Newbie need help on JPanel graphics

[junpogi]

hello gurus,
need your help. i'm so struggling on this program that i have to do. here's my scenario:
1) i have a frame that is divided by two JPanels, the left and right.
2) the right are subdivided by multiple jpanels and contains buttons and text.
when a button is pressed, it creates a text on the right panel.
3) the right works ok.
4) the left is "not" subdivided. it contains a couple of simple straight lines. and a clored background.
5) what i want to do is: to add additional lines to my left panel when a particular button is pressed from the right panel.
6) thats where im stuck. i'm played around with it but it either make my left drawings disappear or it makes a new panel. h

here's part of my code:

//this is in a different file.
public class LeftSide extends JPanel
{
public void paintComponent(Graphics g)
{
super.paintComponent(g);
setBackground(Color.GREEN);
}

public void paint(Graphics g)
{
super.paint(g);
g.drawLine(275, 50, 275, 500);
}
}

//this is also in a separate file.
private void createBodyGUIs()
{
setLayout(new BorderLayout());

biggerPanel.setLayout(new GridLayout(1,2));

add(biggerPanel, BorderLayout.CENTER);

LeftSide drawings = new LeftSide();
biggerPanel.add(drawings);
createRightColumnGUI(); //creates my goodies on the right side
}


thanks in advance!

[Eranga]

Basically you need two panels first. In one of the panel you need two panels again. Do you design in that way?

[Eranga]

See in this example code, how I handle the layouts.

    public PanelTest() {
        this.setLayout(new GridLayout(1, 2));
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setSize(300, 300);
        
        JPanel one = new JPanel();
        one.add(new JButton("One"));
        
        JPanel two = new JPanel(new GridLayout(2, 1));
        two.add(new JButton("Two"));
        two.add(new JButton("Three"));
        
        this.add(one);
        this.add(two);
    }
    
    public static void main(String[] args) {
        new PanelTest().setVisible(true);
    }

[junpogi]

hello eranga,
thank you for replying. basically, what i have is a frame with panel. that panel is divided in two, the left and the right. i have buttons on the right panel and they work perfectly. my problem is my left panel. i have a straight line drawn on it as you can see from my code. i would like to add another line to it everytime a particular button (from the right panel) is pressed.

i don't know how to do that. i don't know how to add another straight line (grapihcs) on the existing straight line on my left panel. could you help me please?

thank you!

[Fubarable]

Your doing some basic no-no's in your graphics code such as subclassing paint and paintComponent where only paintComponent is needed, calling setBackground from within a paint/paintComponent method,...

I think that you would benefit greatly by reading the Sun graphics tutorials. Good luck.

[hardwired]

The basic idea is to keep the lines in a collection which is a member variable (in class scope) and draw all of the lines on each trip through the paintComponent method.
Another approach is to use a BufferedImage that is the same size as the component. You draw each new line to the image in/via your event code and then simply draw/render the image in the paintComponent method.

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.Line2D;
import java.util.*;
import java.util.List;
import javax.swing.*;

public class AddingLines extends JPanel {
    List<Line2D.Double> lines = new ArrayList<Line2D.Double>();
    Random seed = new Random();

    public AddingLines() {
        setBackground(Color.white);
    }

    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                            RenderingHints.VALUE_ANTIALIAS_ON);
        g2.setPaint(Color.blue);
        for(int i = 0; i < lines.size(); i++) {
            g2.draw(lines.get(i));
        }
    }

    private void addLine() {
        int w = getWidth();
        int h = getHeight();
        int x1 = seed.nextInt(w);
        int y1 = seed.nextInt(h);
        int x2 = seed.nextInt(w);
        int y2 = seed.nextInt(h);
        lines.add(new Line2D.Double(x1, y1, x2, y2));
        repaint();
    }

    private JPanel getLast() {
        JButton button = new JButton("add line");
        button.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                addLine();
            }
        });
        JPanel panel = new JPanel();
        panel.add(button);
        return panel;
     }

    public static void main(String[] args) {
        AddingLines test = new AddingLines();
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.add(test);
        f.add(test.getLast(), "Last");
        f.setSize(400,400);
        f.setLocation(200,200);
        f.setVisible(true);
    }
}

[Fubarable]

It's funny. Our apps were a bit similar:

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.Line2D;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import javax.swing.*;

public class ShowLines
{
  private static final int WIDTH = 400;
  private static final Dimension GP_SIZE = new Dimension(WIDTH, WIDTH);
  private static final String ADD_LINE = "Add Random Line";
  private static final String REMOVE_LINE = "Remove Random Line";
  private static final float STROKE = 6f;
  private JPanel mainPanel = new JPanel();
  private List<Line2D> lineList = new ArrayList<Line2D>();
  private JPanel graphicsPanel = new JPanel()
  {
    protected void paintComponent(Graphics g)
    {
      super.paintComponent(g);
      myPaint(g);
    }
  };

  public ShowLines()
  {
    graphicsPanel.setPreferredSize(GP_SIZE);
    graphicsPanel.setBorder(BorderFactory.createLineBorder(Color.blue, 3));
    JPanel buttonPanel = createButtonPanel();
    
    mainPanel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
    mainPanel.setLayout(new BorderLayout(5, 5));
    mainPanel.add(graphicsPanel, BorderLayout.CENTER);
    mainPanel.add(buttonPanel, BorderLayout.EAST);
  }
  
  private void myPaint(Graphics g)
  {
    Graphics2D g2 = (Graphics2D)g;
    RenderingHints rh = new RenderingHints(
        RenderingHints.KEY_ANTIALIASING,
        RenderingHints.VALUE_ANTIALIAS_ON);
    g2.setRenderingHints(rh);
    g2.setColor(Color.red);
    g2.setStroke(new BasicStroke(STROKE));
    for (Line2D line : lineList)
    {
      g2.draw(line);
    }
  }
  
  private JPanel createButtonPanel()
  {
    JButton addLineBtn = new JButton(ADD_LINE);
    JButton removeLineBtn = new JButton(REMOVE_LINE);
    LineListener lineListener = new LineListener();
    addLineBtn.addActionListener(lineListener);
    removeLineBtn.addActionListener(lineListener);
    
    JPanel innerPanel = new JPanel(new GridLayout(0, 1, 0, 10));
    innerPanel.add(addLineBtn);
    innerPanel.add(removeLineBtn);
    
    JPanel bp = new JPanel();
    bp.add(innerPanel);
    return bp;
  }

  public JComponent getComponent()
  {
    return mainPanel;
  }

  private class LineListener implements ActionListener
  {
    private Random random = new Random();
    
    public void actionPerformed(ActionEvent e)
    {
      String actionCommand = e.getActionCommand();
      if (actionCommand.equals(ADD_LINE))
      {
        Line2D line = new Line2D.Double(
            random.nextInt(WIDTH),
            random.nextInt(WIDTH),
            random.nextInt(WIDTH),
            random.nextInt(WIDTH)
            );
        lineList.add(line);
      }
      else if (actionCommand.equals(REMOVE_LINE))
      {
        if (lineList.size() > 0)
        {
          lineList.remove(0);
        }
      }
      graphicsPanel.repaint();
    }
  }
  private static void createAndShowUI()
  {
    JFrame frame = new JFrame("ShowLines");
    frame.getContentPane().add(new ShowLines().getComponent());
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.pack();
    frame.setLocationRelativeTo(null);
    frame.setVisible(true);
  }

  public static void main(String[] args)
  {
    java.awt.EventQueue.invokeLater(new Runnable()
    {
      public void run()
      {
        createAndShowUI();
      }
    });
  }
}

[junpogi]

thanks guys!

by the way, how can i add regular text at the bottom of the last button? say i wanted to type in a few words.

thanks again!