How To:Use a JSlider to adjust Text size in a JPanel

[louiebagz]

hi guys,

need some help on this.

im working on a program that uses a JSlider... Some texts are rendered on a JPanel... I want to give a zooming in/out effect by using the JSlider to change the size of the text...

I have provided the link for the expected interaction.
http://www.geocities.com/louiebagz/files/jslider.jpg

Below is the code I have...

maybe you can help... thanks!

Code:

/*
 * TextSlider.java
 *
 * Created on June 28, 2007, 7:28 PM
 *
 * To change this template, choose Tools | Template Manager
 * and open the template in the editor.
 */

import java.awt.*;
import java.awt.font.*;
import java.awt.geom.Rectangle2D;
import javax.swing.*;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JSlider;
import javax.swing.SwingConstants;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

/**
 *
 * @author louiebagz
 */
public class TextSlider extends JFrame{
    private TextSpace ssfp; 
    private JSlider zoomSlider;
    private JScrollPane scrollPane;

  public TextSlider() {
    super("Text Processing Demo");

    Container container = getContentPane();
    container.setLayout(new BorderLayout(5, 5));

    ssfp = new TextSpace();
    scrollPane = new JScrollPane(ssfp);
    
    //container.add(new JScrollPane(imagePanel), BorderLayout.CENTER);
    container.add(scrollPane, BorderLayout.CENTER);
               
    zoomSlider = new JSlider(SwingConstants.VERTICAL, 1, 10, 1);
    zoomSlider.setMajorTickSpacing(1);
    zoomSlider.setPaintTicks(true);
    zoomSlider.addChangeListener(new ChangeListener() {
      public void stateChanged(ChangeEvent e) {
        ssfp.revalidate();
        repaint();
      }
    });
    container.add(zoomSlider, BorderLayout.EAST);

    pack();
    setVisible(true);
  }
  
    private class TextSpace extends JPanel {
        String[] lines = {
                "Hello World",
                "How are you today?",
                "More text here",
                "Fine...",
                "And you???"
        };

        Dimension size = new Dimension(400,240);
        float x1 = 0;
        boolean firstTime = true;

        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2 = (Graphics2D)g;
            g2.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING,
                                RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
            int x0 = 60;
            int y0 = 40;
            Font font = g2.getFont().deriveFont(20f);
            g2.setFont(font);
            FontRenderContext frc = g2.getFontRenderContext();
            if(firstTime)
                x1 = determineSize(font, frc, x0, y0);
            float y = y0;
            for(int j = 0; j < lines.length; j++) {
                String s = lines[j];
                float width = (float)font.getStringBounds(s, frc).getWidth();
                LineMetrics lm = font.getLineMetrics(s, frc);
                float height = lm.getAscent() + lm.getDescent();
                float sx = x0;
                float sy = y + lm.getAscent();
                g2.setPaint(Color.black);
                g2.drawString(s, sx, sy);
                //g2.setPaint(Color.green);
                x1 = (x0+width+25 > x1) ? x0+width+25 : x1;
                //g2.fill(new Rectangle2D.Float(x1, y, width, height));
                y +=height;
            }
        }

        private float determineSize(Font font, FontRenderContext frc, int x0, int y0) {
            Dimension d = new Dimension();
            float y = y0;
            float x = 0;
            for(int j = 0; j < lines.length; j++) {
                String s = lines[j];
                float width = (float)font.getStringBounds(s, frc).getWidth();
                LineMetrics lm = font.getLineMetrics(s, frc);
                float height = lm.getAscent() + lm.getDescent();
                if((2*x0+width) > x)
                    x = 2*x0+width;
                y +=height;
                if(x+width+x0 > d.width)
                    d.width = (int)(x+width+x0);
                if(y+y0> d.height)
                    d.height = (int)(y+y0);
            }
            size.width = Math.max(d.width, size.width);
            size.height = Math.max(d.height, size.height);
            revalidate();
            firstTime = false;
            return x;
        }

        public Dimension getPreferredSize() {
            return size;
        }
    }
  
    public static void main(String args[]) {
        TextSlider app = new TextSlider();
        app.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}

[JavaBean]

You are not changing the size of the text from your JSlider. You just try to redraw the text. Try changing the size of the font as follows:

Code:

    Font font = g2.getFont().deriveFont(<modified-font-size-changed-by-jslider>);

instead of:

Code:

    Font font = g2.getFont().deriveFont(20f);

You can just have a mapping between JSlider position and font size. Based on the position of JSlider, you can assign a new font size. It should work in that case.

[louiebagz]

Thank you for the inputs...