actionlistenerinstaller.java

来自「这是java2核心技术第七版的源代码」· Java 代码 · 共 63 行

/**
   @version 1.00 2004-08-17
   @author Cay Horstmann
*/

import java.awt.event.*;
import java.lang.annotation.*;
import java.lang.reflect.*;

public class ActionListenerInstaller
{
   /**
      Processes all ActionListenerFor annotations in the given object.
      @param obj an object whose methods may have ActionListenerFor annotations
   */
   public static void processAnnotations(Object obj)
   {
      try
      {
         Class cl = obj.getClass();
         for (Method m : cl.getDeclaredMethods())
         {
            ActionListenerFor a = m.getAnnotation(ActionListenerFor.class);
            if (a != null) 
            {
               Field f = cl.getDeclaredField(a.source());
               f.setAccessible(true);
               addListener(f.get(obj), obj, m);
            }
         }
      }
      catch (Exception e)
      {
         e.printStackTrace();
      }
   }

   /**
      Adds an action listener that calls a given method.
      @param source the event source to which an action listener is added
      @param param the implicit parameter of the method that the listener calls
      @param m the method that the listener calls
   */
   public static void addListener(Object source, final Object param, final Method m)
      throws NoSuchMethodException, IllegalAccessException, InvocationTargetException
   {
      InvocationHandler handler = new
         InvocationHandler()
         {
            public Object invoke(Object proxy, Method mm, Object[] args) throws Throwable
            {
               return m.invoke(param);                    
            }
         };
   
      Object listener = Proxy.newProxyInstance(null,
         new Class[] { java.awt.event.ActionListener.class },
         handler);
      Method adder = source.getClass().getMethod("addActionListener", ActionListener.class);
      adder.invoke(source, listener);
   }
}