transparencyexample.java

源代码使用说明 本书全部代码全部在JDK中调试成功

import javax.swing.*;
import java.awt.*;
import java.awt.geom.*;

/** An illustration of the use of AlphaComposite to make partially
 *  transparent drawings. 
 */

public class TransparencyExample extends JPanel {
  private static int gap=10, width=60, offset=20,
                     deltaX=gap+width+offset;
  private Rectangle
    blueSquare = new Rectangle(gap+offset, gap+offset, width, width),
    redSquare = new Rectangle(gap, gap, width, width);

  private AlphaComposite makeComposite(float alpha) {
    int type = AlphaComposite.SRC_OVER;
    return(AlphaComposite.getInstance(type, alpha));
  }

  private void drawSquares(Graphics2D g2d, float alpha) {
    Composite originalComposite = g2d.getComposite();
    g2d.setPaint(Color.blue);
    g2d.fill(blueSquare);
    g2d.setComposite(makeComposite(alpha));
    g2d.setPaint(Color.red);
    g2d.fill(redSquare);
    g2d.setComposite(originalComposite);
  }

  public void paintComponent(Graphics g) {
    super.paintComponent(g);
    Graphics2D g2d = (Graphics2D)g;
    for(int i=0; i<11; i++) {
      drawSquares(g2d, i*0.1F);
      g2d.translate(deltaX, 0);
    }
  }

  public static void main(String[] args) {
    String title = "Transparency example: alpha of the top (red) " +
                   "square ranges from 0.0 at the left to 1.0 at " +
                   "the right. Bottom (blue) square is opaque.";
    WindowUtilities.openInJFrame(new TransparencyExample(),
                                 11*deltaX + 2*gap, deltaX + 3*gap,
                                 title, Color.lightGray);
  }
}