cloud.java~

书籍"Java_面向事件编程"的附带光盘代码

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

// Modified to produce some snow, sleet, and tomatoes
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 falling objects
    private RandomIntGenerator snowGen;  
    
    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;
        
        snowGen = new RandomIntGenerator( 0, screenWidth);
        
        start();
    }
    
    public void run() {
        int objCount = 0;
        
        // continue creating objects until the maximum amount
        // has been created
        while (objCount < MAX_OBJECTS ) {
            
            objCount++;
            
            // create snow, sleet or tomatoes, randomly
            switch (snowGen.nextValue() % 3) {
            case 0:
                new FallingSnow(canvas, snowPic, 
                                snowGen.nextValue(),   // x coordinate
                                snowGen.nextValue()*2/screenWidth+2, // y speed
                                screenHeight);
                break;
            case 1:
                new FallingSleet(canvas, snowGen.nextValue(),
                                 snowGen.nextValue()*4/screenWidth+2,
                                 screenHeight);
                break;
            case 2:
                new FallingTomato(canvas, snowGen.nextValue(),
                                  snowGen.nextValue()*4/screenWidth+2,
                                  screenHeight);
                break;
            }
            pause(PAUSETIME);
        }
    }
}