Java Graphics - draw rectangle

Question

I am trying to make a program that paints 16 rectangles in a windows . When you click on a rectangle with the mouse, it should disappear. The instructions tell me to create a class named Rektangel with the variables x, y, b, h (length and width in Swedish). Then I should create 16 objects of the type Rectangel and store them in a list.

I made three classes, named Panel14_1, Frame14_1 and Rektangel. I tried to pull the Panel into the frame but it doesn't work. When I run the program, it only opens a window and there are no red rectangles in it ...

Frame

package ovning14__1;
public class Frame14__1 extends javax.swing.JFrame {
 /**
 * Creates new form Frame14__1
 */
 public Frame14__1() {
 initComponents();
 }
 /**
 * This method is called from within the constructor to initialize the form.
 * WARNING: Do NOT modify this code. The content of this method is always
 * regenerated by the Form Editor.
 */
 @SuppressWarnings("unchecked")
 // <editor-fold defaultstate="collapsed" desc="Generated Code"> 
 private void initComponents() {
 setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
 javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
 getContentPane().setLayout(layout);
 layout.setHorizontalGroup(
 layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
 .addGap(0, 400, Short.MAX_VALUE)
 );
 layout.setVerticalGroup(
 layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
 .addGap(0, 300, Short.MAX_VALUE)
 );
 pack();
 }// </editor-fold> 
 /**
 * @param args the command line arguments
 */
 public static void main(String args[]) {
 /* Set the Nimbus look and feel */
 //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
 /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
 * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
 */
 try {
 for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
 if ("Nimbus".equals(info.getName())) {
 javax.swing.UIManager.setLookAndFeel(info.getClassName());
 break;
 }
 }
 } catch (ClassNotFoundException ex) {
 java.util.logging.Logger.getLogger(Frame14__1.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
 } catch (InstantiationException ex) {
 java.util.logging.Logger.getLogger(Frame14__1.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
 } catch (IllegalAccessException ex) {
 java.util.logging.Logger.getLogger(Frame14__1.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
 } catch (javax.swing.UnsupportedLookAndFeelException ex) {
 java.util.logging.Logger.getLogger(Frame14__1.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
 }
 //</editor-fold>
 /* Create and display the form */
 java.awt.EventQueue.invokeLater(() -> {
 new Frame14__1().setVisible(true);
 });
 }
 // Variables declaration - do not modify 
 // End of variables declaration 
}

Rektangel

package ovning14__1;
import java.awt.Color;
import java.awt.Graphics;
public class Rektangel {
 private int x = 0;
 private int y = 0;
 private int b = 10;
 private int h = 10;
 public Rektangel(int x, int y, int h, int b) {
 this.x = x;
 this.y = y;
 this.b = b;
 this.h = h;
 }
 public void Rita(Graphics g){
 g.setColor(Color.RED);
 g.fillRect(x, y, b, h);
 }
 public boolean ärTräffad(int musX, int musY){
 boolean träffad = false;
 if (musX > x && musX < (x+h) && musY > y && musY < (y+b)) {
 träffad = true;
 }
 return träffad;
 }
}

Panel

package ovning14__1;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.util.ArrayList;
public class Panel14_1 extends javax.swing.JPanel {
 private final ArrayList<Rektangel> rektanglar = new ArrayList<>();
 private boolean speletÄrSlut = false;
 public Panel14_1() {
 initComponents();
 for (int rad = 0; rad < 4; rad++){
 for (int kolumn = 0; kolumn < 6; kolumn++){
 int x = 10 + 50 * kolumn;
 int y = 10 + 30 * rad;
 int h = 30;
 int b = 20;
 Rektangel rektangel = new Rektangel(x, y, h, b);
 rektanglar.add(rektangel);
 }
 }
 }
 @Override
 protected void printComponent(Graphics g) {
 super.printComponent(g);
 for (int i = 0; i < rektanglar.size(); i++){
 Rektangel rektangel = rektanglar.get(i);
 rektangel.Rita(g);
 }
 if (speletÄrSlut) {
 String text = "Grattis";
 Font font = new Font (Font.SANS_SERIF, Font.PLAIN, 30);
 g.setFont(font);
 g.setColor(Color.BLUE);
 int x = 25;
 int y = 30;
 g.drawString(text, x, y);
 }
 }
 @SuppressWarnings("unchecked")
 // <editor-fold defaultstate="collapsed" desc="Generated Code"> 
 private void initComponents() {
 addMouseListener(new java.awt.event.MouseAdapter() {
 public void mousePressed(java.awt.event.MouseEvent evt) {
 formMousePressed(evt);
 }
 });
 javax.swing.GroupLayout layout = new javax.swing.GroupLayout(this);
 this.setLayout(layout);
 layout.setHorizontalGroup(
 layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
 .addGap(0, 400, Short.MAX_VALUE)
 );
 layout.setVerticalGroup(
 layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
 .addGap(0, 300, Short.MAX_VALUE)
 );
 }// </editor-fold> 
 private void formMousePressed(java.awt.event.MouseEvent evt) { 
 boolean träff = false;
 for (int i =0; i < rektanglar.size() && !träff; i++){
 Rektangel rektangel = rektanglar.get(i);
 if (rektangel.ärTräffad(evt.getX(), evt.getY())){
 rektanglar.remove(i);
 träff= true;
 }
 }
 if(rektanglar.isEmpty()){
 speletÄrSlut = true;
 }
 repaint();
 } 
}
// Variables declaration - do not modify 
// End of variables declaration 

• Bashir: where are the images?

Answer 1

Hello and welcome to stackoverflow!! :D

To paint a rectangle use Graphics.fillRect(x,y,w,h) or for just the outline use Graphics.drawRect(x,y,w,h.

If you want them to disappear, then you have to paint your JFrame if you click on a rectangle with the mouse. I would create a JButton and add an ActionListener.

Edit: Overwrite the paintComponent method and not printComponent

Answer 2

The first thing you need to do is to add the JPanel to the JFrame by: add(new Panel14_1()). There is no need to set a GroupLayout to the JFrame. The default (BorderLayout) will do the job. So

public class Frame14__1 extends javax.swing.JFrame {
 public Frame14__1() {
 initComponents();
 }
 private void initComponents() {
 setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
 add(new Panel14_1()); //add a panel to frame
 pack();
 }
 public static void main(String args[]) {
 ..no change is needed 
 }
} 

After implementing those changes you'll see the rectangles.
In Panel14_1 although overriding printComponent should work you should override paintComponent:

protected void paintComponent(Graphics g) { //not printComponent
 super.paintComponent(g);
 ..no change in the following code 
}

---

Side note: according to Java Naming conventions Rita(Graphics g) should be rita(Graphics g)