chainreaction.java~

书籍"Java_面向事件编程"的附带光盘代码

import objectdraw.*;

// On a mouse press, the user can place balls on the canvas;
// On exiting the window, a simulation of a "chain reaction" begins:
// the most recently drawn ball hits into the second most recently drawn,
// which hits into the next ball, and so on.

public class ChainReaction extends WindowController {
    
    private RandomIntGenerator randomColor = new RandomIntGenerator(0, 255);
    
    // x and y coordinates of the first ball drawn
    private static final int BALL_X = 300;
    private static final int BALL_Y = 100;
    
    // ball diameter
    private static final int SIZE = 10;
    
    // distance between balls
    private static final int DISP = 2 * SIZE;
    
    // x coordinate of the next ball to be drawn
    private int ballX = BALL_X;
    
    // the list of all balls
    private BallListInterface ballList;
    
    public void begin() {
        // list of balls is empty at first
        ballList = new EmptyBallList();
    }
    
    // draws a ball
    public void onMousePress(Location point) {
        FilledOval ball = new FilledOval(ballX, BALL_Y, SIZE, SIZE, canvas);
        ballList = new NonEmptyBallList(ball, ballList);
        // update x coordinate for the next ball to be drawn
        ballX = ballX - DISP;
    }
    
    // cause the balls to begin hitting into each
    //  other in a "chain reaction"
    public void onMouseExit(Location point) {
        new BallMover(ballList, SIZE);
    }
}