Computer Science 252
Problem Solving with Java

Spring 2015, The College of Saint Rose

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DragStudentsS15 Demo

A working demo of DragStudentsS15 will appear below. Click inside the applet to interact with it.

DragStudentsS15 BlueJ Project

Click here to download a BlueJ project for DragStudentsS15.

DragStudentsS15 Source Code

The Java source code for DragStudentsS15 is below. Click on a file name to download it.

DragStudentsS15.java

import objectdraw.*;
import java.awt.*;
import java.util.Random;

/*
 * Example DragStudentsS15: drag around all of you!
 *
 * Jim Teresco, The College of Saint Rose, CSC 252, Spring 2015
 *
 * $Id: DragStudentsS15.java 2484 2014-11-17 04:10:26Z terescoj $
 */

public class DragStudentsS15 extends WindowController {

    // image sizes
    private static final int FULL_WIDTH = 125;
    private static final int FULL_HEIGHT = 141;
    private static final int SMALL_WIDTH = FULL_WIDTH/2;
    private static final int SMALL_HEIGHT = FULL_HEIGHT/2;

    // the array of image file names
    private String[] imageFiles = {
            "alec.jpg",
            "andrew.jpg",
            "catherine.jpg",
            "chris.jpg",
            "cody.jpg",
            "johnb.jpg",
            "johnr.jpg",
            "kat.jpg",
            "ken.jpg",
            "matt.jpg",
            "mattn.jpg",
            "michael.jpg",
            "michaelm.jpg",
            "mike.jpg",
            "ryan.jpg",
            "sm.jpg",
            "trevor.jpg"
        };

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

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

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

        // a larger canvas.
        setSize(600, 600);
        
        // we'll need to generate some random positions
        Random r = new Random();

        // construct the array of VisibleImage objects we'll need to remember - 
        // it will need to be the same length as the static array we
        // declared and constructed above
        heads = new VisibleImage[imageFiles.length];

        // place the images on the canvas randomly
        for (int imageNum = 0; imageNum < heads.length; imageNum++) {
            heads[imageNum] = new VisibleImage(getImage(imageFiles[imageNum]),
                r.nextDouble()*(canvas.getWidth() - SMALL_WIDTH),
                r.nextDouble()*(canvas.getHeight() - SMALL_HEIGHT),
                canvas);
            heads[imageNum].setWidth(SMALL_WIDTH);
            heads[imageNum].setHeight(SMALL_HEIGHT);

            // 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(r.nextDouble()*(canvas.getWidth() - SMALL_WIDTH),
                    r.nextDouble()*(canvas.getHeight() - SMALL_HEIGHT));
            }
        }

        // 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(FULL_HEIGHT);
            selectedHead.setWidth(FULL_WIDTH);
        }

    }

    /**
     * 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(SMALL_HEIGHT);
            selectedHead.setWidth(SMALL_WIDTH);
            dragging = false;
        }
    }
}