swing GeneralPath::cubicTo绘制平滑曲线

 
      
 import javax.swing.*; 
      
 
      
 import java.awt.*; 
      
 
      
 import java.awt.geom.GeneralPath; 
      
 
      
 
      
 public class DrawSmoothCurve extends JPanel { 
      
 
      
 private Point[] points = { 
      
 
      
 new Point( 0, 0), 
      
 
      
 new Point( 100, 100), 
      
 
      
 new Point( 200, - 100), 
      
 
      
 new Point( 300, 100), 
      
 
      
 new Point( 330, - 80), 
      
 
      
 new Point( 350, - 70) 
      
 
      

        }; 
      
 
      
 
      

        GeneralPath path = new GeneralPath(); 
      
 
      
 
      
 public DrawSmoothCurve() { 
      
 
      

        path.moveTo(points[ 0].x, points[ 0].y); 
      
 
      
 
      
 for ( int i = 0; i < points.length- 1; ++i) { 
      
 
      

        Point sp = points[i]; 
      
 
      

        Point ep = points[i+ 1]; 
      
 
      

        Point c1 = new Point((sp.x + ep.x)/ 2, sp.y); 
      
 
      

        Point c2 = new Point((sp.x + ep.x)/ 2, ep.y); 
      
 
      
 
      

        path.curveTo(c1.x, c1.y, c2.x, c2.y, ep.x, ep.y); 
      
 
      

        } 
      
 
      

        } 
      
 
      
 
      
 @Override 
      
 
      
 protected void paintComponent(Graphics g) { 
      
 
      
 super.paintComponent(g); 
      
 
      
 
      

        Graphics2D g2d = (Graphics2D) g; 
      
 
      

        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON); 
      
 
      

        g2d.setStroke( new BasicStroke( 2)); 
      
 
      

        g2d.translate( 40, 130); 
      
 
      

        g2d.draw(path); 
      
 
      
 
      
 for ( int i = 0; i < points.length; ++i) { 
      
 
      

        g2d.setColor(Color.GRAY); 
      
 
      

        g2d.fillOval(points[i].x- 4, points[i].y- 4, 8, 8); 
      
 
      

        g2d.setColor(Color.BLACK); 
      
 
      

        g2d.drawOval(points[i].x- 4, points[i].y- 4, 8, 8); 
      
 
      

        } 
      
 
      

        } 
      
 
      
 
      
 private static void createAndShowGui() { 
      
 
      

        JFrame frame = new JFrame( "Smooth Curve"); 
      
 
      

        frame.setContentPane( new DrawSmoothCurve()); 
      
 
      

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
      
 
      

        frame.setSize( 420, 280); 
      
 
      

        frame.setLocationRelativeTo( null); 
      
 
      

        frame.setVisible( true); 
      
 
      

        } 
      
 
      
 
      
 public static void main(String[] args) { 
      
 
      

        SwingUtilities.invokeLater( new Runnable() { 
      
 
      
 public void run() { 
      
 
      

        createAndShowGui(); 
      
 
      

        } 
      
 
      

        }); 
      
 
      

        } 
      
 
      

        }