Event Tracer
/*
This program is a part of the companion code for Core Java 8th ed.
(http://horstmann.com/corejava)
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.Container;
import java.awt.EventQueue;
import java.beans.BeanInfo;
import java.beans.EventSetDescriptor;
import java.beans.IntrospectionException;
import java.beans.Introspector;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JSlider;
/**
* @version 1.13 2007-06-12
* @author Cay Horstmann
*/
public class EventTracerTest
{
public static void main(String[] args)
{
EventQueue.invokeLater(new Runnable()
{
public void run()
{
JFrame frame = new EventTracerFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
});
}
}
class EventTracerFrame extends JFrame
{
public EventTracerFrame()
{
setTitle("EventTracerTest");
setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);
// add a slider and a button
add(new JSlider(), BorderLayout.NORTH);
add(new JButton("Test"), BorderLayout.SOUTH);
// trap all events of components inside the frame
EventTracer tracer = new EventTracer();
tracer.add(this);
}
public static final int DEFAULT_WIDTH = 400;
public static final int DEFAULT_HEIGHT = 400;
}
/*
This program is a part of the companion code for Core Java 8th ed.
(http://horstmann.com/corejava)
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/**
* @version 1.31 2004-05-10
* @author Cay Horstmann
*/
class EventTracer
{
public EventTracer()
{
// the handler for all event proxies
handler = new InvocationHandler()
{
public Object invoke(Object proxy, Method method, Object[] args)
{
System.out.println(method + ":" + args[0]);
return null;
}
};
}
/**
* Adds event tracers for all events to which this component and its children can listen
* @param c a component
*/
public void add(Component c)
{
try
{
// get all events to which this component can listen
BeanInfo info = Introspector.getBeanInfo(c.getClass());
EventSetDescriptor[] eventSets = info.getEventSetDescriptors();
for (EventSetDescriptor eventSet : eventSets)
addListener(c, eventSet);
}
catch (IntrospectionException e)
{
}
// ok not to add listeners if exception is thrown
if (c instanceof Container)
{
// get all children and call add recursively
for (Component comp : ((Container) c).getComponents())
add(comp);
}
}
/**
* Add a listener to the given event set
* @param c a component
* @param eventSet a descriptor of a listener interface
*/
public void addListener(Component c, EventSetDescriptor eventSet)
{
// make proxy object for this listener type and route all calls to the handler
Object proxy = Proxy.newProxyInstance(null, new Class[] { eventSet.getListenerType() },
handler);
// add the proxy as a listener to the component
Method addListenerMethod = eventSet.getAddListenerMethod();
try
{
addListenerMethod.invoke(c, proxy);
}
catch (InvocationTargetException e)
{
}
catch (IllegalAccessException e)
{
}
// ok not to add listener if exception is thrown
}
private InvocationHandler handler;
}
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