此程序的运行效果图：</td> <td width="244" valign="top" class="ArticleTeitle">
import java.awt.*; import java.awt.geom.*; import javax.swing.*; import javax.swing.plaf.basic.*; import javax.swing.plaf.*; import javax.swing.border.*; public class EllipseButton extends JButton { // Constructor - only support this version for demo public EllipseButton(String text) { super(text); // Create the private UI for the component. The UI // is a delegate object that handles paint requests for // the component. this.setUI(EllipseButtonUI.createUI(this)); // Get rid of the rectangular button border this.setBorder(null); // Set this so the background of the ellipse will not // be filled in with the background color this.setContentAreaFilled(false); // Add a nice chunky margin to give room for the ellipse this.setMargin(new Insets(8, 14, 8, 14)); } // Test frame for our button public static void main(String [] args) { // Put a bigger button font in the UIManager UIManager.put("Button.font", new Font("Arial", 0, 20)); // Create a frame and add the button JFrame frame = new JFrame(); frame.setLocation(100, 100); frame.setSize(200, 80); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setTitle("Elliptical Button"); frame.getContentPane().setLayout(new GridBagLayout()); EllipseButton button = new EllipseButton("Elliptical"); frame.getContentPane().add(button); // Set the background to a tasteful color and show the frame frame.getContentPane().setBackground(new Color(230, 230, 150)); frame.setVisible(true); } } // This UI delegate is extended from the basic button UI that is // the base class for all button UI delegates in all PLAFs. class EllipseButtonUI extends BasicButtonUI { // Create a singleton instance to share among all instances // of. protected static EllipseButtonUI singleton = new EllipseButtonUI(); protected static Stroke thickStroke = new BasicStroke(2.0f); // Return the singleton instance for all component instances public static ComponentUI createUI(JComponent c) { return singleton; } public void paint(Graphics g, JComponent c) { Graphics2D g2 = (Graphics2D) g; g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON); // Get the button's area from the component // reference. AbstractButton b = (AbstractButton) c; Rectangle viewRect = new Rectangle(); viewRect.x = 0; viewRect.y = 0; viewRect.width = b.getWidth() - 1; viewRect.height = b.getHeight() - 1; // Shrink everything by a pixel so the extra pixels created // by anti-aliasing will fit viewRect.grow(-2, -2); // Create a Java2D ellipse shape that is bounded by // the button's visible rectangle Ellipse2D ellipse = new Ellipse2D.Float(); ellipse.setFrame(viewRect.getX(), viewRect.getY(), viewRect.getWidth(), viewRect.getHeight()); ButtonModel model = b.getModel(); boolean pressed = (model.isArmed() && model.isPressed()) || model.isSelected(); pressed = !pressed; if (pressed) { Color background = UIManager.getColor("Button.select"); g2.setPaint(background == null ? Color.gray : background); } else g2.setPaint(UIManager.getColor("control")); // Fill the ellipse with the background color g2.fill(ellipse); Arc2D arc = new Arc2D.Float(); arc.setFrame(viewRect.getX(), viewRect.getY(), viewRect.getWidth(), viewRect.getHeight()); arc.setArcType(Arc2D.OPEN); // To draw the highlights diagonally, use this method // to set the start and end of the arc to be the upper // right and lower left of the bounding rectangle. arc.setAngles(viewRect.getWidth(), 0, 0, viewRect.getHeight()); // Set the stroke to draw a thick line g2.setStroke(thickStroke); // Paint the upper left side of the arc. If the button // is pressed, paint it with shadow, otherwise paint with // highlight g2.setPaint(pressed ? UIManager.getColor("controlDkShadow") : UIManager.getColor("controlHighlight")); g2.draw(arc); // Flip the angles so the arc represents the other // portion of the ellipse. Paint the lower right side of // the arc. If the button is pressed, paint it with // highlight, otherwise paint with shadow. arc.setAngles(0, viewRect.getHeight(), viewRect.getWidth(), 0); g2.setPaint(pressed ? UIManager.getColor("controlHighlight") : UIManager.getColor("controlShadow")); g2.draw(arc); super.paint(g, c); // To be a good citizen, change the rendering hints // of the graphic context back to the default. g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_OFF); } // Return the 'preferred' size of the component based on the // size of the text. Cheat a little by calling the // superclass and tacking on enough extra space to ensure // there is sufficient room for the elliptical border. public Dimension getPreferredSize(JComponent c) { // Call the superclass AbstractButton b = (AbstractButton) c; Dimension dim = super.getPreferredSize(c); // Increment the preferred height and width by the // size of the margin dim.height += (b.getMargin().top + b.getMargin().bottom); dim.width += (b.getMargin().left + b.getMargin().right); return dim; } }
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