Painting graphics on JPanel

Question

hi all,
below is my code,
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.Graphics2D;
import java.awt.Graphics.*;
public class Testing extends JFrame implements ActionListener
String x[] = { " ", "Material A", "Material B", "Material C"};
String y[] = { "                       ", "+5", "+4", "+3", "+2", "+1", " 0",
     "-1", "-2", "-3", "-2", "-5" };
private JButton Plot, End;
private Container c;
private JPanel centerPanel, northPanel, southPanel;
private JComboBox designMaterialx, materialRatingy;
String desMaterial = "";
public Testing()
super( "Welcome" );
     Container c = getContentPane();
     centerPanel = new JPanel()
          protected void paintComponent(Graphics g)
          super.paintComponent(g);
          Graphics2D g2d = (Graphics2D)g;
          g.setColor(Color.blue);
g.drawRect(120, 120, 20, 200);
g.drawString ("Material", 30, 220);
g.drawString ("Ratings", 30, 240);
g.drawString ("+5", 102, 130);
g.drawString ("0", 107, 220);
g.drawString ("-5", 102, 315);
          g.setColor(Color.red);
          g.drawRect(120, 321, 20, 200);
          g.drawString ("Design", 30, 410);
          g.drawString ("Materials", 30, 430);
          g2d.rotate(-Math.PI/2.0,250.0,250.0);
          g.setColor(Color.black);
          g.drawString(desMaterial, -15, 135);
          centerPanel.setBackground(Color.white);
     c.add( centerPanel, BorderLayout.CENTER);
     setVisible(true);
          northPanel = new JPanel();
          northPanel.add(new Label( "Please choose accordingly:" ));
     northPanel.setLayout (new FlowLayout(FlowLayout.CENTER, 20, 0));
designMaterialx = new JComboBox( x );
designMaterialx.setMaximumRowCount( 2 );
designMaterialx.setBorder(BorderFactory.createTitledBorder("Design Materials"));
northPanel.add( designMaterialx );
designMaterialx.setEditable(true);
materialRatingy = new JComboBox( y );
materialRatingy.setMaximumRowCount( 2 );
materialRatingy.setBorder(BorderFactory.createTitledBorder("Material Ratings"));
northPanel.add( materialRatingy );
c.add( northPanel, BorderLayout.NORTH );
setVisible( true );
southPanel = new JPanel();
Plot = new JButton( "Plot" );
End = new JButton( "End" );
southPanel.add( Plot );
southPanel.add( End );
c.add( southPanel, BorderLayout.SOUTH );
setVisible( true );
Plot.addActionListener(this);
End.addActionListener(this);
Plot.addActionListener(new ActionListener()
public void actionPerformed(ActionEvent e)
desMaterial = designMaterialx.getSelectedItem().toString();
centerPanel.repaint();
System.out.println(desMaterial);
pack();
public static void main( String args[] )
Testing app = new Testing();
app.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
public void actionPerformed(ActionEvent e)
     if(e.getSource()==Plot)
          System.out.println("Plot");
     else if(e.getSource()==End)
          System.exit(0);
at the moment when the plot jButton is pressed, the selected values of the design materials jComboBox will be painted on the centerPanel inside the red rectangle. upon subsequent selection of the design materials & pressing of the plot jbutton, i wish to add them next to the existing ones but i'm not sure how to do this. could anyone out there help me on this? any kind of help would be appreciated.
thanks in advance.
rolf

Answer 1

Here's a bunch of ideasimport java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.ArrayList;
public class Test3 extends JFrame {
  MyGraph mg = new MyGraph();
  JTextField nameField = new JTextField("Sample2");
  JTextField valueField = new JTextField("100");
  public Test3() {
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    Container content = getContentPane();
    mg.addData(new MyData("Sample",50));
    content.add(mg, BorderLayout.CENTER);
    JPanel dataPanel = new JPanel();
    dataPanel.add(new JLabel("Name:"));
    dataPanel.add(nameField);
    dataPanel.add(new JLabel("Value:"));
    dataPanel.add(valueField);
    JButton jb = new JButton("Add");
    dataPanel.add(jb);
    jb.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent ae) {
        mg.addData(new MyData(nameField.getText(),Integer.parseInt(valueField.getText())));
        mg.repaint();
    content.add(dataPanel, BorderLayout.NORTH);
    setSize(300,300);
  public static void main(String[] args) { new Test3().setVisible(true); }
class MyGraph extends JPanel {
  ArrayList al = new ArrayList();
  public void addData(MyData data) { al.add(data); }
  public void paintComponent(Graphics g) {
    Graphics2D g2d = (Graphics2D)g;
    super.paintComponent(g2d);
    g2d.setColor(Color.red);
    int height = getHeight(), width=getWidth();
    for (int i=0; i<al.size(); i++) {
      MyData md = (MyData)al.get(i);
      g2d.drawRect(i*20,height-md.getNum(),17,md.getNum());
    g2d.rotate(-Math.PI/2.0,width/2,height/2);
    g2d.setColor(Color.blue);
    for (int i=0; i<al.size(); i++) {
      MyData md = (MyData)al.get(i);
      g2d.drawString(md.getName(),30,i*20-15);
class MyData {
  String name;
  int num;
  public MyData(String name, int num) {
    this.name=name;
    this.num=num;
  public String getName() { return name; }
  public int getNum() { return num; }
}