您的问题之前已经提到过，它的解决方案也是如此。您必须从 PropertyChangeListener 中实际添加或删除组件到您的观察者面板。调用revalidate()andrepaint()不会神奇地添加或删除组件，除非您在调用这些方法之前明确执行此操作。
例如：
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Component;
import java.awt.Font;
import java.awt.GridLayout;
import java.awt.Point;
import java.awt.event.ActionEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.beans.IndexedPropertyChangeEvent;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import javax.swing.*;
import javax.swing.event.SwingPropertyChangeSupport;
public class ListenToTest {
public static final String[] ITEMS = {"Sunday", "Monday", "Tuesday", "Wednesday",
"Thursday", "Friday", "Saturday"};
private JPanel mainPanel = new JPanel();
private ObserverPanel observerPanel = new ObserverPanel();
private ListenToModel model = new ListenToModel();
public ListenToTest() {
observerPanel.setModel(model);
for (String item : ITEMS) {
model.addItem(item);
}
JPanel btnPanel = new JPanel();
btnPanel.add(new JButton(new AddAction("Add")));
btnPanel.add(new JButton(new RemoveAction("Remove")));
mainPanel.setLayout(new BorderLayout());
mainPanel.add(new JScrollPane(observerPanel.getMainComponent()));
mainPanel.add(btnPanel, BorderLayout.PAGE_END);
}
public JComponent getMainComponent() {
return mainPanel;
}
private class AddAction extends AbstractAction {
public AddAction(String title) {
super(title);
}
@Override
public void actionPerformed(ActionEvent arg0) {
String text = JOptionPane.showInputDialog(mainPanel, "Enter a String");
if (text != null) {
model.addItem(text);
}
}
}
private class RemoveAction extends AbstractAction {
public RemoveAction(String title) {
super(title);
}
@Override
public void actionPerformed(ActionEvent arg0) {
int index = observerPanel.getSelectedIndex();
if (index >= 0) {
model.removeItem(index);
}
}
}
private static void createAndShowGui() {
ListenToTest mainPanel = new ListenToTest();
JFrame frame = new JFrame("ListenToModelTest");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(mainPanel.getMainComponent());
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
class ObserverPanel {
public static final Font LABEL_FONT = new Font(Font.SANS_SERIF, Font.BOLD, 18);
protected static final Color SELECTED_COLOR = new Color(150, 150, 255);
private JPanel mainPanel = new JPanel();
private ListenToModel model;
private GridLayout gridLayout = new GridLayout(0, 1);
private int selectedIndex = -1;
public ObserverPanel() {
mainPanel.setLayout(gridLayout);
mainPanel.addMouseListener(new MouseAdapter() {
@Override
public void mousePressed(MouseEvent e) {
Point p = e.getPoint();
Component[] components = mainPanel.getComponents();
for (int i = 0; i < components.length; i++) {
if (mainPanel.getComponentAt(p).equals(components[i])) {
selectedIndex = i;
components[i].setBackground(SELECTED_COLOR);
} else {
components[i].setBackground(null);
}
}
}
});
}
public int getSelectedIndex() {
return selectedIndex;
}
public void setModel(ListenToModel model) {
this.model = model;
model.addPropertyChangeListener(new ObserverPanelListener());
}
public JComponent getMainComponent() {
return mainPanel;
}
private class ObserverPanelListener implements PropertyChangeListener {
public void propertyChange(PropertyChangeEvent evt) {
if (evt.getPropertyName().equals(ListenToModel.ADD)) {
JLabel label = createLabel(evt);
for (Component comp : mainPanel.getComponents()) {
comp.setBackground(null);
}
int index = ((IndexedPropertyChangeEvent)evt).getIndex();
mainPanel.add(label, index);
label.setBackground(SELECTED_COLOR);
selectedIndex = index;
} else if (evt.getPropertyName().equals(ListenToModel.REMOVE)) {
int index = ((IndexedPropertyChangeEvent)evt).getIndex();
mainPanel.remove(index);
for (Component comp : mainPanel.getComponents()) {
comp.setBackground(null);
}
selectedIndex = -1;
} else if (evt.getPropertyName().equals(ListenToModel.REMOVE_ALL)) {
mainPanel.removeAll();
selectedIndex = -1;
}
mainPanel.revalidate();
mainPanel.repaint();
}
private JLabel createLabel(PropertyChangeEvent evt) {
String newValue = evt.getNewValue().toString();
JLabel label = new JLabel(newValue);
label.setFont(LABEL_FONT);
int eb = 20;
label.setBorder(BorderFactory.createCompoundBorder(BorderFactory.createLineBorder(Color.blue),
BorderFactory.createEmptyBorder(eb , eb, eb, eb)));
label.setFocusable(true);
label.setOpaque(true);
return label;
}
}
}
class ListenToModel implements Iterable<String> {
public static final String ADD = "add";
public static final String REMOVE = "remove";
public static final String REMOVE_ALL = "remove all";
private SwingPropertyChangeSupport spcSupport = new SwingPropertyChangeSupport(
this);
private List<String> modelNucleus = new ArrayList<String>();
public void addItem(String item) {
modelNucleus.add(item);
spcSupport.fireIndexedPropertyChange(ADD, modelNucleus.size() - 1, null,
item);
}
public void addItem(int index, String item) {
if (index < 0 || index > modelNucleus.size()) {
// TODO: throw an exception
} else {
modelNucleus.add(index, item);
spcSupport.fireIndexedPropertyChange(REMOVE, index, null, item);
}
}
public void removeItem(int index) {
if (index < 0 || index >= modelNucleus.size()) {
// TODO: throw an exception
} else {
String oldValue = modelNucleus.remove(index);
spcSupport.fireIndexedPropertyChange(REMOVE, index, oldValue, null);
}
}
public void removeAll() {
modelNucleus.clear();
spcSupport.firePropertyChange(REMOVE_ALL, null, null);
}
public void addPropertyChangeListener(PropertyChangeListener listener) {
spcSupport.addPropertyChangeListener(listener);
}
public void removePropertyChangeListener(PropertyChangeListener listener) {
spcSupport.removePropertyChangeListener(listener);
}
@Override
public Iterator<String> iterator() {
return modelNucleus.iterator();
}
}