JPanel Action Listener

Question

I have a JPanel with a bunch of different check boxes and text fields, I have a button that\'s disabled, and needs to be enabled when specific configurations are setup. What

Answer 1

A suggestion could be to derive a class from each of the components you're using and add an ActionListener that bubbles up the Container tree and looks for the first Container that implements a custom interface like this:

public interface MyCommandProcessor {
  void execute(String actionCommand);
}

public class MyButton extends JButton {
  public MyButton(string actionCommand) {
    setActionCommand(actionCommand);
    addActionListener(new ActionListener() {
      @Override
      public void actionPerformed(ActionEvent ae) {
        Container traverser = MyButton.this;
        while (traverser != null && !(traverser instanceof MyCommandProcessor))
          traverser = traverser.getParent();
        if (traverser != null)
          ((CommandListener)traverser).execute(ae.getActionCommand());
      }
    });
  }
}

public class MyApp extends JFrame implements MyCommandListener {
  public MyApp() {
    JPanel panel = new Panel();
    panel.add(new MyButton("MyButton got pressed"));
  }

  public void execute(String actionCommand) {
    System.out.println(actionCommand);
  }
}

Answer 2

You need to create custom component listener. Look here:

Create a custom event in Java

Creating Custom Listeners In Java

http://www.javaworld.com/article/2077333/core-java/mr-happy-object-teaches-custom-events.html

I do it throw the standard ActionListener Example

public class MyPanel extends JPanel {
  private final  JComboBox<String> combo1;
  private final JButton btn2;

  .......
   //catch the actions of inside components
   btn2.addActionListener(new MyPanelComponentsActionListener());
  ........

   //assign actionlistener to panel class
    public void addActionListener(ActionListener l) {
        listenerList.add(ActionListener.class, l);
    }
    public void removeActionListener(ActionListener l) {
        listenerList.remove(ActionListener.class, l);
    }

    //handle registered listeners from components used MyPanel class
   protected void fireActionPerformed(ActionEvent event) {
    // Guaranteed to return a non-null array
    Object[] listeners = listenerList.getListenerList();
    ActionEvent e = null;
    // Process the listeners last to first, notifying
    // those that are interested in this event
    for (int i = listeners.length-2; i>=0; i-=2) {
        if (listeners[i]==ActionListener.class) {
            // Lazily create the event:
            if (e == null) {
                  String actionCommand = event.getActionCommand();
                  if(actionCommand == null) {
                     actionCommand = "FontChanged";
                  }
                  e = new ActionEvent(FontChooserPanel.this,
                                      ActionEvent.ACTION_PERFORMED,
                                      actionCommand,
                                      event.getWhen(),
                                      event.getModifiers());
             }
                 // here registered listener executing
                ((ActionListener)listeners[i+1]).actionPerformed(e); 
            }
        }
    }

//!!! here your event generator
    class MyPanelComponentsActionListener implements ActionListener  {
     public void actionPerformed(ActionEvent e) {
        //do something usefull
        //.....
        fireActionPerformed(e); 
      }
     }
....
}

Answer 3

First off as @Sage mention in his comment a JPanel is rather a container than a component which do action. So you can't attach an ActionListener to a JPanel.

I figure I can copy and paste my code a bunch of times into every listener in the panel, but that seems like bad coding practice to me.

You're totally right about that, it's not a good practice at all (see DRY principle). Instead of that you can define just a single ActionListener and attach it to your JCheckBoxes like this:

final JCheckBox check1 = new JCheckBox("Check1");
final JCheckBox check2 = new JCheckBox("Check2");
final JCheckBox check3 = new JCheckBox("Check3");

final JButton buttonToBeEnabled = new JButton("Submit");
buttonToBeEnabled.setEnabled(false);

ActionListener actionListener = new ActionListener() {
    @Override
    public void actionPerformed(ActionEvent e) {
        boolean enable = check1.isSelected() && check3.isSelected();
        buttonToBeEnabled.setEnabled(enable);
    }
};

check1.addActionListener(actionListener);
check2.addActionListener(actionListener);
check3.addActionListener(actionListener);

This means: if check1 and check3 are both selected, then the button must be enabled, otherwise must be disabled. Of course only you know what combination of check boxes should be selected in order to set the button enabled.

Take a look to How to Use Buttons, Check Boxes, and Radio Buttons tutorial.