Computer Science 120
Introduction to Programming

Spring 2012, Siena College

Home     Syllabus     Teresco Schedule     Small Schedule     Examples

DragStudentsS12 Demo

A working demo of DragStudentsS12 will appear below. Click inside the applet to interact with it.

DragStudentsS12 BlueJ Project

Click here to download a BlueJ project for DragStudentsS12.

DragStudentsS12 Source Code

The Java source code for DragStudentsS12 is below. Click on a file name to download it.

DragStudentsS12.java

import objectdraw.*;
import java.awt.*;

/*
 * Example DragStudents: randomly scatter draggable student pictures on the canvas
 *
 * Jim Teresco, Siena College, CSIS 120, Spring 2011
 *
 * $Id: DragStudentsS12.java 1846 2012-04-10 15:29:49Z terescoj $
 */

public class DragStudentsS12 extends WindowController {

    // all images will be resized to this
    private static final int IMAGE_SIZE = 50;
    // the array of image file names
    private String[] imageFiles = {
            "amandameher-head.jpg",
            "amarmian-head.jpg",
            "annagrant-head.jpg",
            "corydelagorgendiere-head.jpg",
            "emilymejia-head.jpg",
            "jamessaddlemire-head.jpg",
            "johnbestafka-head.jpg",
            "johnkiernozek-head.jpg",
            "joshmcdonald-head.jpg",
            "juliannesgoifo-head.jpg",
            "justinrose-head.jpg",
            "kathleenrotondo-head.jpg",
            "kathrynmannix-head.jpg",
            "laurendavis-head.jpg",
            "lesliakeo-head.jpg",
            "marissabianchi-head.jpg",
            "maryritchie-head.jpg",
            "micaelaethier-head.jpg",
            "rachelstoklosa-head.jpg",
            "ryanclancy-head.jpg",
            "shannonmuldowney-head.jpg",
            "tylerkallquist-head.jpg"
        };

    // array of VisibleImage objects for display and dragging
    private VisibleImage[] heads;

    // support for dragging
    private boolean dragging;
    private VisibleImage selectedHead;
    private Location lastPoint;

    // how much to scale up images when dragging
    private static final int DRAG_ZOOM = 4;

    /**
     * draw the initial random scattering of student pictures
     * on the canvas, taking care not to overlap initially.
     */
    public void begin() {

        // generators for legal positions with the images completely on the canvas
        RandomIntGenerator xPosGen = new RandomIntGenerator(0, canvas.getWidth() - IMAGE_SIZE);
        RandomIntGenerator yPosGen = new RandomIntGenerator(0, canvas.getHeight() - IMAGE_SIZE);

        heads = new VisibleImage[imageFiles.length];

        // place the images
        for (int imageNum = 0; imageNum < heads.length; imageNum++) {
            heads[imageNum] = new VisibleImage(getImage(imageFiles[imageNum]),
                xPosGen.nextValue(),
                yPosGen.nextValue(),
                canvas);
            heads[imageNum].setWidth(IMAGE_SIZE);
            heads[imageNum].setHeight(IMAGE_SIZE);

            // move this image around until we find a position where it
            // does not overlap with any already-placed image
            while (overlapsAny(imageNum)) {
                heads[imageNum].moveTo(xPosGen.nextValue(), yPosGen.nextValue());
            }
        }

        // setup for dragging
        dragging = false;
        selectedHead = heads[0];
    }

    /**
     * a private helper method to determine whether the VisibleImage
     * at heads[index] overlaps with any of the VisibleImages at 
     * heads[0] up through heads[index-1].
     * 
     * @param index the index of the VisibleImage to check for overlap
     * @return a boolean indicating whether heads[index] overlaps any of
     *  heads[0] through heads[index-1]
     */
    private boolean overlapsAny(int index) {

        // check each possible overlap
        for (int compareTo = 0; compareTo < index; compareTo++) {
            if (heads[index].overlaps(heads[compareTo])) {
                return true;
            }
        }

        // we didn't find any overlap, so we return false
        return false;
    }

    /**
     * start dragging if the Location is on one of the student images
     * 
     * @param point the Location of the mouse when pressed
     */
    public void onMousePress(Location point) {
        lastPoint = point;

        dragging = false;
        // test the selected student (which is on top) first.
        if (selectedHead.contains(point)) {
            dragging = true;
        } else {
            for (int imageNum = 0; imageNum<heads.length; imageNum++) {
                if (heads[imageNum].contains(point)) {
                    selectedHead = heads[imageNum];
                    dragging = true;
                    selectedHead.sendToFront();
                }
            }
        }

        // make the head being dragged bigger
        if (dragging) {
            selectedHead.setHeight(IMAGE_SIZE * DRAG_ZOOM);
            selectedHead.setWidth(IMAGE_SIZE * DRAG_ZOOM);
        }

    }

    /**
     * continue dragging if currently dragging
     * 
     * @param point the Location of the mouse when dragged
     */
    public void onMouseDrag(Location point) {
        if (dragging) {
            selectedHead.move(point.getX() - lastPoint.getX(),
                point.getY() - lastPoint.getY());
            lastPoint = point;
        }
    }

    /**
     * finish dragging operation
     * 
     * @param point the Location of the mouse release
     */
    public void onMouseRelease(Location point) {

        if (dragging) {
            selectedHead.setHeight(IMAGE_SIZE);
            selectedHead.setWidth(IMAGE_SIZE);
            dragging = false;
        }
    }
}