[2 days left] What’s wrong with your cloud strategy? Learn why multicloud solutions matter with Nimble Storage.Register Now

x
?
Solved

use action-listeners on userdefined objects in a canvas

Posted on 1998-08-18
7
Medium Priority
?
339 Views
Last Modified: 2008-03-03
I have a canvas containing objects ( which are ludo game
pieces here). For drawing these objects on the screen, they
contain x and y coordinates relative to the convas. What I need is actionListeners on every object, so that its not needed to verify the position of a mouse click, but directly  
jump to the actionPerformed method.

This easily done for buttons, menuItems and such but how do I make one for a component?
0
Comment
Question by:moonlight
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 4
  • 2
7 Comments
 
LVL 4

Expert Comment

by:evijay
ID: 1222040
are these objects extend from Component ?

If so, you can make these objects implement MouseListener and then in the mouseClicked method of it, fire a actionEvent.
You need to add the methods addActionListener and removeActionListener to these objects and maintain listeners in a vector. In the mouse click event, you need to invoke a fireActionEvent method (which you implement). In the fireActionEvent method, you create a ActionEvent, traverse thru the listener vector and invoke the actionPerformed method for each element in vector.

vijay

0
 
LVL 3

Accepted Solution

by:
mjenkins earned 400 total points
ID: 1222041
You need to derive your Object from Component, of course. Once that is done, make sure the objects implements

addActionListener()
removeActionListener()
protected void processEvent(AWTEvent e)
protected void processActionEvent(ActionEvent e)

0
 
LVL 3

Expert Comment

by:mjenkins
ID: 1222042
Here is a complete example just to make it easier to understand:

import java.awt.*;
import java.awt.event.*;
 
public class Act
        extends Canvas
{
    private ActionListener actionListener;
 
        public static void main( String args[] )
        {
                Frame f = new Frame( "Act" );
                f.setSize( 400,400 );
                Act a = new Act( );
                f.add( a );
                a.addActionListener( new ActionListener()
                        {
                                public void actionPerformed( ActionEvent e )
                                {
                                        System.out.println( "DONE" );
                                }
                        }
                );
                f.setVisible(true);
        }
 
        public Act()
        {
                setSize( 100,100 );
                enableEvents( AWTEvent.MOUSE_EVENT_MASK | AWTEvent.ACTION_EVENT_MASK );
        }
 
    public synchronized void addActionListener(ActionListener l)
        {
                actionListener = AWTEventMulticaster.add(actionListener, l);
    }
 
    public synchronized void removeActionListener(ActionListener l)
        {
                actionListener = AWTEventMulticaster.remove(actionListener, l);
    }
 
    protected void processEvent(AWTEvent e)
        {
        if (e instanceof MouseEvent)
                {
                        if( e.getID() == MouseEvent.MOUSE_RELEASED )
                processActionEvent( new ActionEvent(e.getSource(),ActionEvent.ACTION_PERFORMED, "ACTION!") );    
        }
                super.processEvent(e);
    }
 
    protected void processActionEvent(ActionEvent e)
        {
        if (actionListener != null)
                {
            actionListener.actionPerformed(e);
        }
    }
}

Notice that it is our responsibilty to convert the MouseEvent into an ActionEvent. I hope this puts the matter in perspective.
0
VIDEO: THE CONCERTO CLOUD FOR HEALTHCARE

Modern healthcare requires a modern cloud. View this brief video to understand how the Concerto Cloud for Healthcare can help your organization.

 
LVL 3

Author Comment

by:moonlight
ID: 1222043
Hi,
I've tested your sample code, but it doesnt respond the way I want it to. It doesnt matter where you click and I want it to. Isn't it what you should achieve with setSize(100,100) in Act () ?

How do I make an invisible area on the screen which will generate the object's actionPerformed() and send the object to it, when clicked on? as opposed to what I see now when it runs actionPerformed() on all clicks everywhere?
0
 
LVL 3

Expert Comment

by:mjenkins
ID: 1222044
The reason that it responds no matter where you click, is that the layout manager is resizing the component (even though I set it to 100,100). The default layout for Frame is BorderLayout. BorderLayout expands the "Center" component to the size of the container. If you insert:

f.setLayout( null );

right after

f.setSize(400,400);

You will see the behavior you are expecting. The app will print "DONE" only while clicking in the area bounded by 0,0,100,100.

You need to manage the size of your components in your actual application.
0
 
LVL 3

Expert Comment

by:mjenkins
ID: 1222045
Well, did it work? Are you satisfied with your answer?
0
 
LVL 3

Author Comment

by:moonlight
ID: 1222046
thank you for the help. sorry for dealy.
0

Featured Post

Concerto Cloud for Software Providers & ISVs

Can Concerto Cloud Services help you focus on evolving your application offerings, while delivering the best cloud experience to your customers? From DevOps to revenue models and customer support, the answer is yes!

Learn how Concerto can help you.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Java Flight Recorder and Java Mission Control together create a complete tool chain to continuously collect low level and detailed runtime information enabling after-the-fact incident analysis. Java Flight Recorder is a profiling and event collectio…
Go is an acronym of golang, is a programming language developed Google in 2007. Go is a new language that is mostly in the C family, with significant input from Pascal/Modula/Oberon family. Hence Go arisen as low-level language with fast compilation…
This theoretical tutorial explains exceptions, reasons for exceptions, different categories of exception and exception hierarchy.
How to fix incompatible JVM issue while installing Eclipse While installing Eclipse in windows, got one error like above and unable to proceed with the installation. This video describes how to successfully install Eclipse. How to solve incompa…
Suggested Courses

649 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question