arrowicon.java

这是一个英文版的《Java程序设计与问题解决》现在好多大学都当成教材

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

public class ArrowIcon implements Icon, SwingConstants {
    private int width = 9;
    private int height = 18;

    private int[] xPoints = new int[4];
    private int[] yPoints = new int[4];

    public ArrowIcon(int direction) {
        if (direction == LEFT) {
            xPoints[0] = width;
            yPoints[0] = -1;
            xPoints[1] = width;
            yPoints[1] = height;
            xPoints[2] = 0;
            yPoints[2] = height/2;
            xPoints[3] = 0;
            yPoints[3] = height/2 - 1;
        } else /* direction == RIGHT */ {
            xPoints[0] = 0;
            yPoints[0] = -1;
            xPoints[1] = 0;
            yPoints[1] = height;
            xPoints[2] = width;
            yPoints[2] = height/2;
            xPoints[3] = width;
            yPoints[3] = height/2 - 1;
        }
    }

    public int getIconHeight() {
        return height;
    }

    public int getIconWidth() {
        return width;
    }

    public void paintIcon(Component c, Graphics g, int x, int y) {
        int length = xPoints.length;
        int adjustedXPoints[] = new int[length];
        int adjustedYPoints[] = new int[length];

        for (int i = 0; i < length; i++) {
            adjustedXPoints[i] = xPoints[i] + x;
            adjustedYPoints[i] = yPoints[i] + y;
        }

        if (c.isEnabled()) {
            g.setColor(Color.black);
        } else {
            g.setColor(Color.gray);
        }

        g.fillPolygon(adjustedXPoints, adjustedYPoints, length);
    }
}