graphicsview.java

mvc模式的示例代码。输入球的半径

import java.util.Observer;
import java.util.Observable;
import java.awt.Graphics;
import java.awt.Canvas;
/**
 *
 * <p>Title: The View part of Application </p>
 * <p>Description: A class can implement the Observer interface when it wants to
 *  be informed of changes in observable objects. </p>
 * <p>Copyright: Copyright (c) 2005</p>
 * @author Smart Lee
 * @version 1.1
 */
public class GraphicsView extends Canvas implements Observer {
  // 定义鼠标坐标
  int x, y;
  // 定义球半径
  double radius;
  // 控制点坐标是否显示
  boolean bShowDim;
  //实现接口的方法
  public void update(Observable o, Object arg) {
    Sphere balloon = (Sphere) o;
    radius = balloon.getRadius();
  }
  // 绘球体
  public void paint(Graphics g) {

      int d = (int) radius * 2;
      int X = this.getWidth();
      int Y = this.getHeight(); // 注意不能在全局变量里设值！

      g.drawOval( (X - d) / 2, (Y - d) / 2, d, d);
      g.drawOval( (X - d) / 2, Y / 2 - d / 8, d, d / 4);
      g.drawOval(X / 2 - d / 8, (Y - d) / 2, d / 4, d);
      // 显示鼠标坐标
      if(bShowDim) {
        g.drawString("(" + x + ", " + y + ")", x, y);
      }
  }
}