Java KeyListener changes JFrame label value

Question

I have the following code:

package testOpdracht1; import javax.swing.*; import java.awt.*; import java.awt.event.*; import java.util.Date; import java.text.DateFormat; import java.text.SimpleDateFormat; import java.io.InputStream; public class MainMenu extends JFrame implements KeyListener { public MainMenu() { initUI(); } public final void initUI() { JLabel label1 = new JLabel("text1"); add(label1); addKeyListener(this); setTitle("Bla"); setPreferredSize(new Dimension(400,250)); setMinimumSize(getPreferredSize()); setResizable(true); setLocationRelativeTo(null); setDefaultCloseOperation(EXIT_ON_CLOSE); } public void keyPressed(KeyEvent e) { } public void keyReleased(KeyEvent e) { } public void keyTyped(KeyEvent e) { } public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable() { public void run() { MainMenu ex = new MainMenu(); ex.setVisible(true); } }); } } 

I want to change the text in the label when any button is pressed. How can i do this? I know that I can call methods from the JFrame class, since my MainMenu class extends it, but I cannot find a way to refer to the label element to change the value.

Yours faithfully,

Luxo

Answer 1

Modify your code to look like this:

 package testOpdracht1; import javax.swing.*; import java.awt.*; import java.awt.event.*; import java.util.Date; import java.text.DateFormat; import java.text.SimpleDateFormat; import java.io.InputStream; public class MainMenu extends JFrame implements KeyListener { final JLabel label1 = new JLabel("text1"); public MainMenu() { initUI(); } public final void initUI() { add(label1); addKeyListener(this); setTitle("Bla"); setPreferredSize(new Dimension(400,250)); setMinimumSize(getPreferredSize()); setResizable(true); setLocationRelativeTo(null); setDefaultCloseOperation(EXIT_ON_CLOSE); } public void keyPressed(KeyEvent e) { label1.setText("foo"); } public void keyReleased(KeyEvent e) { } public void keyTyped(KeyEvent e) { } public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable() { public void run() { MainMenu ex = new MainMenu(); ex.setVisible(true); } }); } } 

Answer 2

Declare JLabel as a global variable and create an instance like you in initUI (). Now in your ActionListener methods, when you handle the event, you can change the text of your label there.

Answer 3

You must declare your JLabel as a global variable, and then in any of the keyXXX() methods, you can change your text using the setText() method of the setText() class.