grass.java~

书籍"Java_面向事件编程"的附带光盘代码

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

// Class that allows a user to draw a grassy scene
public class Grass extends WindowController {
    
    // level of the horizon
    private static final int GROUND_LINE = 270;
    
    // position and radius of the sun
    private static final int SUN_INSET = 50,      
                             SUN_SIZE = 75;

    // level and spacing of the blades of grass
    private static final int GRASS_TOP = 255,
                             GRASS_SPACING = 2;

    double bladePosition; // x coordinate of next blade of grass
    
    public void begin() {
        // draw solid ground and sun
        new FilledRect(0, GROUND_LINE, canvas.getWidth(),
                       canvas.getHeight()-GROUND_LINE, canvas );
        new FilledOval(SUN_INSET, SUN_INSET, SUN_SIZE, SUN_SIZE,
                       canvas);
        bladePosition = 0;
    }

    public void onMouseClick(Location point) {
        // grow a blade of grass with each mouse click
        if (bladePosition < canvas.getWidth()){
            new Line(bladePosition, GRASS_TOP, bladePosition, GROUND_LINE, 
                     canvas);
            bladePosition = bladePosition + GRASS_SPACING;
        }
    }
}