AbstractDisplay.java

/* 
 * AP(r) Computer Science GridWorld Case Study:
 * Copyright(c) 2002-2006 College Entrance Examination Board 
 * (http://www.collegeboard.com).
 *
 * This code is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * @author Julie Zelenski
 * @author Cay Horstmann
 */

package info.gridworld.gui;

import java.awt.Rectangle;
import java.beans.*;
import java.lang.reflect.*;
import java.awt.Component;
import java.awt.Graphics2D;
import java.awt.BasicStroke;

/**
 * This class provides common implementation code for drawing objects. It will
 * translate, scale, and rotate the graphics system as needed and then invoke
 * its abstract <code>draw</code> method. Subclasses of this abstract class
 * define <code>draw</code> to display an object in a fixed size and
 * orientation. <br />
 * This code is not tested on the AP CS A and AB exams. It contains GUI
 * implementation details that are not intended to be understood by AP CS
 * students.
 */

public abstract class AbstractDisplay implements Display
{
    /**
     * Draw the given object. Subclasses should implement this method to draw
     * the occupant facing North in a cell of size (1,1) centered around (0,0) on
     * the drawing surface. (All scaling/rotating has been done beforehand).
     * @param obj the occupant we want to draw
     * @param comp the component on which to draw
     * @param g2 the graphics context
     */
    abstract public void draw(Object obj, Component comp, Graphics2D g2);

    /**
     * Draw the given object. Scales and rotates the coordinate appropriately
     * then invokes the simple draw method above that is only responsible for
     * drawing a unit-length occupant facing North.
     * @param obj the occupant we want to draw
     * @param comp the component on which to draw
     * @param g2 the graphics context
     * @param rect rectangle in which to draw
     */
    public void draw(Object obj, Component comp, Graphics2D g2, Rectangle rect)
    {
        float scaleFactor = Math.min(rect.width, rect.height);
        g2 = (Graphics2D) g2.create();

        // Translate to center of the object
        g2.translate(rect.x + rect.width / 2.0, rect.y + rect.height / 2.0);

        // Rotate drawing surface before drawing to capture object's
        // orientation (direction).
        if (obj != null)
        {
            Integer direction = (Integer) getProperty(obj, "direction");
            int rotationInDegrees = direction == null ? 0 : direction
                    .intValue();
            g2.rotate(Math.toRadians(rotationInDegrees));
        }
        // Scale to size of rectangle, adjust stroke back to 1-pixel wide
        g2.scale(scaleFactor, scaleFactor);
        g2.setStroke(new BasicStroke(1.0f / scaleFactor));
        draw(obj, comp, g2);
    }

    public static Object getProperty(Object obj, String propertyName)
    {
        if (obj == null)
            return null;
        try
        {
            BeanInfo info = Introspector.getBeanInfo(obj.getClass());
            PropertyDescriptor[] descriptors = info.getPropertyDescriptors();
            for (int i = 0; i < descriptors.length; i++)
            {
                if (descriptors[i].getName().equals(propertyName))
                {
                    Method getter = descriptors[i].getReadMethod();
                    if (getter == null)
                        return null;
                    try {
                    return getter.invoke(obj);
                    } catch (Exception ex) {
                        System.out.println(descriptors[i].getName());
                        return null;
                    }
                }
            }
        }
        catch (Exception ex)
        {
            ex.printStackTrace();
        }
        return null;
    }
}