Java基础之处理事件——添加工具提示（Sketcher 9 with tooltips）

控制台程序。

在Java中实现对工具提示的支持是非常简单的，秘诀仍在我们一直使用的Action对象中。Action对象拥有存储工具提示文本的内置功能因为文本是通过SHORT_DESCRIPTION键提供的，我们只需要把工具提示文本存储为这个键的值即可。

下面仅列出修改后的SketcherFrame类：

 // 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 {
   // Constructor
   public SketcherFrame(String title) {
     setTitle(title);                                                   // Set the window title
     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
     createToolbar();
     toolBar.setRollover(true);
     getContentPane().add(toolBar, BorderLayout.NORTH);
   }

   // 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);

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

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

     // 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");
   }

   // 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");
     blueAction.putValue(SHORT_DESCRIPTION, "Draw in blue");
     greenAction.putValue(SHORT_DESCRIPTION, "Draw in green");
     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 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
   }

   // 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);
       }
     }
   }

   // 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());
     }

     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());
     }

     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;
   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 Color elementColor = DEFAULT_ELEMENT_COLOR;                  // Current element color
   private int elementType = DEFAULT_ELEMENT_TYPE;                      // Current element type
   private JToolBar toolBar = new JToolBar();                           // Window toolbar
 }