ballmover.java

书籍"Java_面向事件编程"的附带光盘代码

import objectdraw.*;

// Animator for a BallList
public class BallMover extends ActiveObject {
    
    private static final int PAUSETIME = 20;
    private static final double SPEED = 1;
    
    // the list of balls to animate
    private BallListInterface ballList;
    
    // distance that each ball should move
    private int distanceToMove;
    
    public BallMover(BallListInterface aList, int distance) {
        ballList = aList;
        distanceToMove = distance;
        
        start();
    }

    // move the specified ball
    private void moveOneBall(FilledOval ball) {
        double pixelsMoved = 0;
        while (pixelsMoved < distanceToMove) {
            ball.move(SPEED, 0);
            pause(PAUSETIME);
            pixelsMoved = pixelsMoved + SPEED;
        }
    }
    
    // traverse the list and move each ball once
    public void run() {
        while (!ballList.isEmpty()) {
            FilledOval ball = ballList.getFirst();
            moveOneBall(ball);
            ballList = ballList.getRest();
        }
    }
}