Java Threads not working properly with JTextArea
In Java I am building a registration / registration program at the moment (hoping to expand it in the future) but ran into a problem.
I am trying to make text displayable on screen in an animation type style.
When I run the main method of the class the text is displayed just fine, when I run it in the keylistener it fails and waits for the text to appear then updates the frame so I can see it.
Source code below:
Login.class
public class Login implements KeyListener {
int BACK_WIDTH = java.awt.Toolkit.getDefaultToolkit().getScreenSize().width;
int BACK_HEIGHT = java.awt.Toolkit.getDefaultToolkit().getScreenSize().height;
JFrame back_frame = new JFrame();
LoginTerminal login = new LoginTerminal();
public Login() {
back_frame.setSize(BACK_WIDTH, BACK_HEIGHT);
back_frame.setLocation(0, 0);
back_frame.getContentPane().setBackground(Color.BLACK);
back_frame.setUndecorated(true);
//back_frame.setVisible(true);
back_frame.addKeyListener(this);
login.addKeyListener(this);
login.setLocationRelativeTo(null);
login.setVisible(true);
login.field.addKeyListener(this);
login.slowPrint("Please login to continue...\n"
+ "Type 'help' for more information.\n");
}
public void keyPressed(KeyEvent e) {
int i = e.getKeyCode();
if(i == KeyEvent.VK_ESCAPE) {
System.exit(0);
}
if(i == KeyEvent.VK_ENTER) {
login.slowPrint("\nCommands\n"
+ "-----------\n"
+ "register\n"
+ "login\n");
}
}
public void keyReleased(KeyEvent e) {}
public void keyTyped(KeyEvent e) {}
}
LoginTerminal.class
public class LoginTerminal implements KeyListener {
CustomFrame frame = new CustomFrame(Types.TERMINAL);
JTextArea log = new JTextArea();
public JTextField field = new JTextField();
public void setVisible(boolean bool) {
frame.setVisible(bool);
}
public void addKeyListener(KeyListener listener) {
frame.addKeyListener(listener);
}
public void slowPrint(String str) {
for(int i = 0; i < str.length(); i++) {
log.append("" + str.charAt(i));
try {
Thread.sleep(50);
} catch (InterruptedException e) {
e.printStackTrace();
}
if (i == str.length() - 1) {
log.append("\n");
}
}
}
public void setLocation(int x, int y) {
frame.setLocation(x, y);
}
public void setLocationRelativeTo(Component c) {
frame.setLocationRelativeTo(c);
}
public LoginTerminal() {
try {
InputStream is = LoginTerminal.class.getResourceAsStream("/fonts/dungeon.TTF");
Font font = Font.createFont(Font.TRUETYPE_FONT, is);
font = font.deriveFont(Font.PLAIN, 10);
frame.add(field);
frame.add(log);
log.setBackground(Color.BLACK);
log.setForeground(Color.WHITE);
log.setWrapStyleWord(true);
log.setLineWrap(true);
log.setBounds(4, 20 + 4, frame.getWidth() - 8, frame.getHeight() - 50);
log.setFont(font);
log.setEditable(false);
log.setCaretColor(Color.BLACK);
field.setBackground(Color.BLACK);
field.setForeground(Color.WHITE);
field.setBounds(2, frame.getHeight() - 23, frame.getWidth() - 5, 20);
field.setFont(font);
field.setCaretColor(Color.BLACK);
field.addKeyListener(this);
field.setText(" > ");
} catch (FontFormatException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
public void dumpToLog() {
log.append(field.getText() + "\n");
field.setText(" > ");
}
public void keyPressed(KeyEvent e) {
int i = e.getKeyCode();
if(i == KeyEvent.VK_ENTER && field.isFocusOwner()) {
if(field.getText().equals(" > HELP") || field.getText().equals(" > help")) {
dumpToLog();
} else {
dumpToLog();
}
}
if(!field.getText().startsWith(" > ")) {
field.setText(" > ");
}
}
public void keyReleased(KeyEvent e) {}
public void keyTyped(KeyEvent e) {}
}
Main.class
public class Main {
public static void main(String[] args) {
new Login();
}
}
My problem is here:
public Login() {
login.slowPrint("Please login to continue...\n"
+ "Type 'help' for more information.\n");
}
When I run this, it works as expected.
If below in the same class (Login.class)
public void keyPressed(KeyEvent e) {
int i = e.getKeyCode();
if(i == KeyEvent.VK_ENTER) {
login.slowPrint("\nCommands\n"
+ "-----------\n"
+ "register\n"
+ "login\n");
}
}
It hangs and waits for completion.
I think it might be Thread.sleep (50); in LoginTerminal.class, as the title is because this is what triggers the input animation.
I hope I clarified here. Thanks for helping everyone!
EDIT
This is what causes the timer error ...
public void timerPrint(String text) {
Timer timer = new Timer(50, new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
if (index < text.length() - 1 && index >= 0) {
String newChar = Character.toString(text.charAt(index));
textArea.append(newChar);
index++;
} else {
textArea.setText(null);
index = 0;
// You could stop the timer here...
}
}
});
timer.start();
}
Timer constructor (int, new ActionListener () {}) - undefined
EDIT EDIT, whole class:
package com.finn.frametypes;
import java.awt.Color;
import java.awt.Component;
import java.awt.Font;
import java.awt.FontFormatException;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.event.ActionEvent;
import java.io.IOException;
import java.io.InputStream;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.Timer;
import com.finn.gui.CustomFrame;
import com.finn.gui.Types;
public class LoginTerminal implements KeyListener {
CustomFrame frame = new CustomFrame(Types.TERMINAL);
JTextArea log = new JTextArea();
public JTextField field = new JTextField();
public void setVisible(boolean bool) {
frame.setVisible(bool);
}
public void addKeyListener(KeyListener listener) {
frame.addKeyListener(listener);
}
public void timerPrint(String text) {
Timer timer = new Timer(50, new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
if (index < text.length() - 1 && index >= 0) {
String newChar = Character.toString(text.charAt(index));
textArea.append(newChar);
index++;
} else {
textArea.setText(null);
index = 0;
// You could stop the timer here...
}
}
});
timer.start();
}
public void slowPrint(String str) {
for(int i = 0; i < str.length(); i++) {
log.append("" + str.charAt(i));
try {
Thread.sleep(50);
} catch (InterruptedException e) {
e.printStackTrace();
}
if (i == str.length() - 1) {
log.append("\n");
}
}
}
public void setLocation(int x, int y) {
frame.setLocation(x, y);
}
public void setLocationRelativeTo(Component c) {
frame.setLocationRelativeTo(c);
}
public LoginTerminal() {
try {
InputStream is = LoginTerminal.class.getResourceAsStream("/fonts/dungeon.TTF");
Font font = Font.createFont(Font.TRUETYPE_FONT, is);
font = font.deriveFont(Font.PLAIN, 10);
frame.add(field);
frame.add(log);
log.setBackground(Color.BLACK);
log.setForeground(Color.WHITE);
log.setWrapStyleWord(true);
log.setLineWrap(true);
log.setBounds(4, 20 + 4, frame.getWidth() - 8, frame.getHeight() - 50);
log.setFont(font);
log.setEditable(false);
log.setCaretColor(Color.BLACK);
field.setBackground(Color.BLACK);
field.setForeground(Color.WHITE);
field.setBounds(2, frame.getHeight() - 23, frame.getWidth() - 5, 20);
field.setFont(font);
field.setCaretColor(Color.BLACK);
field.addKeyListener(this);
field.setText(" > ");
} catch (FontFormatException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
public void dumpToLog() {
log.append(field.getText() + "\n");
field.setText(" > ");
}
public void keyPressed(KeyEvent e) {
int i = e.getKeyCode();
if(i == KeyEvent.VK_ENTER && field.isFocusOwner()) {
if(field.getText().equals(" > HELP") || field.getText().equals(" > help")) {
dumpToLog();
} else {
dumpToLog();
}
}
if(!field.getText().startsWith(" > ")) {
field.setText(" > ");
}
}
public void keyReleased(KeyEvent e) {}
public void keyTyped(KeyEvent e) {}
}
ANSWER
If anyone is reading this in the future and wants to use slow typing in Java use below:
int index;
public void timerPrint(final String text) {
Timer timer = new Timer(50, new ActionListener() {
public void actionPerformed(ActionEvent e) {
if (index < text.length() - 1 && index >= 0) {
String newChar = Character.toString(text.charAt(index));
textarea.append(newChar);
index++;
} else {
index = 0;
((Timer)e.getSource()).stop();
}
}
});
timer.start();
}
+3
user3636058
source
to share
1 answer
Swing is a single-threaded framework, meaning anything that blocks a Thread Dispatching Thread will prevent the UI from updating or your program to respond to new threads.
See Concurrency in Swing for details .
You should never do blocking ( Thread.sleep
) or long running processes from EDT.
Swing is also NOT thread safe, which means you should never update the UI outside of the EDT context.
This leaves you with a mystery ...
Fortunately, there are options. Probably the simplest solution for your case is using Swing Timer
, which can be used to schedule a regular callback in the EDT where you can do updates
See How to Use Swing Timers for more details
For example...
import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class ScrollingText100 {
public static void main(String[] args) {
new ScrollingText100();
}
public ScrollingText100() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
private String text;
private int index;
private JTextArea textArea;
public TestPane() {
setLayout(new BorderLayout());
textArea = new JTextArea(2, 40);
add(textArea);
text = "Please login to continue...\n" + "Type 'help' for more information.\n";
Timer timer = new Timer(50, new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
if (index < text.length() - 1 && index >= 0) {
String newChar = Character.toString(text.charAt(index));
textArea.append(newChar);
index++;
} else {
textArea.setText(null);
index = 0;
// You could stop the timer here...
}
}
});
timer.start();
}
}
}
Update
If I understand your requirements correctly, something like this ...
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class LoginTerminal {
private JTextArea log = new JTextArea(20, 40);
private JTextField field = new JTextField();
private int index;
private StringBuilder textToDisplay;
private Timer timer;
public static void main(String[] args) {
new LoginTerminal();
}
public LoginTerminal() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
textToDisplay = new StringBuilder(128);
timer = new Timer(50, new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
if (textToDisplay.length() > 0) {
String newChar = Character.toString(textToDisplay.charAt(0));
textToDisplay.delete(0, 1);
log.append(newChar);
} else {
((Timer) e.getSource()).stop();
}
}
});
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(field, BorderLayout.NORTH);
frame.add(new JScrollPane(log));
log.setBackground(Color.BLACK);
log.setForeground(Color.WHITE);
log.setWrapStyleWord(true);
log.setLineWrap(true);
log.setEditable(false);
log.setCaretColor(Color.BLACK);
field.setBackground(Color.BLACK);
field.setForeground(Color.WHITE);
field.setCaretColor(Color.BLACK);
field.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
if (" > HELP".equalsIgnoreCase(field.getText())) {
dumpToLog();
} else {
dumpToLog();
}
}
});
field.setText(" > ");
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public void timerPrint(String text) {
textToDisplay.append(text).append("\n");
if (!timer.isRunning()) {
timer.start();
}
}
public void slowPrint(String str) {
for (int i = 0; i < str.length(); i++) {
log.append("" + str.charAt(i));
try {
Thread.sleep(50);
} catch (InterruptedException e) {
e.printStackTrace();
}
if (i == str.length() - 1) {
log.append("\n");
}
}
}
public void dumpToLog() {
timerPrint(field.getText());
}
}
might be what you are actually looking for.
Note. KeyListener
are not a good choice for JTextComponent
s, in which case it is better to choose ActionListener
.
+1
source to share