Java 中文官方教程 2022 版（二十五）（1）

public class ContainerEventDemo ... implements ContainerListener ... {
    *...//where initialization occurs:*
        buttonPanel = new JPanel(new GridLayout(1,1));
        buttonPanel.addContainerListener(this);
    ...
    public void componentAdded(ContainerEvent e) {
        displayMessage(" added to ", e);
    }
    public void componentRemoved(ContainerEvent e) {
        displayMessage(" removed from ", e);
    }
    void displayMessage(String action, ContainerEvent e) {
        display.append(((JButton)e.getChild()).getText()
                       + " was"
                       + action
                       + e.getContainer().getClass().getName()
                       + newline);
    }
    ...
}

public class DocumentEventDemo ... {
    *...//where initialization occurs:*
    textField = new JTextField(20);
    textField.addActionListener(new MyTextActionListener());
    textField.getDocument().addDocumentListener(new MyDocumentListener());
    textField.getDocument().putProperty("name", "Text Field");
    textArea = new JTextArea();
    textArea.getDocument().addDocumentListener(new MyDocumentListener());
    textArea.getDocument().putProperty("name", "Text Area");
    ...
class MyDocumentListener implements DocumentListener {
    String newline = "\n";
    public void insertUpdate(DocumentEvent e) {
        updateLog(e, "inserted into");
    }
    public void removeUpdate(DocumentEvent e) {
        updateLog(e, "removed from");
    }
    public void changedUpdate(DocumentEvent e) {
        //Plain text components do not fire these events
    }
    public void updateLog(DocumentEvent e, String action) {
        Document doc = (Document)e.getDocument();
        int changeLength = e.getLength();
        displayArea.append(
            changeLength + " character" +
            ((changeLength == 1) ? " " : "s ") +
            action + doc.getProperty("name") + "." + newline +
            "  Text length = " + doc.getLength() + newline);
    }
}

public class FocusEventDemo ... implements FocusListener ... {
    public FocusEventDemo() {
        ...
        JTextField textField = new JTextField("A TextField");
        textField.addFocusListener(this);
        ...
        JLabel label = new JLabel("A Label");
        label.addFocusListener(this);
        ...
        JComboBox comboBox = new JComboBox(vector);
        comboBox.addFocusListener(this);
        ...
        JButton button = new JButton("A Button");
        button.addFocusListener(this);
        ...
        JList list = new JList(listVector);
        list.setSelectedIndex(1); //It's easier to see the focus change
                                  //if an item is selected.
        list.addFocusListener(this);
        JScrollPane listScrollPane = new JScrollPane(list);
        ...
        //Set up the area that reports focus-gained and focus-lost events.
        display = new JTextArea();
        display.setEditable(false);
        //The method setRequestFocusEnabled prevents a
        //component from being clickable, but it can still
        //get the focus through the keyboard - this ensures
        //user accessibility.
        display.setRequestFocusEnabled(false);
        display.addFocusListener(this);
        JScrollPane displayScrollPane = new JScrollPane(display);
        ...
    }
    ...
    public void focusGained(FocusEvent e) {
        displayMessage("Focus gained", e);
    }
    public void focusLost(FocusEvent e) {
        displayMessage("Focus lost", e);
    }
    void displayMessage(String prefix, FocusEvent e) {
        display.append(prefix
                       + (e.isTemporary() ? " (temporary):" : ":")
                       +  e.getComponent().getClass().getName()
                       + "; Opposite component: " 
                       + (e.getOppositeComponent() != null ?
                          e.getOppositeComponent().getClass().getName() : "null")
                       + newline); 
    }
    ...
}

public class InternalFrameEventDemo ...
                     implements InternalFrameListener ... {
    ...
    public void internalFrameClosing(InternalFrameEvent e) {
        displayMessage("Internal frame closing", e);
    }
    public void internalFrameClosed(InternalFrameEvent e) {
        displayMessage("Internal frame closed", e);
        listenedToWindow = null;
    }
    public void internalFrameOpened(InternalFrameEvent e) {
        displayMessage("Internal frame opened", e);
    }
    public void internalFrameIconified(InternalFrameEvent e) {
        displayMessage("Internal frame iconified", e);
    }
    public void internalFrameDeiconified(InternalFrameEvent e) {
        displayMessage("Internal frame deiconified", e);
    }
    public void internalFrameActivated(InternalFrameEvent e) {
        displayMessage("Internal frame activated", e);
    }
    public void internalFrameDeactivated(InternalFrameEvent e) {
        displayMessage("Internal frame deactivated", e);
    }
    void displayMessage(String prefix, InternalFrameEvent e) {
        String s = prefix + ": " + e.getSource(); 
        display.append(s + newline);
    }
    public void actionPerformed(ActionEvent e) {
        if (SHOW.equals(e.getActionCommand())) {
            ...
            if (listenedToWindow == null) {
                listenedToWindow = new JInternalFrame("Event Generator",
                                                      true,  //resizable
                                                      true,  //closable
                                                      true,  //maximizable
                                                      true); //iconifiable
                //We want to reuse the internal frame, so we need to
                //make it hide (instead of being disposed of, which is
                //the default) when the user closes it.
                listenedToWindow.setDefaultCloseOperation(
                                        WindowConstants.HIDE_ON_CLOSE);
                listenedToWindow.addInternalFrameListener(this);
                ...
            }
        } 
        ...
    }
}