I have public class MainFrame extends JFrame implements ActionListener {
and then later on:
public void keyPressed(KeyEvent e) {
if (e.getKeyCode() == e.VK_LEFT) {
int x = ball.getX() + 1;
ball.setX(x);
}
}
however it does not seem to respond when I believe it should.
If I add keylistener instead of actionlister I cannot compile which I can't understand. I'm new to java however i'm used to C#
You need to implement java.awt.event.KeyListener not a ActionListener to listen for key events.
You need to register your listener on the element (frame) you want to listen on by invoking addKeyListener(...).
Example:
public class TestFrame extends JFrame implements KeyListener {
public static void main(String[] args) throws FileNotFoundException {
TestFrame testFrame = new TestFrame();
testFrame.setSize(100, 100);
testFrame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
testFrame.addKeyListener(testFrame);
testFrame.setVisible(true);
}
#Override
public void keyTyped(KeyEvent e) { }
#Override
public void keyPressed(KeyEvent e) {
System.out.println(e);
}
#Override
public void keyReleased(KeyEvent e) { }
}
Related
When a user clicks the red 'X' button of a JFrame, how do I detect whether the JFrame is open or closed? I have a swing timer where the JFrame keeps updating it's label until the user closes down the JFrame.
int delay = 1000; //milliseconds
final Timer timer = new Timer(delay, null);
timer.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent evt) {
tempLabel.setVisible(true);
String tmp = "test";
tempLabel.setText("Temperature : " + tmp);
// timer.stop();
}
});
timer.start();
You have to implement either the WindowStateListener or the WindowListener. If you use the WindowListener it could look like this:
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;
import javax.swing.Timer;
public class Foo implements WindowListener {
private Timer timer;
public static void main(String args[]){
initTimerComponent();
}
private void initTimerComponent() {
int delay = 1000; //milliseconds
timer = new Timer(delay, null);
timer.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent evt) {
tempLabel.setVisible(true);
String tmp = "test";
tempLabel.setText("Temperature : " + tmp);
}
});
timer.start();
}
#Override
public void windowOpened(WindowEvent e) { }
#Override
public void windowClosing(WindowEvent e) {
timer.stop();
}
#Override
public void windowClosed(WindowEvent e) { }
#Override
public void windowIconified(WindowEvent e) { }
#Override
public void windowDeiconified(WindowEvent e) { }
#Override
public void windowActivated(WindowEvent e) { }
#Override
public void windowDeactivated(WindowEvent e) { }
}
You have to implement them all as WindowListener is an interface and the first concrete class implementing an interface is forced to implement all its abstract methods. But you actually need just one method.
Use this method
public void windowClosing(WindowEvent e) {
timer.stop();
}
to stop your timer as soon as the window is closing after the user clicked the red X.
Answer
addWindowListener(new WindowAdapter() {
//for closing
#Override
public void windowClosing(WindowEvent e) {
JOptionPane.showMessageDialog(null, "Closing");
}
//for closed
#Override
public void windowClosed(WindowEvent e) {
}
});
I want to create a class that implement mouseListener interface (this class will override all mouseListener methods) instead of override all the methods in the main class. When I tring to do so I get an error.
This is my code:
import javax.swing.*;
public class Game {
public Game(){
JFrame frame = new JFrame();
frame.setSize(500,500);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.addMouseListener(new MyMouseListener());
}
public static void main(String[] args) {
Game app = new Game();
}
}
MyMouseListener code:
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
public class MyMouseListener implements KeyListener{
#Override
public void keyTyped(KeyEvent e) {
}
#Override
public void keyPressed(KeyEvent e) {
}
#Override
public void keyReleased(KeyEvent e) {
}
}
edit: I understand my problem was that I implement keyListener insteed of mouseListener in the class MyMouseListener so I changed this and MyMouseListener code is now:
public class MyMouseListener extends Game implements MouseListener{
#Override
public void mouseClicked(MouseEvent e) {
}
#Override
public void mousePressed(MouseEvent e) {
}
#Override
public void mouseReleased(MouseEvent e) {
}
#Override
public void mouseEntered(MouseEvent e) {
}
#Override
public void mouseExited(MouseEvent e) {
}
}
The problem you might be having is the frame not showing up, this is because you did not tell it to show the frame, use the following method:
frame.setVisible(true);
In addition as stated by Jorn Vernee, in your class MyMouseListener you have to implement the MouseListener interface instead of the KeyListener.
I tried this code out and it worked just fine:
import javax.swing.JFrame;
public class Game {
public Game(){
JFrame frame = new JFrame();
frame.setSize(500,500);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.addMouseListener(new MyMouseListener());
frame.setVisible(true);
}
public static void main(String[] args) {
Game app = new Game();
}
}
Code for MyMouseListener:
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
public class MyMouseListener implements MouseListener{
#Override
public void mouseClicked(MouseEvent e) {
// TODO Auto-generated method stub
System.out.println("clicked");
}
#Override
public void mousePressed(MouseEvent e) {
// TODO Auto-generated method stub
}
#Override
public void mouseReleased(MouseEvent e) {
// TODO Auto-generated method stub
}
#Override
public void mouseEntered(MouseEvent e) {
// TODO Auto-generated method stub
}
#Override
public void mouseExited(MouseEvent e) {
// TODO Auto-generated method stub
}
}
This question already has an answer here:
Pong Paddle bottom doesn't move up when UP key is pressed
(1 answer)
Closed 7 years ago.
So I have seen a couple of these questions asked. They all say that you should not be using a Keylistener but instead a KeyBinding thing. But when I go to use the Keybinding it does not work. I understand I probably should be using the KeyBinding thing but is there a way that I can fix my code so that the KeyListener works. Thank you.
Game Class:
public class Game extends JFrame implements KeyListener{
public static int ppx,ppy;
public static void main(String[] args) {
JFrame frame = new JFrame("Game");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(500,600);
frame.add(new THIng());
frame.setVisible(true);
}
#Override
public void keyTyped(KeyEvent e) {
}
#Override
public void keyPressed(KeyEvent e) {
int keycode = e.getKeyCode();
if(keycode == KeyEvent.VK_D){
System.out.println("Debug");
}
}
#Override
public void keyReleased(KeyEvent e) {
}
}
THIng Class:
public class THIng extends JPanel{
public static int px,py,pwid,phei;
public void main(String[]args){
Timer timer;
timer = new Timer(60,
new ActionListener(){
public void actionPerformed(ActionEvent evt){
p();
}
}
);
}
public THIng(){
px = Game.ppx;py = Game.ppy;pwid = 50;phei = pwid;
}
#Override
public Dimension getPreferredSize(){
return new Dimension(500,600);
}
#Override
public void paintComponent(Graphics g){
super.paintComponent(g);
Graphics p = (Graphics)g;
p.drawRect(px,py,pwid,phei);
}
public void p(){
repaint();
}
}
you don't have to make a constructor, just add frame.addKeyListener(this); where you have set other properties of the JFrame.
as MadProgrammer has pointed out the right thing to do is use the Key Bindings API which you can see step by step Key Bindings API
add a constructor that adds a key listener and in your main make it class Game instead of JFrame
public class Game extends JFrame implements KeyListener{
public static int ppx,ppy;
public Game(String string) {
addKeyListener(this);
// TODO Auto-generated constructor stub
}
public static void main(String[] args) {
Game frame = new Game("Game");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(500,600);
frame.add(new THIng());
frame.setVisible(true);
}
#Override
public void keyTyped(KeyEvent e) {
}
#Override
public void keyPressed(KeyEvent e) {
int keycode = e.getKeyCode();
if(keycode == KeyEvent.VK_D){
System.out.println("Debug");
}
}
#Override
public void keyReleased(KeyEvent arg0) {
// TODO Auto-generated method stub
}
}
I am trying to do something when one of the arrow keys are pressed using the KeyListener in my JPanel class. Here is my code:
public class TestPanel extends JPanel implements KeyListener{
public TestPanel(){
this.addKeyListener(this);
this.setFocusable(true);
this.requestFocusInWindow();
}
public void keyPressed(KeyEvent e) {
if (e.getKeyCode() == KeyEvent.VK_RIGHT) {
System.out.println("Right");
}
if (e.getKeyCode() == KeyEvent.VK_LEFT) {
System.out.println("Left");
}
}
public void keyTyped(KeyEvent e) {}
public void keyReleased(KeyEvent e) {}
}
My main method adds a new instance of this panel to a frame and displays it. Do I need to add the keylistener to the JFrame? In my case, this would be difficult and inefficient, so I would like to make it work with this JPanel if possible. Anyone know what I am doing wrong?
EDIT: Key Bindings code that does not work either:
public class GamePanel extends JPanel implements ActionListener{
//Constructor
public GamePanel(){
setupKeyBinding();
this.setFocusable(true);
this.requestFocusInWindow();
}
private void setupKeyBinding() {
int condition = JComponent.WHEN_IN_FOCUSED_WINDOW;
InputMap inMap = getInputMap(condition);
ActionMap actMap = getActionMap();
inMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, 0), "Left");
actMap.put("Left", new leftAction());
}
private class leftAction extends AbstractAction {
public void actionPerformed(ActionEvent e) {
System.out.println("test");
}
}
public void actionPerformed(ActionEvent e) {
//some other game info
}
}
Can someone tell me why this doesnt work either? (my second action listener is for other stuff needed for my game)
If you search this problem, you'll see that it is asked and has been solved many times.
KeyListeners need to be on the focused component to work. One solution is to give your component the focus after first making it focusable.
Better by a long shot however is to use Key Bindings. Google the tutorial on this.
Please have a look at my answer to this question for more on this, including many of the gory details.
For reference, I've create an example using your approach; while it works, it also suggests a focus problem elsewhere in your code. Key Bindings avoid this, as shown here.
Addendum: Here's my working key binding.
private static class TestPanel extends JPanel {
private static final String LEFT = "Left";
private Action left = new AbstractAction(LEFT) {
#Override
public void actionPerformed(ActionEvent e) {
System.out.println(LEFT);
}
};
private static final String RIGHT = "Right";
private Action right = new AbstractAction(RIGHT) {
#Override
public void actionPerformed(ActionEvent e) {
System.out.println(RIGHT);
}
};
public TestPanel() {
this.getInputMap().put(
KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, 0), LEFT);
this.getActionMap().put(LEFT, left);
this.getInputMap().put(
KeyStroke.getKeyStroke(KeyEvent.VK_RIGHT, 0), RIGHT);
this.getActionMap().put(RIGHT, right);
}
}
Original SSCCE:
import java.awt.EventQueue;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.JFrame;
import javax.swing.JPanel;
/**
* #see https://stackoverflow.com/a/16531380/230513
*/
public class Test {
private void display() {
JFrame f = new JFrame("Test");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.add(new TestPanel());
f.pack();
f.setLocationRelativeTo(null);
f.setVisible(true);
}
private static class TestPanel extends JPanel implements KeyListener {
public TestPanel() {
this.addKeyListener(this);
this.setFocusable(true);
this.requestFocusInWindow();
}
#Override
public void keyPressed(KeyEvent e) {
if (e.getKeyCode() == KeyEvent.VK_RIGHT) {
System.out.println("Right");
}
if (e.getKeyCode() == KeyEvent.VK_LEFT) {
System.out.println("Left");
}
}
#Override
public void keyTyped(KeyEvent e) {
}
#Override
public void keyReleased(KeyEvent e) {
}
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
new Test().display();
}
});
}
}
For receives key events on JPanel you must set focus:
setFocusable(true);
requestFocus();
the JPanel now has focus, so it receives key events
I had to do two things: I added comp.setFocusable(true); to the component comp that listens to key events, and I added comp.requestFocus(); to each action which caused comp to lose the focus.
I am trying to do something when one of the arrow keys are pressed using the KeyListener in my JPanel class. Here is my code:
public class TestPanel extends JPanel implements KeyListener{
public TestPanel(){
this.addKeyListener(this);
this.setFocusable(true);
this.requestFocusInWindow();
}
public void keyPressed(KeyEvent e) {
if (e.getKeyCode() == KeyEvent.VK_RIGHT) {
System.out.println("Right");
}
if (e.getKeyCode() == KeyEvent.VK_LEFT) {
System.out.println("Left");
}
}
public void keyTyped(KeyEvent e) {}
public void keyReleased(KeyEvent e) {}
}
My main method adds a new instance of this panel to a frame and displays it. Do I need to add the keylistener to the JFrame? In my case, this would be difficult and inefficient, so I would like to make it work with this JPanel if possible. Anyone know what I am doing wrong?
EDIT: Key Bindings code that does not work either:
public class GamePanel extends JPanel implements ActionListener{
//Constructor
public GamePanel(){
setupKeyBinding();
this.setFocusable(true);
this.requestFocusInWindow();
}
private void setupKeyBinding() {
int condition = JComponent.WHEN_IN_FOCUSED_WINDOW;
InputMap inMap = getInputMap(condition);
ActionMap actMap = getActionMap();
inMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, 0), "Left");
actMap.put("Left", new leftAction());
}
private class leftAction extends AbstractAction {
public void actionPerformed(ActionEvent e) {
System.out.println("test");
}
}
public void actionPerformed(ActionEvent e) {
//some other game info
}
}
Can someone tell me why this doesnt work either? (my second action listener is for other stuff needed for my game)
If you search this problem, you'll see that it is asked and has been solved many times.
KeyListeners need to be on the focused component to work. One solution is to give your component the focus after first making it focusable.
Better by a long shot however is to use Key Bindings. Google the tutorial on this.
Please have a look at my answer to this question for more on this, including many of the gory details.
For reference, I've create an example using your approach; while it works, it also suggests a focus problem elsewhere in your code. Key Bindings avoid this, as shown here.
Addendum: Here's my working key binding.
private static class TestPanel extends JPanel {
private static final String LEFT = "Left";
private Action left = new AbstractAction(LEFT) {
#Override
public void actionPerformed(ActionEvent e) {
System.out.println(LEFT);
}
};
private static final String RIGHT = "Right";
private Action right = new AbstractAction(RIGHT) {
#Override
public void actionPerformed(ActionEvent e) {
System.out.println(RIGHT);
}
};
public TestPanel() {
this.getInputMap().put(
KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, 0), LEFT);
this.getActionMap().put(LEFT, left);
this.getInputMap().put(
KeyStroke.getKeyStroke(KeyEvent.VK_RIGHT, 0), RIGHT);
this.getActionMap().put(RIGHT, right);
}
}
Original SSCCE:
import java.awt.EventQueue;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.JFrame;
import javax.swing.JPanel;
/**
* #see https://stackoverflow.com/a/16531380/230513
*/
public class Test {
private void display() {
JFrame f = new JFrame("Test");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.add(new TestPanel());
f.pack();
f.setLocationRelativeTo(null);
f.setVisible(true);
}
private static class TestPanel extends JPanel implements KeyListener {
public TestPanel() {
this.addKeyListener(this);
this.setFocusable(true);
this.requestFocusInWindow();
}
#Override
public void keyPressed(KeyEvent e) {
if (e.getKeyCode() == KeyEvent.VK_RIGHT) {
System.out.println("Right");
}
if (e.getKeyCode() == KeyEvent.VK_LEFT) {
System.out.println("Left");
}
}
#Override
public void keyTyped(KeyEvent e) {
}
#Override
public void keyReleased(KeyEvent e) {
}
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
new Test().display();
}
});
}
}
For receives key events on JPanel you must set focus:
setFocusable(true);
requestFocus();
the JPanel now has focus, so it receives key events
I had to do two things: I added comp.setFocusable(true); to the component comp that listens to key events, and I added comp.requestFocus(); to each action which caused comp to lose the focus.