component2d.java

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     import java.awt.*;
     import java.awt.geom.*;

     // 创建可视化组件的基类 
     public abstract class Component2D extends Object 
     {
          // 容纳组件外观的ImageGroup 
          protected ImageGroup group;

          // 组件的大小
          protected int frameWidth;
          protected int frameHeight;

          // 组件的位置和边界,以及缓存的变换
          protected Vector2D pos;
          protected Rectangle2D bounds;
          protected AffineTransform xform;

          // 组件是否可视是否可用的标记
          protected boolean enabled;
          protected boolean visible;

          // 跟踪组件的内部状态
          protected int state;

          // 用默认的属性创建一个新的Component2D对象
          protected Component2D()
          {
               pos = new Vector2D.Double();
               xform = new AffineTransform();

               setEnabled(true);
               setVisible(true);

               bounds = new Rectangle2D.Double();
               frameWidth  = 0;
               frameHeight = 0;

               state = 0;
          }

          // 使用传入的Graphics2D容器绘制组件
          public abstract void paint(Graphics2D g2d);

          // 在给定的偏移位置绘制组件 
          public abstract void paint(Graphics2D g2d, double dx, double dy);

          // 更新组件内部的变换
          public void update()
          {
               xform.setToTranslation(pos.getX(), pos.getY()); 
          }

          // 更新组件的边界矩形
          public void updateBounds()
          {
               if(frameWidth <= 0 && group != null)
               {
                    frameWidth = group.getFrameWidth();
               }
               if(frameHeight <= 0 && group != null)
               {
                    frameHeight = group.getFrameHeight();
               }

               bounds.setRect(pos.getX(), pos.getY(), frameWidth, frameHeight);
          }

          // 返回一个描述组件的String
          public String toString()
          {
               // 输出类名合当前位置
               return getClass().getName() + ": " + pos.toString();
          }

          // 主要属性的访问方法

          public void setEnabled(boolean e)
          {
               enabled = e;
          }

          public final boolean isEnabled()
          {
               return enabled;
          }

          public final void setVisible(boolean v)
          {
               visible = v;
          }

          public final boolean isVisible()
          {
               return visible;
          }

          public final void setX(double px)
          {
               pos.setX(px);
          }

          public final void setY(double py)
          {
               pos.setY(py);
          }

          public final double getX()
          {
               return pos.getX();
          }

          public final double getY()
          {
               return pos.getY();
          }

          public final void setPos(int x, int y)
          {
               pos.setX(x);
               pos.setY(y);
          }

          public final void setPos(double x, double y)
          {
               pos.setX(x);
               pos.setY(y);
          }
 
          public final void setPos(Vector2D v)
          {
               pos.setX(v.getX());
               pos.setY(v.getY());
          }

          public final Vector2D getPos()
          {
               return pos;
          }

          public Rectangle2D getBounds()
          {
               return bounds;
          }

     }    // Component2D