Java基础之扩展GUI——使用字体对话框（Sketcher 5 displaying a font dialog）

控制台程序。

为了可以选择系统支持的字体，我们定义了一个FontDialog类：

 // Class to define a dialog to choose a font
 import java.awt.*;
 import javax.swing.*;
 import java.awt.event.*;
 import javax.swing.event.*;
 import static Constants.SketcherConstants.*;

 @SuppressWarnings("serial")
 class FontDialog extends JDialog
                  implements ActionListener,                            // For buttons etc.
                             ListSelectionListener,                     // For list box
                             ChangeListener {                           // For the spinner
   // Constructor
   public FontDialog(SketcherFrame window) {
     // Call the base constructor to create a modal dialog
     super(window, "Font Selection", true);
     font = window.getFont();                                           // Get the current font

   // Create the dialog button panel
   JPanel buttonPane = new JPanel();                                    // Create a panel to hold buttons

   // Create and add the buttons to the buttonPane
   buttonPane.add(ok = createButton("OK"));                             // Add the OK button
   buttonPane.add(cancel = createButton("Cancel"));                     // Add the Cancel button
   getContentPane().add(buttonPane, BorderLayout.SOUTH);                // Add pane

     // Code to create the data input panel
     JPanel dataPane = new JPanel();                                    // Create the data entry panel
     dataPane.setBorder(BorderFactory.createCompoundBorder(             // Pane border
                        BorderFactory.createLineBorder(Color.BLACK),
                        BorderFactory.createEmptyBorder(5, 5, 5, 5)));
     GridBagLayout gbLayout = new GridBagLayout();                      // Create the layout
     dataPane.setLayout(gbLayout);                                      // Set the pane layout
     GridBagConstraints constraints = new GridBagConstraints();

     // Create the font choice and add it to the input panel
     JLabel label = new JLabel("Choose a Font");
     constraints.fill = GridBagConstraints.HORIZONTAL;
     constraints.gridwidth = GridBagConstraints.REMAINDER;
     gbLayout.setConstraints(label, constraints);
     dataPane.add(label);

     // Code to set up font list choice component
     GraphicsEnvironment e = GraphicsEnvironment.getLocalGraphicsEnvironment();
     String[] fontNames = e.getAvailableFontFamilyNames();              // Get font names

     fontList = new JList<>(fontNames);                                 // Create list of font names
     fontList.setValueIsAdjusting(true);                                // single event selection
     fontList.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
     fontList.setSelectedValue(font.getFontName(),true);
     fontList.addListSelectionListener(this);
     fontList.setToolTipText("Choose a font");
     JScrollPane chooseFont = new JScrollPane(fontList);                // Scrollable list
     chooseFont.setMinimumSize(new Dimension(400,100));
     chooseFont.setWheelScrollingEnabled(true);                         // Enable mouse wheel scroll

     // Panel to display font sample
     JPanel display = new JPanel(true);
     fontDisplay = new JLabel("Sample Size: x X y Y z Z");
     fontDisplay.setFont(font);
     fontDisplay.setPreferredSize(new Dimension(350,100));
     display.add(fontDisplay);

     //Create a split pane with font choice at the top and font display at the bottom
     JSplitPane splitPane = new JSplitPane(JSplitPane.VERTICAL_SPLIT,
                                true,
                                chooseFont,
                                display);
     gbLayout.setConstraints(splitPane, constraints);                   // Split pane constraints
     dataPane.add(splitPane);                                           // Add to the data pane

     // Set up the size choice using a spinner
     JPanel sizePane = new JPanel(true);                                // Pane for size choices
     label = new JLabel("Choose point size: ");                         // Prompt for point size
     sizePane.add(label);                                               // Add the prompt

     chooseSize = new JSpinner(new SpinnerNumberModel(font.getSize(),
                                   POINT_SIZE_MIN, POINT_SIZE_MAX, POINT_SIZE_STEP));
     chooseSize.setValue(font.getSize());                               // Set current font size
     chooseSize.addChangeListener(this);
     sizePane.add(chooseSize);

      // Add spinner to pane
     gbLayout.setConstraints(sizePane, constraints);                    // Set pane constraints
     dataPane.add(sizePane);                                            // Add the pane

     // Set up style options using radio buttons
     bold = new JRadioButton("Bold", (font.getStyle() & Font.BOLD) > 0);
     italic = new JRadioButton("Italic", (font.getStyle() & Font.ITALIC) > 0);
     bold.addItemListener(new StyleListener(Font.BOLD));                // Add button listeners
     italic.addItemListener(new StyleListener(Font.ITALIC));
     JPanel stylePane = new JPanel(true);                               // Create style pane
     stylePane.add(bold);                                               // Add buttons
     stylePane.add(italic);                                             // to style pane...
     gbLayout.setConstraints(stylePane, constraints);                   // Set pane constraints
     dataPane.add(stylePane);                                           // Add the pane

     getContentPane().add(dataPane, BorderLayout.CENTER);
     pack();
     setVisible(false);
   }

   // Create a dialog button
   JButton createButton(String label) {
     JButton button = new JButton(label);                               // Create the button
     button.setPreferredSize(new Dimension(80,20));                     // Set the size
     button.addActionListener(this);                                    // Listener is the dialog
     return button;                                                     // Return the button
   }

   // Handler for button events
   public void actionPerformed(ActionEvent e) {
     if(e.getSource()== ok)  {                                           // If it's the OK button
       ((SketcherFrame)getOwner()).setFont(font);                        // ...set selected font
     } else {
       font = ((SketcherFrame)getOwner()).getFont();                     // Restore the current font
       fontDisplay.setFont(font);
       chooseSize.setValue(font.getSize());                              // Restore the point size
       fontList.setSelectedValue(font.getName(),true);
       int style = font.getStyle();
       bold.setSelected((style & Font.BOLD) > 0);                        // Restore the
       italic.setSelected((style & Font.ITALIC) > 0);                    // style options
     }
     // Now hide the dialog - for ok or cancel
     setVisible(false);
   }

   // List selection listener method
   public void valueChanged(ListSelectionEvent e) {
     if(!e.getValueIsAdjusting()) {
       font = new Font(fontList.getSelectedValue(), font.getStyle(), font.getSize());
       fontDisplay.setFont(font);
       fontDisplay.repaint();
     }
   }

   // Handle spinner state change events
   public void stateChanged(ChangeEvent e) {
     int fontSize = ((Number)(((JSpinner)e.getSource()).getValue())).intValue();
     font = font.deriveFont((float)fontSize);
     fontDisplay.setFont(font);
     fontDisplay.repaint();
   }

   // Iner class defining listeners for radio buttons
   class StyleListener implements ItemListener {
     public StyleListener(int style) {
       this.style = style;
     }

     // Event handler for font style changes
     public void itemStateChanged(ItemEvent e) {
       int fontStyle = font.getStyle();
       if(e.getStateChange()==ItemEvent.SELECTED) {                     // If style was selected
         fontStyle |= style;                                            // turn it on in the font style
       } else {
         fontStyle &= ~style;                                           // otherwise turn it off
       }
       font = font.deriveFont(fontStyle);                               // Get a new font
       fontDisplay.setFont(font);                                       // Change the label font
       fontDisplay.repaint();                                           // repaint
     }
      private int style;                                                // Style for this listener
   }

   private JList<String> fontList;                                      // Font list
   private JButton ok;                                                  // OK button
   private JButton cancel;                                              // Cancel button
   private JRadioButton bold;                                           // Bold style button
   private JRadioButton italic;                                         // Italic style button
   private Font font;                                                   // Currently selected font
   private JSpinner chooseSize;                                         // Font size options
   private JLabel fontDisplay;                                          // Font sample
 }

然后在SketcherFrame中添加选择字体的菜单项：

 // Frame for the Sketcher application
 import javax.swing.*;
 import javax.swing.border.*;
 import java.awt.event.*;
 import java.awt.*;

 import static java.awt.event.InputEvent.*;
 import static java.awt.Color.*;
 import static Constants.SketcherConstants.*;
 import static javax.swing.Action.*;

 @SuppressWarnings("serial")
 public class SketcherFrame extends JFrame implements ActionListener {
   // Constructor
   public SketcherFrame(String title, Sketcher theApp) {
     setTitle(title);                                                    // Set the window title
     this.theApp = theApp;                                               // Save app. object reference
     setJMenuBar(menuBar);                                               // Add the menu bar to the window
     setDefaultCloseOperation(EXIT_ON_CLOSE);                            // Default is exit the application

     createFileMenu();                                                   // Create the File menu
     createElementMenu();                                                // Create the element menu
     createColorMenu();                                                  // Create the element menu
     JMenu optionsMenu = new JMenu("Options");                           // Create options menu
     optionsMenu.setMnemonic('O');                                       // Create shortcut
     menuBar.add(optionsMenu);                                           // Add options to menu bar

     createPopupMenu();                                                  // Create popup

     // Add the font choice item to the options menu
     fontItem = new JMenuItem("Choose font...");
     fontItem.addActionListener(this);
     optionsMenu.add(fontItem);

     fontDlg = new FontDialog(this);                                     // Create the font dialog

     createToolbar();
     toolBar.setRollover(true);

     JMenu helpMenu = new JMenu("Help");                                 // Create Help menu
     helpMenu.setMnemonic('H');                                          // Create Help shortcut

     // Add the About item to the Help menu
     aboutItem = new JMenuItem("About");                                 // Create About menu item
     aboutItem.addActionListener(this);                                  // Listener is the frame
     helpMenu.add(aboutItem);                                            // Add item to menu
     menuBar.add(helpMenu);                                              // Add Help menu to menu bar

     getContentPane().add(toolBar, BorderLayout.NORTH);                  // Add the toolbar
     getContentPane().add(statusBar, BorderLayout.SOUTH);                // Add the statusbar
   }

   // Create File menu item actions
   private void createFileMenuActions() {
     newAction = new FileAction("New", 'N', CTRL_DOWN_MASK);
     openAction = new FileAction("Open", 'O', CTRL_DOWN_MASK);
     closeAction = new FileAction("Close");
     saveAction = new FileAction("Save", 'S', CTRL_DOWN_MASK);
     saveAsAction = new FileAction("Save As...");
     printAction = new FileAction("Print", 'P', CTRL_DOWN_MASK);
     exitAction = new FileAction("Exit", 'X', CTRL_DOWN_MASK);

     // Initialize the array
     FileAction[] actions = {openAction, closeAction, saveAction, saveAsAction, printAction, exitAction};
     fileActions = actions;

     // Add toolbar icons
     newAction.putValue(LARGE_ICON_KEY, NEW24);
     openAction.putValue(LARGE_ICON_KEY, OPEN24);
     saveAction.putValue(LARGE_ICON_KEY, SAVE24);
     saveAsAction.putValue(LARGE_ICON_KEY, SAVEAS24);
     printAction.putValue(LARGE_ICON_KEY, PRINT24);

     // Add menu item icons
     newAction.putValue(SMALL_ICON, NEW16);
     openAction.putValue(SMALL_ICON, OPEN16);
     saveAction.putValue(SMALL_ICON, SAVE16);
     saveAsAction.putValue(SMALL_ICON,SAVEAS16);
     printAction.putValue(SMALL_ICON, PRINT16);

     // Add tooltip text
     newAction.putValue(SHORT_DESCRIPTION, "Create a new sketch");
     openAction.putValue(SHORT_DESCRIPTION, "Read a sketch from a file");
     closeAction.putValue(SHORT_DESCRIPTION, "Close the current sketch");
     saveAction.putValue(SHORT_DESCRIPTION, "Save the current sketch to file");
     saveAsAction.putValue(SHORT_DESCRIPTION, "Save the current sketch to a new file");
     printAction.putValue(SHORT_DESCRIPTION, "Print the current sketch");
     exitAction.putValue(SHORT_DESCRIPTION, "Exit Sketcher");
   }

   // Create the File menu
   private void createFileMenu() {
     JMenu fileMenu = new JMenu("File");                                 // Create File menu
     fileMenu.setMnemonic('F');                                          // Create shortcut
     createFileMenuActions();                                            // Create Actions for File menu item

     // Construct the file drop-down menu
     fileMenu.add(newAction);                                            // New Sketch menu item
     fileMenu.add(openAction);                                           // Open sketch menu item
     fileMenu.add(closeAction);                                          // Close sketch menu item
     fileMenu.addSeparator();                                            // Add separator
     fileMenu.add(saveAction);                                           // Save sketch to file
     fileMenu.add(saveAsAction);                                         // Save As menu item
     fileMenu.addSeparator();                                            // Add separator
     fileMenu.add(printAction);                                          // Print sketch menu item
     fileMenu.addSeparator();                                            // Add separator
     fileMenu.add(exitAction);                                           // Print sketch menu item
     menuBar.add(fileMenu);                                              // Add the file menu
   }

   // Create Element  menu actions
   private void createElementTypeActions() {
     lineAction = new TypeAction("Line", LINE, 'L', CTRL_DOWN_MASK);
     rectangleAction = new TypeAction("Rectangle", RECTANGLE, 'R', CTRL_DOWN_MASK);
     circleAction =  new TypeAction("Circle", CIRCLE,'C', CTRL_DOWN_MASK);
     curveAction = new TypeAction("Curve", CURVE,'U', CTRL_DOWN_MASK);
     textAction = new TypeAction("Text", TEXT,'T', CTRL_DOWN_MASK);

     // Initialize the array
     TypeAction[] actions = {lineAction, rectangleAction, circleAction, curveAction, textAction};
     typeActions = actions;

     // Add toolbar icons
     lineAction.putValue(LARGE_ICON_KEY, LINE24);
     rectangleAction.putValue(LARGE_ICON_KEY, RECTANGLE24);
     circleAction.putValue(LARGE_ICON_KEY, CIRCLE24);
     curveAction.putValue(LARGE_ICON_KEY, CURVE24);
     textAction.putValue(LARGE_ICON_KEY, TEXT24);

     // Add menu item icons
     lineAction.putValue(SMALL_ICON, LINE16);
     rectangleAction.putValue(SMALL_ICON, RECTANGLE16);
     circleAction.putValue(SMALL_ICON, CIRCLE16);
     curveAction.putValue(SMALL_ICON, CURVE16);
     textAction.putValue(SMALL_ICON, TEXT16);

     // Add tooltip text
     lineAction.putValue(SHORT_DESCRIPTION, "Draw lines");
     rectangleAction.putValue(SHORT_DESCRIPTION, "Draw rectangles");
     circleAction.putValue(SHORT_DESCRIPTION, "Draw circles");
     curveAction.putValue(SHORT_DESCRIPTION, "Draw curves");
     textAction.putValue(SHORT_DESCRIPTION, "Draw text");
   }

   // Create the Elements menu
   private void createElementMenu() {
     createElementTypeActions();
     elementMenu = new JMenu("Elements");                                // Create Elements menu
     elementMenu.setMnemonic('E');                                       // Create shortcut
     createRadioButtonDropDown(elementMenu, typeActions, lineAction);
     menuBar.add(elementMenu);                                           // Add the element menu
   }

   // Create Color menu actions
   private void createElementColorActions() {
     redAction = new ColorAction("Red", RED, 'R', CTRL_DOWN_MASK|ALT_DOWN_MASK);
     yellowAction = new ColorAction("Yellow", YELLOW, 'Y', CTRL_DOWN_MASK|ALT_DOWN_MASK);
     greenAction = new ColorAction("Green", GREEN, 'G', CTRL_DOWN_MASK|ALT_DOWN_MASK);
     blueAction = new ColorAction("Blue", BLUE, 'B', CTRL_DOWN_MASK|ALT_DOWN_MASK);

     // Initialize the array
     ColorAction[] actions = {redAction, greenAction, blueAction, yellowAction};
     colorActions = actions;

     // Add toolbar icons
     redAction.putValue(LARGE_ICON_KEY, RED24);
     greenAction.putValue(LARGE_ICON_KEY, GREEN24);
     blueAction.putValue(LARGE_ICON_KEY, BLUE24);
     yellowAction.putValue(LARGE_ICON_KEY, YELLOW24);

     // Add menu item icons
     redAction.putValue(SMALL_ICON, RED16);
     greenAction.putValue(SMALL_ICON, GREEN16);
     blueAction.putValue(SMALL_ICON, BLUE16);
     yellowAction.putValue(SMALL_ICON, YELLOW16);

     // Add tooltip text
     redAction.putValue(SHORT_DESCRIPTION, "Draw in red");
     greenAction.putValue(SHORT_DESCRIPTION, "Draw in green");
     blueAction.putValue(SHORT_DESCRIPTION, "Draw in blue");
     yellowAction.putValue(SHORT_DESCRIPTION, "Draw in yellow");
   }

   // Create the Color menu
   private void createColorMenu() {
     createElementColorActions();
     colorMenu = new JMenu("Color");                                     // Create Elements menu
     colorMenu.setMnemonic('C');                                         // Create shortcut
     createRadioButtonDropDown(colorMenu, colorActions, blueAction);
     menuBar.add(colorMenu);                                             // Add the color menu
   }

   // Menu creation helper
   private void createRadioButtonDropDown(JMenu menu, Action[] actions, Action selected) {
     ButtonGroup group = new ButtonGroup();
     JRadioButtonMenuItem item = null;
     for(Action action : actions) {
       group.add(menu.add(item = new JRadioButtonMenuItem(action)));
       if(action == selected) {
         item.setSelected(true);                                         // This is default selected
       }
     }
   }

   // Create pop-up menu
   private void createPopupMenu() {
     // Element menu items
     popup.add(new JMenuItem(lineAction));
     popup.add(new JMenuItem(rectangleAction));
     popup.add(new JMenuItem(circleAction));
     popup.add(new JMenuItem(curveAction));
     popup.add(new JMenuItem(textAction));

     popup.addSeparator();

     // Color menu items
     popup.add(new JMenuItem(redAction));
     popup.add(new JMenuItem(yellowAction));
     popup.add(new JMenuItem(greenAction));
     popup.add(new JMenuItem(blueAction));
   }

   // Create toolbar buttons on the toolbar
   private void createToolbar() {
     for(FileAction action: fileActions){
       if(action != exitAction && action != closeAction)
         addToolbarButton(action);                                       // Add the toolbar button
     }
     toolBar.addSeparator();

     // Create Color menu buttons
     for(ColorAction action:colorActions){
         addToolbarButton(action);                                       // Add the toolbar button
     }

     toolBar.addSeparator();

     // Create Elements menu buttons
     for(TypeAction action:typeActions){
         addToolbarButton(action);                                       // Add the toolbar button
     }
  }

   // Create and add a toolbar button
   private void addToolbarButton(Action action) {
     JButton button = new JButton(action);                               // Create from Action
     button.setBorder(BorderFactory.createCompoundBorder(                // Add button border
            new EmptyBorder(2,5,5,2),                                    // Outside border
            BorderFactory.createRaisedBevelBorder()));                   // Inside border
     button.setHideActionText(true);                                     // No label on the button
     toolBar.add(button);                                                // Add the toolbar button
   }

   // Return the current drawing color
   public Color getElementColor() {
     return elementColor;
   }

   // Return the current element type
   public int getElementType() {
     return elementType;
   }

   // Return current text font
   public Font getFont() {
     return textFont;
   }

   // Method to set the current font
   public void setFont(Font font) {
     textFont = font;
   }

   // Retrieve the pop-up menu
   public JPopupMenu getPopup() {
     return popup;
   }

   // Set radio button menu checks
   private void setChecks(JMenu menu, Object eventSource) {
     if(eventSource instanceof JButton){
       JButton button = (JButton)eventSource;
       Action action = button.getAction();
       for(int i = 0 ; i<menu.getItemCount() ; ++i) {
         JMenuItem item = menu.getItem(i);
         item.setSelected(item.getAction() == action);
       }
     }
   }

   // Handle About menu events
   public void actionPerformed(ActionEvent e)  {
     if(e.getSource() == aboutItem) {
       // Create about dialog with the app window as parent
       JOptionPane.showMessageDialog(this,                               // Parent
                        "Sketcher Copyright Ivor Horton 2011",           // Message
                        "About Sketcher",                                // Title
                        JOptionPane.INFORMATION_MESSAGE);                // Message type
     } else if(e.getSource() == fontItem) {                              // Set the dialog window position
       fontDlg.setLocationRelativeTo(this);
       fontDlg.setVisible(true);                                         // Show the dialog
     }
   }

   // Inner class defining Action objects for File menu items
   class FileAction extends AbstractAction {
     // Create action with a name
     FileAction(String name) {
       super(name);
     }

     // Create action with a name and accelerator
     FileAction(String name, char ch, int modifiers) {
       super(name);
       putValue(ACCELERATOR_KEY, KeyStroke.getKeyStroke(ch, modifiers));

       // Now find the character to underline
       int index = name.toUpperCase().indexOf(ch);
       if(index != -1) {
         putValue(DISPLAYED_MNEMONIC_INDEX_KEY, index);
       }
     }

     // Event handler
     public void actionPerformed(ActionEvent e) {
       // You will add action code here eventually...
     }
   }

   // Inner class defining Action objects for Element type menu items
   class TypeAction extends AbstractAction {
     // Create action with just a name property
     TypeAction(String name, int typeID) {
       super(name);
       this.typeID = typeID;
     }

     // Create action with a name and an accelerator
     private TypeAction(String name,int typeID, char ch, int modifiers) {
       this(name, typeID);
       putValue(ACCELERATOR_KEY, KeyStroke.getKeyStroke(ch, modifiers));

       // Now find the character to underline
       int index = name.toUpperCase().indexOf(ch);
       if(index != -1) {
         putValue(DISPLAYED_MNEMONIC_INDEX_KEY, index);
       }
     }

     public void actionPerformed(ActionEvent e) {
       elementType = typeID;
       setChecks(elementMenu, e.getSource());
       statusBar.setTypePane(typeID);
     }

     private int typeID;
   }

   // Handles color menu items
   class ColorAction  extends AbstractAction {
     // Create an action with a name and a color
     public ColorAction(String name, Color color) {
       super(name);
       this.color = color;
     }

     // Create an action with a name, a color, and an accelerator
     public ColorAction(String name, Color color, char ch, int modifiers) {
       this(name, color);
       putValue(ACCELERATOR_KEY, KeyStroke.getKeyStroke(ch, modifiers));

       // Now find the character to underline
       int index = name.toUpperCase().indexOf(ch);
       if(index != -1) {
         putValue(DISPLAYED_MNEMONIC_INDEX_KEY, index);
       }
     }

     public void actionPerformed(ActionEvent e) {
       elementColor = color;
       setChecks(colorMenu, e.getSource());
       statusBar.setColorPane(color);
     }

     private Color color;
   }

   // File actions
   private FileAction newAction, openAction, closeAction, saveAction, saveAsAction, printAction, exitAction;
   private FileAction[] fileActions;                                     // File actions as an array

   // Element type actions
   private TypeAction lineAction, rectangleAction, circleAction, curveAction, textAction;
   private TypeAction[] typeActions;                                     // Type actions as an array

 // Element color actions
   private ColorAction redAction, yellowAction,greenAction, blueAction;
   private ColorAction[] colorActions;                                   // Color actions as an array

   private JMenuBar menuBar = new JMenuBar();                            // Window menu bar
   private JMenu elementMenu;                                            // Elements menu
   private JMenu colorMenu;                                              // Color menu
   private JMenu optionsMenu;                                            // Options menu

   private StatusBar statusBar = new StatusBar();                        // Window status bar
   private FontDialog fontDlg;                                           // The font dialog

   private JMenuItem aboutItem;                                          // About menu item
   private JMenuItem fontItem;                                           // Font chooser menu item

   private JPopupMenu popup = new JPopupMenu("General");                 // Window pop-up
   private Color elementColor = DEFAULT_ELEMENT_COLOR;                   // Current element color
   private int elementType = DEFAULT_ELEMENT_TYPE;                       // Current element type
   private Font textFont = DEFAULT_FONT;                                 // Default font for text elements
   private JToolBar toolBar = new JToolBar();                            // Window toolbar
   private Sketcher theApp;                                              // The application object
 }