如何使用AffineTransform缩放Swing组件？

Question

I am trying to create a panel where I will have the possibility to zoom on custom made JComponent objects. I have tried to call the scale() method in the AffineTransform class with different values, but I have not succeeded. My objects just disappear.

Below is my component that is used in the main frame class. Everything works except the zooming. Could some of you explain the concepts of AffineTransform. I don´t think the JavaDoc explenation is enough for me.

Here is an executable SSCCE:

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.HeadlessException;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.awt.event.MouseWheelEvent;
import java.awt.event.MouseWheelListener;
import java.awt.geom.AffineTransform;
import javax.swing.JComponent;
import javax.swing.JFrame;


public class JavaApplication1 extends JFrame {

    public static void main(String[] args) {
        new JavaApplication1();
    }

    private MyComponent myComponent = new MyComponent();

    public JavaApplication1() throws HeadlessException {
        this.setSize(400,400);
        this.setVisible(true);
        this.add(myComponent);
    }
    class MyComponent extends JComponent {

        private int x, y;
        private double scale=1;
        private MouseAdapter mouseAdapter = new MouseAdapter();
        private AffineTransform transform = new AffineTransform();

        public MyComponent() {
            this.addMouseListener(mouseAdapter);
            this.addMouseWheelListener(mouseAdapter);
            this.addMouseMotionListener(mouseAdapter);
        }

        @Override
        protected void paintComponent(Graphics g) {
            Graphics2D g2 = (Graphics2D)g;
            g2.setColor(Color.DARK_GRAY);
            g2.fillRect(0, 0, 400, 400);
            g2.setColor(Color.RED);
            g2.setTransform(transform);

            transform.scale(scale, scale); 
            g2.drawString("My String!", x, y);
        }

        private class MouseAdapter implements MouseWheelListener, MouseListener, MouseMotionListener {

            @Override
            public void mouseWheelMoved(MouseWheelEvent e) {
                if(e.getWheelRotation() == 1) {
                    scale+=0.1;
                }else {
                    scale-=0.1;
                }
            }

            @Override
            public void mouseClicked(MouseEvent e) {
            }

            @Override
            public void mousePressed(MouseEvent e) {            
            }

            @Override
            public void mouseReleased(MouseEvent e) {
            }

            @Override
            public void mouseEntered(MouseEvent e) {
            }

            @Override
            public void mouseExited(MouseEvent e) {
            }

            @Override
            public void mouseDragged(MouseEvent e) {
                x = e.getX();
                y = e.getY();
                repaint();
            }

            @Override
            public void mouseMoved(MouseEvent e) {
            }        
        }
    }   
}

Answer 1

transform.scale accepts two double parameters, one for the x axis and the other for the y axis, being 1 the neutral value (no change in scale), and the two parameters the multipliers.

Ex: transform.scale(2,2) will show the component twice as big, while transform.scale(0.5,0.5) will show it twice as small.

http://docs.oracle.com/javase/6/docs/api/java/awt/geom/AffineTransform.html#scale(double, double)