credit.java~

书籍"Java_面向事件编程"的附带光盘代码

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

public class Credit extends ActiveObject {

    private static final double SPEED_PER_MILLI = 0.04;
    private static final int DELAY_TIME = 100;
    
    private Text roleAndName; // information to be displayed
    
    private double distance;     // how far the text has moved

    public Credit(String scrollingLine, DrawingCanvas canvas) {
        distance = 0;
        // create the line to be displayed
        roleAndName = new Text(scrollingLine, 0, canvas.getHeight(), canvas);
        // center it on the canvas
        roleAndName.move((canvas.getWidth() - roleAndName.getWidth())/2, 0);
        // start the movement
        start();
    }
    
    public void run() {
        double lastTime, currentTime, elapsedTime;
        // remember the time;
        lastTime = System.currentTimeMillis();
        while (roleAndName.getY() > -roleAndName.getHeight()) {
            // determine how much time has passed
            currentTime = System.currentTimeMillis();
            elapsedTime = currentTime - lastTime;
            // restart timing
            lastTime = currentTime;
            roleAndName.move(0, -SPEED_PER_MILLI * elapsedTime);
            distance = distance + -SPEED_PER_MILLI * elapsedTime;
            pause(DELAY_TIME);
        }
        roleAndName.removeFromCanvas();
    }

    public double getHeight( ) {
        return roleAndName.getHeight();
    }

    public double distanceTraveled( ) {
        System.out.println(distance);
        return distance;
    }
}