cloud.java

书籍"Java_面向事件编程"的附带光盘代码

import java.awt.Image;

import objectdraw.ActiveObject;
import objectdraw.DrawingCanvas;
import objectdraw.RandomIntGenerator;

// Modified to produce some snow and some sleet
public class Cloud extends ActiveObject {
    
    // total number of falling objects
    private static final int MAX_OBJECTS = 150;
    
    // how long to pause between creating objects
    private static final int PAUSETIME = 900;
    
    // the canvas
    private DrawingCanvas canvas;
    
    // picture of a snowflake
    private Image snowPic;
    
    // size of the screen
    private int screenWidth, screenHeight;
    
    // used to generate random speeds and positions for snowflakes
    private RandomIntGenerator objGen;
    
    public Cloud(
                 Image aSnowPic,
                 int aScreenWidth,
                 int aScreenHeight,
                 DrawingCanvas aCanvas) {
        
        // save the parameters for the "run" method
        canvas = aCanvas;
        snowPic = aSnowPic;
        screenWidth = aScreenWidth;
        screenHeight = aScreenHeight;
        
        objGen = new RandomIntGenerator(0, screenWidth);
        
        start();
    }
    
    public void run() {
        int objCount = 0;
        
        // continue creating snow and sleet until the maximum amount
        // has been created
        while (objCount < MAX_OBJECTS) {
            
            objCount++;
            
            // create snow or sleet, randomly
            if (objGen.nextValue() % 2 == 0) {
                new FallingSnow(
                                canvas,
                                snowPic,
                                objGen.nextValue(),  // x coordinate
                                objGen.nextValue() * 2 / screenWidth + 2, // y speed
                                screenHeight);
            } else {
                new FallingSleet(
                                 canvas,
                                 objGen.nextValue(),
                                 objGen.nextValue() * 4 / screenWidth + 2,
                                 screenHeight);
            }
            pause(PAUSETIME);
        }
    }
}