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I have a problem with a seemingly simple program. It is a ball that moves across the screen. However I don't know for what reason when I add to JPanel it doesn't work, the problem is created by: initComponents (); However, I need that method.

Does anyone have a solution?

Main class JFrame with JPanel:

I deleted all the parts created by Netbeans, in order to provide visibility, while of course they remain in the original code.

 package newpackage;

public class NewJFrame extends javax.swing.JFrame {

    public NewJFrame() {
        initComponents();
        jPanel1.add(new Core());
        
    }
  public static void main(String args[]) {
        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new NewJFrame().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JPanel jPanel1;
    // End of variables declaration                   
}

Circle JComponent class:

    package newpackage;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.Timer;
import javax.swing.JComponent;

public class Circle extends JComponent {

    int x, y, bounds = 80;
    boolean move_up, move_left;
    public Circle() {

        Timer timer = new Timer(10, new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {

                if (x > getWidth() - bounds) {
                    move_left = true;
                }
                if (x < 0) {
                    move_left = false;
                }
                if (move_left) {
                    x -= 1;
                } else {
                    x += 1;
                }
                if (y > getHeight() - bounds) {
                    move_up = true;
                }
                if (y < 0) {
                    move_up = false;
                }
                if (move_up) {
                    y -= 1;
                } else {
                    y += 1;
                }
                repaint();
            }
        });
        timer.start();
    }

    public void paintComponent(Graphics g) {
        Graphics2D g2d = (Graphics2D) g;
        super.paintComponent(g2d);
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        g2d.setColor(Color.RED);
        g2d.fillOval(x, y, bounds, bounds);
    }
}
vojvoda ljubinko
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    Probably the problem is that you are doing custom painting and you don't override the `getPreferredSize()` method of the panel so there is nothing to paint. Read the Swing tutorial on [Custom Painting](https://docs.oracle.com/javase/tutorial/uiswing/painting/index.html) for more information and working examples. You can also check out https://stackoverflow.com/questions/54028090/get-width-and-height-of-jpanel-outside-of-the-class/54028681#54028681 for a complete example that animates multiple balls. – camickr Mar 15 '22 at 17:08

0 Answers0