radiobuttongroup.java

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     import java.awt.*;
     import java.util.*;

     // 维护一组按钮,这样在任意时刻只有一个被选中
     public class RadioButtonGroup extends Object
     {
          // 用来装单选按钮的动态可增长vector 
          protected Vector buttons;

          // 遍历上述Vector的枚举器
          protected Enumeration e;
          
          // 创建一个新的RadioButtonGroup对象
          public RadioButtonGroup()
          {
               buttons = new Vector();
          }

          // 将传入的单选按钮添加到vector中去
          public void add(RadioButton2D rb)
          {
               buttons.add(rb);
          }

          // 得到当前所选中的单选按钮
          //如果没有按钮被选中的话则返回null
          public RadioButton2D getSelection()
          {
               for(e = buttons.elements(); e.hasMoreElements(); )
               {
                    RadioButton2D rb = (RadioButton2D)e.nextElement();

                    if(rb.isSelected())
                    {
                         return rb;
                    }
               }

               return null;
          }

          // 整组按钮的可用/不可用状态
          public void setEnabled(boolean b)
          {
               for(e = buttons.elements(); e.hasMoreElements(); )
               {
                    ((RadioButton2D) e.nextElement()).setEnabled(b);
               }
          }

          // 设置整个按钮组的可见性 
          public void setVisible(boolean v)
          {
               for(e = buttons.elements(); e.hasMoreElements(); )
               {
                    ((RadioButton2D) e.nextElement()).setVisible(v);
               }
          }

          // 更新按钮组,让除了传入的按钮之外的按钮设置为未选中状态
          public void updateGroup(RadioButton2D rb)
          {
               for(e = buttons.elements(); e.hasMoreElements(); )
               {
                    Object o = e.nextElement();
                    if(rb != o)
                    {
                         ((RadioButton2D) o).setSelected(false);
                    }
               }
          }

          // 绘制组中的每一个按钮
          public void paint(Graphics2D g2d)
          {
               for(e = buttons.elements(); e.hasMoreElements(); )
               {
                    ((RadioButton2D)e.nextElement()).paint(g2d);
               }
          }

          // 在给定的位置绘制组中的每一个按钮
          public void paint(Graphics2D g2d, double dx, double dy)
          {
               for(e = buttons.elements(); e.hasMoreElements(); )
               {
                    ((RadioButton2D)e.nextElement()).paint(g2d, dx, dy);
               }
          }

     }    // RadioButtonGroup