12.16 Displaying Graphics Examples

Example 12-20 shows the GraphicsExampleFrame class we've been using to display GraphicsExample implementations throughout this chapter. This program mainly demonstrates the Swing and Printing APIs, but is included here for completeness. The paintComponent( ) method of the GraphicsExamplePane inner class is where the draw( ) method of each GraphicsExample object is invoked. Although paintComponent( ) is declared as taking a Graphics object, in Java 1.2 and later it is always passed a Graphics2D object, which can be safely cast to that type.

Example 12-20. GraphicsExampleFrame.java

package je3.graphics; import java.awt.*; import java.awt.event.*; import javax.swing.*; import javax.swing.event.*; import java.awt.print.*; /**  * This class displays one or more GraphicsExample objects in a  * Swing JFrame and a JTabbedPane  */ public class GraphicsExampleFrame extends JFrame {     public GraphicsExampleFrame(final GraphicsExample[  ] examples) {         super("GraphicsExampleFrame");         Container cpane = getContentPane( );   // Set up the frame          cpane.setLayout(new BorderLayout( ));         final JTabbedPane tpane = new JTabbedPane( ); // And the tabbed pane          cpane.add(tpane, BorderLayout.CENTER);         // Add a menubar         JMenuBar menubar = new JMenuBar( );         // Create the menubar         this.setJMenuBar(menubar);                 // Add it to the frame         JMenu filemenu = new JMenu("File");        // Create a File menu         menubar.add(filemenu);                     // Add to the menubar         JMenuItem print = new JMenuItem("Print");  // Create a Print item         filemenu.add(print);                       // Add it to the menu         JMenuItem quit = new JMenuItem("Quit");    // Create a Quit item         filemenu.add(quit);                        // Add it to the menu         // Tell the Print menu item what to do when selected         print.addActionListener(new ActionListener( ) {                 public void actionPerformed(ActionEvent e) {                     // Get the currently displayed example, and call                      // the print method (defined below)                     print(examples[tpane.getSelectedIndex( )]);                 }             });         // Tell the Quit menu item what to do when selected         quit.addActionListener(new ActionListener( ) {                 public void actionPerformed(ActionEvent e) { System.exit(0); }             });         // In addition to the Quit menu item, also handle window close events         this.addWindowListener(new WindowAdapter( ) {                 public void windowClosing(WindowEvent e) { System.exit(0); }             });         // Insert each of the example objects into the tabbed pane         for(int i = 0; i < examples.length; i++) {             GraphicsExample e = examples[i];             tpane.addTab(e.getName( ), new GraphicsExamplePane(e));         }     }     /**      * This inner class is a custom Swing component that displays      * a GraphicsExample object.      */     public class GraphicsExamplePane extends JComponent {         GraphicsExample example;  // The example to display         Dimension size;           // How much space it requires                  public GraphicsExamplePane(GraphicsExample example) {             this.example = example;             size = new Dimension(example.getWidth( ), example.getHeight( ));         }         /** Draw the component and the example it contains */         public void paintComponent(Graphics g) {             g.setColor(Color.white);                    // set the background             g.fillRect(0, 0, size.width, size.height);  // to white             g.setColor(Color.black);             // set a default drawing color             example.draw((Graphics2D) g, this);  // ask example to draw itself         }         // These methods specify how big the component must be         public Dimension getPreferredSize( ) { return size; }         public Dimension getMinimumSize( ) { return size; }     }     /** This method is invoked by the Print menu item */     public void print(final GraphicsExample example) {         // Start off by getting a printer job to do the printing         PrinterJob job = PrinterJob.getPrinterJob( );         // Wrap the example in a Printable object (defined below)         // and tell the PrinterJob that we want to print it         job.setPrintable(new PrintableExample(example));         // Display the print dialog to the user         if (job.printDialog( )) {             // If they didn't cancel it, then tell the job to start printing             try {                 job.print( );             }             catch(PrinterException e) {                 System.out.println("Couldn't print: " + e.getMessage( ));             }         }     }     /**      * This inner class implements the Printable interface in order to print      * a GraphicsExample object.      **/     class PrintableExample implements Printable  {         GraphicsExample example;  // The example to print         // The constructor.  Just remember the example         public PrintableExample(GraphicsExample example) {             this.example = example;         }         /**          * This method is called by the PrinterJob to print the example          **/         public int print(Graphics g, PageFormat pf, int pageIndex) {             // Tell the PrinterJob that there is only one page             if (pageIndex != 0) return NO_SUCH_PAGE;             // The PrinterJob supplies us a Graphics object to draw with.             // Anything drawn with this object will be sent to the printer.             // The Graphics object can safely be cast to a Graphics2D object.             Graphics2D g2 = (Graphics2D)g;             // Translate to skip the left and top margins.             g2.translate(pf.getImageableX( ), pf.getImageableY( ));             // Figure out how big the printable area is, and how big             // the example is.             double pageWidth = pf.getImageableWidth( );             double pageHeight = pf.getImageableHeight( );             double exampleWidth = example.getWidth( );             double exampleHeight = example.getHeight( );             // Scale the example if needed             double scalex = 1.0, scaley = 1.0;             if (exampleWidth > pageWidth) scalex = pageWidth/exampleWidth;             if (exampleHeight > pageHeight) scaley = pageHeight/exampleHeight;             double scalefactor = Math.min(scalex, scaley);             if (scalefactor != 1) g2.scale(scalefactor, scalefactor);             // Finally, call the draw( ) method of the example, passing in             // the Graphics2D object for the printer             example.draw(g2, GraphicsExampleFrame.this);             // Tell the PrinterJob that we successfully printed the page             return PAGE_EXISTS;         }     }     /**       * The main program.  Use Java reflection to load and instantiate      * the specified GraphicsExample classes, then create a      * GraphicsExampleFrame to display them.      **/     public static void main(String[  ] args) {         GraphicsExample[  ] examples = new GraphicsExample[args.length];         // Loop through the command line arguments         for(int i=0; i < args.length; i++) {             // The class name of the requested example             String classname = args[i];                          // If no package is specified, assume it is in this package             if (classname.indexOf('.') == -1)                 classname = "je3.graphics." + args[i];             // Try to instantiate the named GraphicsExample class             try {                 Class exampleClass = Class.forName(classname);                 examples[i] = (GraphicsExample) exampleClass.newInstance( );             }             catch (ClassNotFoundException e) {  // unknown class                 System.err.println("Couldn't find example: "  + classname);                 System.exit(1);             }             catch (ClassCastException e) {      // wrong type of class                 System.err.println("Class " + classname +                                     " is not a GraphicsExample");                 System.exit(1);             }             catch (Exception e) {  // class doesn't have a public constructor                 // catch InstantiationException, IllegalAccessException                 System.err.println("Couldn't instantiate example: " +                                    classname);                 System.exit(1);             }         }         // Now create a window to display the examples in, and make it visible         GraphicsExampleFrame f = new GraphicsExampleFrame(examples);         f.pack( );         f.setVisible(true);     } }