JFrame { PipedInputStream piOut; PipedInputStream piErr; PipedOutputStream poOut; PipedOutputStream poErr; JTextArea textArea = new JTextArea(); public Console() throws IOException { // Set up System.out piOut = new PipedInputStream(); poOut = new PipedOutputStream(piOut); System.setOut(new PrintStream(poOut, true)); // Set up System.err piErr = new PipedInputStream(); poErr = new PipedOutputStream(piErr); System.setErr(new PrintStream(poErr, true)); // Add a scrolling text area textArea.setEditable(false); textArea.setRows(20); textArea.setColumns(50); getContentPane().add(new JScrollPane(textArea), BorderLayout.CENTER); pack(); setVisible(true); // Create reader threads new ReaderThread(piOut).start(); new ReaderThread(piErr).start(); } class ReaderThread extends Thread { PipedInputStream pi; ReaderThread(PipedInputStream pi) { this.pi = pi; } public void run() { final byte[] buf = new byte[1024]; try { while (true) { final int len = pi.read(buf); if (len == -1) { break; } SwingUtilities.invokeLater(new Runnable() { public void run() { textArea.append(new String(buf, 0, len)); // Make sure the last line is always visible textArea.setCaretPosition(textArea.getDocument().getLength()); // Keep the text area down to a certain character size int idealSize = 1000; int maxExcess = 500; int excess = textArea.getDocument().getLength() - idealSize; if (excess >= maxExcess) { textArea.replaceRange("", 0, excess); } } }); } } catch (IOException e) { } } } }The console window is created using try { new Console(); } catch (IOException e) { }
e983. Modifying Text in a JTextArea Component e984. Enumerating the Lines in a JTextArea Component e985. Setting the Tab Size of a JTextArea Component e986. Moving the Focus with the TAB Key in a JTextArea Component e987. Enabling Word-Wrapping and Line-Wrapping in a JTextArea Component
© 2002 Addison-Wesley. |