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;
public ZoomAction(int delta) {
this.delta = delta;
}
@Override
public void actionPerformed(ActionEvent e) {
ZoomModel model = getModel();
if (model != null) {
model.setValue(model.getValue() + delta);
}
}
}
protected class ZoomOutAction extends ZoomAction {
public ZoomOutAction() {
super(-5);
}
}
protected class ZoomInAction extends ZoomAction {
public ZoomInAction() {
super(5);
}
}
}
From here you could go and devise platform specific implementations, but I've decided to stick with the basic delegate...
Putting it all together
If that wasn't enough, before you can use any of it, you must install the delegate...
UIManager.getDefaults().put("ZoomComponentUI", "your.awesome.package.name.BasicZoomUI");
nb: Change your.awesome.package.name to reflect your actual package name...
Runnable Example
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JSlider;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class TestZoom100 {
public static void main(String[] args) {
new TestZoom100();
}
public TestZoom100() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
UIManager.getDefaults().put("ZoomComponentUI", "your.awesome.package.name.BasicZoomUI");
try {
DefaultZoomModel model = new DefaultZoomModel(ImageIO.read(new File("/your/awesome/image.jpg")));
model.setValue(50);
ZoomComponent zoomComp = new ZoomComponent();
zoomComp.setModel(model);
JSlider slider = new JSlider(model);
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new JScrollPane(zoomComp));
frame.add(slider, BorderLayout.SOUTH);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
} catch (IOException exp) {
exp.printStackTrace();
}
}
});
}
}
Don't forget to change the package name for the BasicZoomUI to the package name you have it stored in and actually specify a image file ;)
