e778. 在JList中加入和删除项

The default model for a list does not allow the addition and removal of items. The list must be created with a DefaultListModel.

    // Create a list that allows adds and removes
    DefaultListModel model = new DefaultListModel();
    JList list = new JList(model);
    
    // Initialize the list with items
    String[] items = {"A", "B", "C", "D"};
    for (int i=0; i<items.length; i++) {
        model.add(i, items[i]);
    }
    
    // Append an item
    int pos = list.getModel().getSize();
    model.add(pos, "E");
    
    // Insert an item at the beginning
    pos = 0;
    model.add(pos, "a");

This method replaces an it

 
 
Home > List of Packages > javax.swing.text [49 examples] > JTextArea [7 examples]

 

e988. 用文本域实现一个控制台窗口

This example creates a console window using a JTextArea 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) {
    }

 

Related Example
posted @ 2018-09-06 08:43  Borter  阅读(214)  评论(0)    收藏  举报