How do I make the buttons on this GUI work?

[Alioune]

I'm trying to make a GUI that will increase a number when you click one button and decrease that number when you click another button. This is my code:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;


public class PushCounter
{
   static JTextField textArea;
   static int count = 0;
 
   public static void main(String[] args)
   {
     
       JFrame frame = new JFrame("PushCounter");
       frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
       JPanel panel = new JPanel();
       JButton upButton = new JButton("Up");
       JButton downButton = new JButton("Down");
       JTextField textArea = new JTextField(15);
       JLabel label = new JLabel("Count");
     
     
       upButton.addActionListener(new upButtonListener());
       downButton.addActionListener(new downButtonListener());
     
       panel.add(label);
       panel.add(textArea);
       panel.add(downButton);
       panel.add(upButton);
     
     
       frame.getContentPane().add(panel);
       frame.setVisible(true);
       frame.pack();
     
   }
 
   private static class upButtonListener implements ActionListener
   {
     
       public void actionPerformed(ActionEvent event)
       {
           ++count;
           textArea.setText(Integer.toString(count));
       }
   }
 
   private static class downButtonListener implements ActionListener
   {
     
       public void actionPerformed(ActionEvent event)
       {
           --count;
           textArea.setText(Integer.toString(count));
       }
   }
 
}

It compiles, but the GUI itself doesn't work. What's wrong with it? How would you create something like this and why?

 

[John Joe]

What did you mean by GUI itself doesn't work ? Can you specific the error?

 

[Alioune]

What did you mean by GUI itself doesn't work ? Can you specific the error?

If you run the code, you'll find that a GUI appears. If you click either of the buttons the program crashes. I have no idea why.

 

[John Joe]

Modify your code to this

public class PushCounter {

    static JTextField textArea;
    static int count = 0;

    public static void main(String[] args) {

        JFrame frame = new JFrame("PushCounter");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JPanel panel = new JPanel();
        JButton upButton = new JButton("Up");
        JButton downButton = new JButton("Down");
        textArea = new JTextField(15);  // use one object enough
        JLabel label = new JLabel("Count");

        ActionListener showComponentAction = new upButtonListener(upButton);
        upButton.addActionListener(showComponentAction);

        ActionListener showComponentAction1 = new downButtonListener(downButton);
        downButton.addActionListener(showComponentAction1);

        panel.add(label);
        panel.add(textArea);
        panel.add(downButton);
        panel.add(upButton);

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

    }

    private static class upButtonListener implements ActionListener {

        private JButton btn;

        public upButtonListener(JButton btn) {
            this.btn = btn;
        }

        public void actionPerformed(ActionEvent event) {
            ++count;
            System.out.println(count);
            textArea.setText(Integer.toString(count));
        }
    }

    private static class downButtonListener implements ActionListener {

        private JButton downBtn;

        public downButtonListener(JButton downBtn) {
            this.downBtn = downBtn;
        }

        public void actionPerformed(ActionEvent event) {
            --count;
            textArea.setText(Integer.toString(count));
        }
    }

}

I also noticed that you are creating two JTextField objects. Create one had enough.

Refer to this https://stackoverflow.com/a/26166672/5156075 to get clear explanation.

 

[Alioune]

Thanks, that solved the problem. How would you make a project like this? Other than what you said, is there anything about the structure that could be done better or does it not matter?

 

[John Joe]

Thanks, that solved the problem. How would you make a project like this? Other than what you said, is there anything about the structure that could be done better or does it not matter?

Why would you need to create two static class for upButtonListener and downButtonListener ? For me I will do everything just in one class.

 

[Alioune]

I thought I had to create a private class containing the actionPerformed class. I guess I could have done it in the same class. I'm a novice at this language.

 

[Alioune]

How do I make it so that it continues to perform the action when I click and hold the button?

 

[John Joe]

How do I make it so that it continues to perform the action when I click and hold the button?

For me I will write like this. Use ActionListener for the two buttons.

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class PushCounter extends JPanel {

    JTextField textArea;
    int count = 0;

    public PushCounter() {
        JPanel panel = new JPanel();
        JButton upButton = new JButton("Up");
        JButton downButton = new JButton("Down");
        textArea = new JTextField(15); // use one object enough
        JLabel label = new JLabel("Count");

        upButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                ++count;
                textArea.setText(Integer.toString(count));
            }
        });

        downButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                --count;
                textArea.setText(Integer.toString(count));
            }
        });

        panel.add(label);
        panel.add(textArea);
        panel.add(downButton);
        panel.add(upButton);
        add(panel);
    }

    public static void main(String[] args) {
        PushCounter pc = new PushCounter();
        JFrame frame = new JFrame("PushCounter");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(pc);
        frame.setVisible(true);
        frame.pack();
    }
}

 

[Alioune]

There are problems with the following lines:

add(panel);
frame.add(pc);

I'm using the Eclipse ide. It says "method add(JPanel) is undefined for the type PushCounter" and "the method add(Component) in the type Container is not applicable for the arguments (PushCounter)".

 

[John Joe]

It works fine in my PC