如何在不冻结JFrame并等待动作监听器完成的情况下从动作监听器调用方法？

Question

How do I set the text of a JTextArea while its JFrame is running, and refresh the JFrame to show the change, from another class?

I have a JFrame with a JTextArea which acts as a log, and the string it prints i update periodically with new activity from another class. My JFrame class (EnablePage) looks like this:

package bot;
import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.JTextArea;
import javax.swing.JScrollPane;
import javax.swing.JButton;
import javax.swing.JLabel;
import java.awt.Font;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
public class EnablePage extends JFrame {
    public static String enablePane;
    private static JPanel contentPane;
    public static JTextArea txtrHello = new JTextArea();

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    EnablePage frame = new EnablePage();
                    frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }
    public EnablePage() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(100, 100, 594, 474);
        contentPane = new JPanel();
        contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
        setContentPane(contentPane);
        contentPane.setLayout(null);
        JScrollPane scrollPane = new JScrollPane();
        scrollPane.setToolTipText("");
        scrollPane.setBounds(6, 89, 582, 357);
        contentPane.add(scrollPane);
        txtrHello.setEditable(false);
        txtrHello.setText(enablePane);
        txtrHello.setWrapStyleWord(true);
        txtrHello.setLineWrap(true);
        scrollPane.setViewportView(txtrHello);

        JButton btnNewButton = new JButton("Enable");
        btnNewButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                try {
                    navigator.navigator();
                } catch (Exception e1) {
                    e1.printStackTrace();
                }
            }
        });
        btnNewButton.setBounds(59, 29, 117, 29);
        contentPane.add(btnNewButton);
    }
    public static void update(String x) {
        txtrHello.setText(enablePane+"\n"+x);

    }
}

And from my navigator class I've been trying to use this line of code to update the JtextArea, while it manipulates a website. This code I didn't include, but replaced here with "Thread.sleep(100000);" to illustrate the problem:

 package bot;


    import java.text.DateFormat;
    import java.text.SimpleDateFormat;
    import java.util.Date;

    import javax.swing.JOptionPane;

    public class navigator {

        public static DateFormat dateFormat = new SimpleDateFormat("MM-dd-yyyy(HH:mm:ss)");
        public static void navigator() throws Exception {
            Date date1 = new Date();
Thread.sleep(100000);


    EnablePage.update("Bot enabled: "+dateFormat.format(date1));
                 }
        }

However this is not updating the JFrame with the new text, because the EnablePage class is stuck waiting for the navigator() method to complete. What ends up happening is the Enable button stays blue because the actionlistener method is never broken from, because the nagivator() method never finished. What can I do to still call navigator() from the enable button but not have the EnablePage class freeze on this line?

Answer 1

JTextArea#append will allow you to append text to the JTextArea , both setText and append are bound methods, this means that they will trigger an update when they are called so you shouldn't need to do anything more. If it's not updating then it sounds like you have a reference issue.

You should consider providing a fully runnable example which demonstrates your problem. This will result in less confusion and better responses

You should avoid the use of static , especially when associated with UI components, as this really begins to give you trouble with what you are referencing and what's on the screen. static is NOT a cross communication mechanism for objects and shouldn't be used as such.

If you can, you should define some kind of interface which describes the actions which be executed on your log frame (ie addLog(String) ), have your log frame implement this interface and then pass a reference of it to those classes that need it.

Alternatively, you could use a singleton pattern to allow your log window to be accessed from any where in your application, personally, I'd be tempted to devise a queue of some kind, where other classes pushed log events onto this (singleton) queue and you had your frame either poll it or use some kind of blocking queue mechanism to monitor for changes to the queue. This would require you to have a separate Thread (or SwingWorker ) which monitored the queue in the background so you don't block the Event Dispatching Thread.

Avoid using null layouts, pixel perfect layouts are an illusion within modern ui design. There are too many factors which affect the individual size of components, none of which you can control. Swing was designed to work with layout managers at the core, discarding these will lead to no end of issues and problems that you will spend more and more time trying to rectify

Updated

Your runnable example works for me, more or less. Your reliance on static is worrying and Thread.sleep(100000); will block the Event Dispatching Thread, making your program look like it's hung (cause it has). The following is reworked version of your example, without null layouts, without static and using a Swing Timer instead of Thread.sleep . The great thing about this, is once you press the "Enable" button, the timer will update the text area every second...

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.Timer;

public class EnablePage extends JFrame {

    private JTextArea txtrHello = new JTextArea(10, 20);

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    EnablePage frame = new EnablePage();
                    frame.pack();
                    frame.setLocationRelativeTo(null);
                    frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    public EnablePage() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        setLayout(new BorderLayout());

        JScrollPane scrollPane = new JScrollPane(txtrHello);
        scrollPane.setToolTipText("");
        add(scrollPane);
        txtrHello.setEditable(false);
        txtrHello.setWrapStyleWord(true);
        txtrHello.setLineWrap(true);

        JButton btnNewButton = new JButton("Enable");
        btnNewButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                try {
                    Navigator.navigator(EnablePage.this);
                } catch (Exception e1) {
                    e1.printStackTrace();
                }
            }
        });
        add(btnNewButton, BorderLayout.NORTH);
    }

    public void update(String x) {
        System.out.println("Update " + x + "\n");
        txtrHello.append(x);

    }

    public static class Navigator {

        public static DateFormat dateFormat = new SimpleDateFormat("MM-dd-yyyy(HH:mm:ss)");

        public static void navigator(EnablePage page) throws Exception {

            Timer timer = new Timer(1000, new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    Date date1 = new Date();
                    page.update("Bot enabled: " + dateFormat.format(date1));
                }
            });
            timer.start();
        }
    }
}

Answer 2

Here's a simple example. A clock JTextField is updated from a Thread.

As you can see, there are no update, validate, or invalidate method calls.

Edited to add: The calls to the SwingUtilities invokeLater method are important, to ensure that the Swing components are created and updated on the Event Dispatch thread (EDT) .

I also modified the Clock example to stop the Timer thread cleanly before disposing of the JFrame.

package com.ggl.testing;

import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;

public class Clock implements Runnable {

    private JFrame frame;

    private JTextField clockDisplay;

    private Timer timer;

    @Override
    public void run() {
        frame = new JFrame("Clock");
        frame.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
        frame.addWindowListener(new WindowAdapter() {
            @Override
            public void windowClosing(WindowEvent event) {
                exitProcedure();
            }
        });

        JPanel panel = new JPanel();

        clockDisplay = new JTextField(12);
        clockDisplay.setEditable(false);
        clockDisplay.setHorizontalAlignment(JTextField.CENTER);

        panel.add(clockDisplay);

        frame.add(panel);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);

        timer = new Timer(this);
        new Thread(timer).start();
    }

    public void exitProcedure() {
        timer.setRunning(false);
        frame.dispose();
        System.exit(0);
    }

    public void setText(String text) {
        clockDisplay.setText(text);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Clock());
    }

    public class Timer implements Runnable {

        private volatile boolean running;

        private Clock clock;

        private SimpleDateFormat timeFormat;

        public Timer(Clock clock) {
            this.clock = clock;
            this.running = true;
            this.timeFormat = new SimpleDateFormat("h:mm:ss a");
        }

        @Override
        public void run() {
            while (running) {
                displayTime();
                sleep();
            }

        }

        public void displayTime() {
            Calendar calendar = Calendar.getInstance();
            Date date = calendar.getTime();
            final String s = timeFormat.format(date);
            SwingUtilities.invokeLater(new Runnable() {
                @Override
                public void run() {
                    clock.setText(s);
                }
            });
        }

        public void sleep() {
            try {
                Thread.sleep(200L);
            } catch (InterruptedException e) {
            }
        }

        public synchronized void setRunning(boolean running) {
            this.running = running;
        }

    }

}