Java 绘制环形的文字 (Circle Text Demo)详解编程语言

CircleTextDemo.java

import java.awt.*; 
import java.awt.event.*; 
import java.awt.geom.*; 
 
/** 
 * A demo class that illustrates drawing text 
 * along the outside of a circle. 
 */ 
public class CircleTextDemo extends Canvas { 
    Frame myframe; 
    TextField text; 
    Button printBtn; 
    Font myfont; 
    Color textcolor; 
    Color circlecolor; 
 
    /** 
     * Create a CircleTextDemo canvas and frame 
     * with default settings. 
     */ 
    public CircleTextDemo() { 
        this("Serif", Font.PLAIN, 18, Color.pink, Color.black); 
    } 
 
    /** 
     * Create a CircleTextDemo canvas and frame 
     * with supplied settings. 
     * 
     * @param ff Font family (usually "Serif") 
     * @param fs Font style (usually Font.PLAIN) 
     * @param fz Font size (usually 18) 
     * @param bg Background color for this canvas (usually pink) 
     * @param fg Foreground color for text (usually black) 
     */ 
    public CircleTextDemo(String ff, int fs, int fz, Color bg, Color fg) { 
        setBackground(bg); 
        circlecolor = bg.brighter(); 
        textcolor = fg; 
        myfont = new Font(ff, fs, fz); 
 
        text = new TextField("Text on a circle using Java 2D Graphics!"); 
        myframe = new Frame("CircleTextDemo"); 
   printBtn = new Button("Print"); 
        myframe.add(text, BorderLayout.NORTH); 
        myframe.add(this, BorderLayout.CENTER); 
   myframe.add(printBtn, BorderLayout.SOUTH); 
        myframe.setSize(new Dimension(300,340)); 
        myframe.setLocation(150,140); 
        myframe.addWindowListener(new WindowAdapter() { 
                public void windowClosing(WindowEvent we) { 
                    System.exit(0); 
                } 
            }); 
        text.addActionListener(new ActionListener() { 
                public void actionPerformed(ActionEvent ae) { 
                    repaint(); 
                } 
            }); 
   printBtn.addActionListener(new FramePrinter(myframe)); 
        myframe.setVisible(true); 
    } 
 
    /** 
     * Paint the contents of the CircleDemoText canvas. 
     * 
     * @param g - a Graphics, hopefully a Graphics2D 
     */ 
    public void paint(Graphics g) { 
        String st = text.getText(); 
        if (st.length() == 0) return; 
        if (g instanceof Graphics2D) { 
            Dimension cd = getSize(); 
            Point pt = new Point(cd.width / 2, cd.height / 2); 
            int radius = (int)(pt.x * 0.84); 
            g.setColor(circlecolor); 
            g.drawArc(pt.x - radius, pt.y - radius, 
                      radius*2-1, radius*2-1, 
                      0, 360); 
            g.setColor(textcolor); 
            g.setFont(myfont); 
            drawCircleText((Graphics2D)g, st, pt, radius, -Math.PI/2, 1.0); 
        } 
        else { 
            System.out.println("Cannot draw curved text without a Graphics2D"); 
        } 
    } 
 
    /** 
     * Draw a piece of text on a circular curve, one 
     * character at a time.  This is harder than it looks... 
     * 
     * This method accepts many arguments: 
     *   g - a Graphics2D ready to be used to draw, 
     *   st - the string to draw, 
     *   center - the center point of the circle (Point), 
     *   r - the radius of the circle, 
     *   a1 - the beginning angle on the circle to start, in radians, 
     *   af - the angle advance factor (usually 1.0) 
     */ 
    static void drawCircleText(Graphics2D g, String st, Point center, 
                               double r, double a1, double af) 
    { 
        double curangle = a1; 
   double curangleSin; 
        Point2D c = new Point2D.Double(center.x, center.y); 
        char ch[] = st.toCharArray(); 
        FontMetrics fm = g.getFontMetrics(); 
        AffineTransform xform1, cxform; 
        xform1 = AffineTransform.getTranslateInstance(c.getX(),c.getY()); 
        for(int i = 0; i < ch.length; i++) { 
            double cwid = (double)(getWidth(ch[i],fm)); 
            if (!(ch[i] == ' ' || Character.isSpaceChar(ch[i]))) { 
                cwid = (double)(fm.charWidth(ch[i])); 
                cxform = new AffineTransform(xform1); 
                cxform.rotate(curangle, 0.0, 0.0); 
                String chstr = new String(ch, i, 1); 
                g.setTransform(cxform); 
                g.drawString(chstr, (float)(-cwid/2), (float)(-r)); 
            } 
 
            // compute advance of angle assuming cwid<<radius 
            if (i < (ch.length - 1)) { 
                double adv = cwid/2.0 + fm.getLeading() + getWidth(ch[i + 1],fm)/2.0; 
      // Use of atan() suggested by Michael Moradzadeh 
                curangle += Math.atan(adv / r); 
      // Original code was: 
      // curangle += Math.sin(adv / r); 
 
            } 
        } 
    } 
 
    /** 
     * Get the width of a given character under the 
     * specified FontMetrics, interpreting all spaces as 
     * en-spaces. 
     */ 
    static int getWidth(char c, FontMetrics fm) { 
        if (c == ' ' || Character.isSpaceChar(c)) { 
            return fm.charWidth('n'); 
        } 
        else { 
            return fm.charWidth(c); 
        } 
    } 
 
    public static void main(String args[]) { 
        CircleTextDemo ctd; 
        ctd = new CircleTextDemo(); 
    } 
 
    class FramePrinter implements ActionListener { 
   private Frame fr; 
   public FramePrinter(Frame f) { fr = f; } 
   public void actionPerformed(ActionEvent ae) { 
       PrintJob pjob; 
       pjob = fr.getToolkit().getPrintJob(fr, 
          "Printing Circle Demo", null, null); 
       if (pjob != null) { 
      Graphics g = pjob.getGraphics(); 
      if (g != null) { 
          g.translate(100,100); 
          fr.printAll(g); 
          g.dispose(); 
      } 
      pjob.end(); 
       } 
   } 
    } 
 
}