Java Help - Communicating from event handler to container

Author

Communicating from event handler to container

eastside

2007-02-25, 10:08 pm

I have a class, let's call it AC, which extends JPanel. Each instance of AC
also contains a JTextField. The actionlistener for the text field is also in
the class definition of AC. If a certain condition is detected by the
actionlistener, the object needs to tell the parent object that contains AC
to inform all other instances of AC that they need to be updated. How is
this communication back to the parent object usually accomplished in Java?
Thanks!

Michael Dunn

2007-02-26, 4:16 am

On Feb 26, 1:32 pm, "eastside" <easts...@spamarrest.com> wrote:
> I have a class, let's call it AC, which extends JPanel. Each instance of AC
> also contains a JTextField. The actionlistener for the text field is also in
> the class definition of AC. If a certain condition is detected by the
> actionlistener, the object needs to tell the parent object that contains AC
> to inform all other instances of AC that they need to be updated. How is
> this communication back to the parent object usually accomplished in Java?
> Thanks!

maybe(??) this might do what you want

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
class Testing
{
public void buildGUI()
{
JPanel p = new JPanel(new GridLayout(5,1));
for(int x = 0; x < 5; x++) p.add(new AC());
JFrame f = new JFrame();
f.getContentPane().add(p);
f.pack();
f.setLocationRelativeTo(null);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setVisible(true);
}
public static void main(String[] args)
{
SwingUtilities.invokeLater(new Runnable(){
public void run(){
new Testing().buildGUI();
}
});
}
}
class AC extends JPanel
{
static java.util.List acPanels = new java.util.ArrayList();
JTextField tf = new JTextField(5);
public AC()
{
acPanels.add(this);
add(tf);
tf.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent ae){
for(int x = 0, y = acPanels.size(); x < y; x++)
{
AC acPanel = (AC)acPanels.get(x);
acPanel.tf.setText(acPanel.tf.getText()+x);
}
}
});
}
}

eastside

2007-02-26, 10:12 pm

"Michael Dunn" <m_odunn@yahoo.com> wrote in message
news:1172464061.584984.63560@j27g2000cwj.googlegroups.com...
> On Feb 26, 1:32 pm, "eastside" <easts...@spamarrest.com> wrote:
>
>
> maybe(??) this might do what you want
>
> import javax.swing.*;
> import java.awt.*;
> import java.awt.event.*;
> class Testing
> {
> public void buildGUI()
> {
> JPanel p = new JPanel(new GridLayout(5,1));
> for(int x = 0; x < 5; x++) p.add(new AC());
> JFrame f = new JFrame();
> f.getContentPane().add(p);
> f.pack();
> f.setLocationRelativeTo(null);
> f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
> f.setVisible(true);
> }
> public static void main(String[] args)
> {
> SwingUtilities.invokeLater(new Runnable(){
> public void run(){
> new Testing().buildGUI();
> }
> });
> }
> }
> class AC extends JPanel
> {
> static java.util.List acPanels = new java.util.ArrayList();
> JTextField tf = new JTextField(5);
> public AC()
> {
> acPanels.add(this);
> add(tf);
> tf.addActionListener(new ActionListener(){
> public void actionPerformed(ActionEvent ae){
> for(int x = 0, y = acPanels.size(); x < y; x++)
> {
> AC acPanel = (AC)acPanels.get(x);
> acPanel.tf.setText(acPanel.tf.getText()+x);
> }
> }
> });
> }
> }

First of all, thanks for going to all that effort to provide a solution!

However, there is a real need for the object to communicate back to the
parent object. My thought was something like this:

class Testing {
MainObj parentObj; // ref to parent object

public void buildGUI() {
JPanel p = new JPanel(new GridLayout(5,1));
for(int x = 0; x < 5; x++) p.add(new AC());
JFrame f = new JFrame();
f.getContentPane().add(p);
f.pack();
f.setLocationRelativeTo(null);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable(){
public void run(){
new Testing().buildGUI();
}
}
);
}
}

class AC extends JPanel {
static java.util.List acPanels = new java.util.ArrayList();

public AC(MainObj MO) { // constructor requires parent object reference

parentObj = MO; // save reference
acPanels.add(this);
add(tf);
tf.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent ae){
....do some stuff
parentObj.callBack(...) // call the parent object to notify that update
must occur
}
});
}
}

My thought there already must be a mechanism in place to do this.

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