custom java Swing component Model, UIDelegate, component format

Question

I was given the task to create a custom swing component. I have my component functioning properly in a test application which includes JSlider that is used to zoom in and out on an Image. However I am required to present my custom component in a Model, UIDelegate, and Component class format and I am totally lost on how to convert my code so that it follows this format. Here is the code for my test application.

package test;

import java.awt.*;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;

import javax.swing.*;
import javax.swing.border.EmptyBorder;
import javax.swing.event.*;

import java.io.File;
import java.net.URL;

import javax.imageio.ImageIO;

public class ZoomDemo extends JComponent implements ChangeListener {

JPanel gui;
/**
 * Displays the image.
 */
JLabel imageCanvas;
Dimension size;
double scale = 1.0;
private BufferedImage image;

public ZoomDemo() {
    size = new Dimension(10, 10);
    setBackground(Color.black);
    try {
         image = ImageIO.read(new File("car.jpg"));
    } catch (Exception ex) {
        ex.printStackTrace();
    }
}

public void setImage(Image image) {
    imageCanvas.setIcon(new ImageIcon(image));
}

public void initComponents() {
    if (gui == null) {
        gui = new JPanel(new BorderLayout());
        gui.setBorder(new EmptyBorder(5, 5, 5, 5));
        imageCanvas = new JLabel();
        JPanel imageCenter = new JPanel(new GridBagLayout());
        imageCenter.add(imageCanvas);
        JScrollPane imageScroll = new JScrollPane(imageCenter);
        imageScroll.setPreferredSize(new Dimension(300, 100));
        gui.add(imageScroll, BorderLayout.CENTER);
    }
}

public Container getGui() {
    initComponents();
    return gui;
}

public void stateChanged(ChangeEvent e) {
    int value = ((JSlider) e.getSource()).getValue();
    scale = value / 100.0;
    paintImage();
}

protected void paintImage() {

    int imageWidth = image.getWidth();
    int imageHeight = image.getHeight();
    BufferedImage bi = new BufferedImage(
            (int)(imageWidth*scale), 
            (int)(imageHeight*scale), 
            image.getType());
    Graphics2D g2 = bi.createGraphics();
    g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
            RenderingHints.VALUE_ANTIALIAS_ON);
    AffineTransform at = AffineTransform.getTranslateInstance(0, 0);
    at.scale(scale, scale);
    g2.drawRenderedImage(image, at);
    setImage(bi);
}

public Dimension getPreferredSize() {
    int w = (int) (scale * size.width);
    int h = (int) (scale * size.height);
    return new Dimension(w, h);
}

private JSlider getControl() {
    JSlider slider = new JSlider(JSlider.HORIZONTAL, 1, 500, 50);
    slider.setMajorTickSpacing(50);
    slider.setMinorTickSpacing(25);
    slider.setPaintTicks(true);
    slider.setPaintLabels(true);
    slider.addChangeListener(this);
    return slider;
}

public static void main(String[] args) {
    ZoomDemo app = new ZoomDemo();
    JFrame frame = new JFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setContentPane(app.getGui());
    app.setImage(app.image);

    // frame.getContentPane().add(new JScrollPane(app));  
    frame.getContentPane().add(app.getControl(), "Last");
    frame.setSize(700, 500);
    frame.setLocation(200, 200);
    frame.setVisible(true);
}
}

The following code is the class format i need to follow

Component Class

package component;

import javax.swing.JComponent;

import javax.swing.JSlider;
import javax.swing.plaf.ComponentUI;

public class ProgressBar extends JComponent {

public static ComponentUI createUI(JComponent c) {
    return new ZoomUI();
}

public void installUI(JComponent c){



}

public void uninstallUI (JComponent c){

}
}

Model CLass

public class ZoomModel extends JSLider  {



}

UIDelegate Class

public class ZoomUI extends ComponentUI implements ChangeListener{

}

Any help on how I can implement my custom component in this format would be greatly appreciated. I am very new to Swing and documentation I have found on custom components has been very confusing and of little help.

test application

package test;

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;

import javax.swing.*;
import javax.swing.border.EmptyBorder;
import javax.swing.border.LineBorder;
import javax.swing.event.*;

import java.io.File;
import java.net.URL;

import javax.imageio.ImageIO;

import component.ZoomComponent;

public class ZoomDemo  extends JPanel implements PropertyChangeListener, ActionListener {

ZoomComponent zoomer;
JPanel board;
private BufferedImage image;

public ZoomDemo( ) {
    super(true);  
    setLayout(new BorderLayout( )); 
    board = new JPanel(true); 
    board.setPreferredSize(new Dimension(300, 300)); 
    board.setBorder(new LineBorder(Color.black, 5));

    zoomer = new ZoomComponent();
    add(board, BorderLayout.NORTH);
    add(zoomer, BorderLayout.SOUTH);



}


@Override
public void actionPerformed(ActionEvent arg0) {
    // TODO Auto-generated method stub

}

@Override
public void propertyChange(PropertyChangeEvent arg0) {
    // TODO Auto-generated method stub

}

public static void main(String[] args) {

    UIManager.getDefaults().put("ZoomComponentUI", "component.BasicZoomUI");
    ZoomDemo s= new ZoomDemo();
    JFrame frame = new JFrame("Sample Sketch Application"); 
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
    frame.setContentPane(s); 
    frame.pack( ); 
    frame.setVisible(true);
}

}

Answer 1

Okay, so that was a fun adventure into parts of the API I don't use :), start by having a read through How to Write a Custom Swing Component and it's associated links, this will give you the ground work to understand what is about to happen...

Model

The Interface

Personally, I always start with an interface, life is better with interfaces and it gives you more flexibility. Now, which model should you extend from (based on your requirements)...?

Well, the best choice I could find was the BoundedRangeModel, which is also used by the JSlider...this actually means that I can not only pass this model to the view, but to a JSlider and without any extra work, have the slider change the image!! Win-Win

import java.awt.Dimension;
import java.awt.Image;
import javax.swing.BoundedRangeModel;

public interface ZoomModel extends BoundedRangeModel {

    public Image getImage();

    public Dimension getScaledSize();

}

The Abstract

Next, I like to make an abstract version, this is where I put "common" functionality, which is likely to be the same for most implementations, in this case, it might not be required, but I'm finckle like this...

import java.awt.Dimension;
import java.awt.Image;
import javax.swing.DefaultBoundedRangeModel;

public abstract class AbstractZoomModel extends DefaultBoundedRangeModel implements ZoomModel {

    public AbstractZoomModel() {
        super(100, 0, 0, 200);
    }

    @Override
    public Dimension getScaledSize() {
        Dimension size = new Dimension(0, 0);
        Image image = getImage();
        if (image != null) {
            double scale = getValue() / 100d;
            size.width = (int) Math.round(image.getWidth(null) * scale);
            size.height = (int) Math.round(image.getHeight(null) * scale);

        }
        return size;
    }

}

So, you can see here, I've defined some basic properties, a starting zoom level of 100, a max level of 200 and a minimum level of 0, plus I've implemented the getScaledSize, which is used a bit and makes life easier...

The Default...

Now, because we like been nice, we provide a "default" implementation of the model. This is pretty basic in that all it does it takes a reference to an image...

import java.awt.Image;

public class DefaultZoomModel extends AbstractZoomModel {
    Image image;

    public DefaultZoomModel(Image image) {
        this.image = image;
    }

    @Override
    public Image getImage() {
        return image;
    }

}

You could create implementations that download images from an URL for example...

The View

Okay, this is the actually component itself, which gets added to your UI. It contains the basic functionality need to construct and prepare the UI delegate and manage the model. The key thing of interest here is the use of the property change support to provide notification of the change to the model, this is important as you will see...

import java.awt.Color;
import java.awt.Dimension;
import javax.swing.JComponent;
import javax.swing.UIManager;

public class ZoomComponent extends JComponent {

    private static final String uiClassID = "ZoomComponentUI";
    private ZoomModel model;

    public ZoomComponent() {
        setBackground(Color.black);
        setFocusable(true);
        updateUI();
    }

    public void setModel(ZoomModel newModel) {
        if (model != newModel) {
            ZoomModel old = model;
            this.model = newModel;
            firePropertyChange("model", old, newModel);
        }
    }

    public ZoomModel getModel() {
        return model;
    }

    @Override
    public Dimension getPreferredSize() {
        ZoomModel model = getModel();
        Dimension size = new Dimension(100, 100);
        if (model != null) {
            size = model.getScaledSize();
        }
        return size;
    }

    public void setUI(BasicZoomUI ui) {
        super.setUI(ui);
    }

    @Override
    public void updateUI() {
        if (UIManager.get(getUIClassID()) != null) {
            ZoomUI ui = (ZoomUI) UIManager.getUI(this);
            setUI(ui);
        } else {
            setUI(new BasicZoomUI());
        }
    }

    public BasicZoomUI getUI() {
        return (BasicZoomUI) ui;
    }

    @Override
    public String getUIClassID() {
        return uiClassID;
    }
}

The UI Delegate

Now the other fun stuff...If we follow standard convention, you would normally provide an abstract concept of the UI delegate, for example...

import javax.swing.plaf.ComponentUI;

public abstract class ZoomUI extends ComponentUI {       
}

From this, other delegates will grow...

Basic UI Delegate

Convention would normally suggest you provide a "basic" implementation, doing a lot of the heavy lifting, but allowing other implementations the opportunity to jump in change things to there likely

import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseWheelEvent;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import javax.swing.AbstractAction;
import javax.swing.Action;
import javax.swing.ActionMap;
import javax.swing.InputMap;
import javax.swing.JComponent;
import javax.swing.KeyStroke;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import javax.swing.plaf.ComponentUI;

public class BasicZoomUI extends ZoomUI {

    private ZoomComponent zoomComponent;
    private MouseAdapter mouseHandler;
    private ChangeListener changeHandler;

    private Action zoomIn;
    private Action zoomOut;
    private PropertyChangeListener propertyChangeHandler;

    protected ChangeListener getChangeHandler() {
        if (changeHandler == null) {
            changeHandler = new ChangeHandler();
        }
        return changeHandler;
    }

    protected void installMouseListener() {
        mouseHandler = new MouseAdapter() {

            @Override
            public void mouseClicked(MouseEvent e) {
                zoomComponent.requestFocusInWindow();
            }

            @Override
            public void mouseWheelMoved(MouseWheelEvent e) {
                int amount = e.getWheelRotation();
                ZoomModel model = zoomComponent.getModel();
                if (model != null) {

                    int value = model.getValue();
                    model.setValue(value + amount);

                }
            }

        };
        zoomComponent.addMouseListener(mouseHandler);
        zoomComponent.addMouseWheelListener(mouseHandler);

    }

    protected void installModelPropertyChangeListener() {

        propertyChangeHandler = new PropertyChangeListener() {
            @Override
            public void propertyChange(PropertyChangeEvent evt) {
                ZoomModel old = (ZoomModel) evt.getOldValue();
                if (old != null) {
                    old.removeChangeListener(getChangeHandler());
                }
                ZoomModel newValue = (ZoomModel) evt.getNewValue();
                if (newValue != null) {
                    newValue.addChangeListener(getChangeHandler());
                }
            }
        };

        zoomComponent.addPropertyChangeListener("model", propertyChangeHandler);

    }

    protected void installKeyBindings() {

        zoomIn = new ZoomInAction();
        zoomOut = new ZoomOutAction();

        InputMap inputMap = zoomComponent.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW);
        inputMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_ADD, 0), "zoomIn");
        inputMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_SUBTRACT, 0), "zoomOut");
        inputMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_PLUS, 0), "zoomIn");
        inputMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_MINUS, 0), "zoomOut");

        ActionMap actionMap = zoomComponent.getActionMap();
        actionMap.put("zoomIn", zoomIn);
        actionMap.put("zoomOut", zoomOut);
    }

    protected void installModelChangeListener() {

        ZoomModel model = getModel();
        if (model != null) {
            model.addChangeListener(getChangeHandler());
        }

    }

    @Override
    public void installUI(JComponent c) {

        zoomComponent = (ZoomComponent) c;

        installMouseListener();
        installModelPropertyChangeListener();
        installKeyBindings();
        installModelChangeListener();

    }

    protected void uninstallModelChangeListener() {

        getModel().removeChangeListener(getChangeHandler());

    }

    protected void uninstallKeyBindings() {

        InputMap inputMap = zoomComponent.getInputMap(JComponent.WHEN_FOCUSED);
        inputMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_ADD, 0), "donothing");
        inputMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_SUBTRACT, 0), "donothing");
        inputMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_PLUS, 0), "donothing");
        inputMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_MINUS, 0), "donothing");

        AbstractAction blank = new AbstractAction() {
            @Override
            public void actionPerformed(ActionEvent e) {
            }
        };

        ActionMap actionMap = zoomComponent.getActionMap();
        actionMap.put("zoomIn", blank);
        actionMap.put("zoomOut", blank);

    }

    protected void uninstallModelPropertyChangeListener() {

        zoomComponent.removePropertyChangeListener(propertyChangeHandler);
        propertyChangeHandler = null;

    }

    protected void uninstallMouseListener() {

        zoomComponent.removeMouseWheelListener(mouseHandler);
        mouseHandler = null;

    }

    @Override
    public void uninstallUI(JComponent c) {

        uninstallModelChangeListener();
        uninstallModelPropertyChangeListener();
        uninstallKeyBindings();
        uninstallMouseListener();

        mouseHandler = null;
        zoomComponent = null;

    }

    @Override
    public void paint(Graphics g, JComponent c) {
        super.paint(g, c);
        paintImage(g);
    }

    protected void paintImage(Graphics g) {
        if (zoomComponent != null) {
            ZoomModel model = zoomComponent.getModel();
            Image image = model.getImage();
            Dimension size = model.getScaledSize();
            int x = (zoomComponent.getWidth() - size.width) / 2;
            int y = (zoomComponent.getHeight() - size.height) / 2;
            g.drawImage(image, x, y, size.width, size.height, zoomComponent);
        }
    }

    public static ComponentUI createUI(JComponent c) {
        return new BasicZoomUI();
    }

    protected ZoomModel getModel() {

        return zoomComponent == null ? null : zoomComponent.getModel();

    }

    protected class ChangeHandler implements ChangeListener {

        @Override
        public void stateChanged(ChangeEvent e) {
            zoomComponent.revalidate();
            zoomComponent.repaint();
        }

    }

    protected class ZoomAction extends AbstractAction {

        private int delta;