Simple line drawing project in swing

Question

hi folks,
i want to write a simple line drawing project. it has a JPanel, a JFrame and JButton.
JPanel and JButton are on JFrame. When Button is clicked,
a line will be added to JPanel but previous lines which have been added are not removed on JPanel.
Could you please help me?

Answer 1

i wrote below codes but it adds first line but when click button �n order to add line, it is not adding line. Please help and thanxs...
import java.awt.BasicStroke;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.Line2D;
import java.util.Enumeration;
import java.util.Vector;
import javax.swing.JButton;
import javax.swing.JComponent;
import javax.swing.WindowConstants;
import javax.swing.SwingUtilities;
public class NewJFrame extends javax.swing.JFrame implements ActionListener {
     private JButton addButton;
     MainPanel mainPane ;
     public Vector lines ;
     * Auto-generated main method to display this JFrame
     public static void main(String[] args) {
          SwingUtilities.invokeLater(new Runnable() {
               public void run() {
                    NewJFrame inst = new NewJFrame();
                    inst.getContentPane().add(new MainPanel(inst.lines));
                    inst.setLocationRelativeTo(null);
                    inst.setVisible(true);
     public NewJFrame() {
          super();
          initGUI();
          lines = new Vector();
          lines.add(0, 30);
          addButton.addActionListener(this);
     private void initGUI() {
          try {
               setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
                    addButton = new JButton();
                    getContentPane().add(addButton, BorderLayout.SOUTH);
                    addButton.setText("ADD");
                    addButton.setPreferredSize(new java.awt.Dimension(71, 21));
               pack();
               setSize(400, 300);
          } catch (Exception e) {
               e.printStackTrace();
     @Override
     public void actionPerformed(ActionEvent e) {
          if(e.getSource() == addButton){
               lines.addElement(Integer.parseInt(lines.get(0).toString())+30);
               mainPane.repaint();
class MainPanel extends JComponent {
     Vector tempLines ;
     MainPanel(Vector lines){
          tempLines = lines;
          setBackground(Color.white);
     public void paintComponent(Graphics g) {
          Enumeration enumeration = tempLines.elements();
          while(enumeration.hasMoreElements()) {
               Integer point = Integer.parseInt(enumeration.nextElement().toString());
               Line2D line = new Line2D.Double(30, point, 200, point);
     Graphics2D g2d = (Graphics2D)g;
     g2d.setStroke(new BasicStroke(5));
     g2d.draw(line);
}