I'm having a problem with JButton. I need to change the text on the goPauseButton when it has been clicked, but I get this error: goPauseButton cannot be resolved
. I'm quite new to Java, so I started trying to solve the issue using techniques from other languages such as Free Pascal. There you need to refer to the class where the button is in, and then the button. In my code it would look like this:
PrisonersDilemma.goPauseButton.setText("Pause");
But then I get this error: Cannot make a static reference to the non-static field PrisonersDilemma.goPauseButton
This is my code (so far), I've erased unimportant things:
Main class
import java.awt.BorderLayout;
import java.awt.GridLayout;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JSlider;
import javax.swing.SwingUtilities;
import javax.swing.JButton;
import javax.swing.JLabel;
import java.util.Hashtable;
//...
public class PrisonersDilemma /* possible extends... */ {
// declaring
JFrame frame;
PlayingField field;
JPanel componentPanel;
public JButton goPauseButton;
public JPanel createComponentPanel() {
componentPanel = new JPanel();
componentPanel.setLayout(new GridLayout(2,6));
// set goPauseButton
goPauseButton = new JButton("GO!");
goPauseButton.addActionListener(field);
goPauseButton.setBounds(110,350, 80,20); // first coordinates, then size
frame.add(goPauseButton);
return componentPanel;
}
void buildGUI() {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
field = new PlayingField();
// set frame
frame = new JFrame("Prisoners Dilemma");
frame.add(field);
createComponentPanel();
frame.add(field, BorderLayout.CENTER);
frame.setLocation(200, 200);
frame.pack();
frame.setVisible(true);
frame.setSize(400, 450);
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
} );
}
Class with ActionEventHandler
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.JButton;
public class PlayingField extends JPanel
implements ActionListener,
ChangeListener {
private boolean started;
@Override
public void actionPerformed(ActionEvent e) {
// TODO
if ("GO!".equals(e.getActionCommand())){
System.out.println("GO!");
started = true;
goPauseButton.setText("Pause"); // here is the error
} else if ("Pause".equals(e.getActionCommand())){
System.out.println("Pause");
started = false;
} else if ("Reset".equals(e.getActionCommand())){
System.out.println("Reset");
}
}
}
CodePudding user response:
I think you need to change the way you're approaching the problem. The PlayingField
has no responsibility for modifying the state of the goPauseButton
in PrisonersDilemma
. Instead, PrisonersDilemma
should update the goPauseButton
and call an appropriate method of PlayingField
For example...
goPauseButton.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
goPauseButton.setText("Pause");
field.start();
}
});
And...
public class PlayingField extends JPanel {
public void start() {
System.out.println("GO!");
started = true;
}
public void pause() {
started = false;
System.out.println("Pause");
}
public void reset() {
System.out.println("Reset");
}
}