Question

I have created the following class implementing a ListSelectionListener interface. This class should “listen” to the selection events of a JList I have created. Everytime the use clicks on a row of this list, the selected_row value should be updated and the string “The format row selected is ….” should therefore change. However after clicking the rows more than once, the select_row value doesn’t change. Can anybody provide me a with an explanation for this and hopefully, a way to do what I want? Thanks in advance!!

import java.util.List;

import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;

import ee.dobax.portal.CommonPath;

public class FormatListSelectionListener implements ListSelectionListener{

public ContentGenerated content;
private CommonPathList path_list;
private ConfigRenderingDialog dialog;

public FormatListSelectionListener(ConfigRenderingDialog dialog){

    content = dialog.content;
    path_list = dialog.pathList;
}

public void valueChanged(ListSelectionEvent e) {
    int selected_row;

    if(e.getValueIsAdjusting() == false){
        selected_row = e.getLastIndex();


    System.out.println("The format row selected is "+selected_row);
        path_list.addFormatListRowSelected(selected_row);

        List<CommonPath> list_p = content.getPathList(selected_row);

        Object[] path_list_to_array = new Object[list_p.size()];

        path_list.getContents().removeAllElements();

        for(int x = 0; x < list_p.size(); x++){
            path_list_to_array[x] = list_p.get(x);
            path_list.getContents().addElement(path_list_to_array[x]);
            }

        }
  }


 }   

Answer 1

I read the docs as indicating that the ListSelectionEvent only tells you that the selection between firstIndex and lastIndex was changed, but not in which direction. Once you know that a change has occurred (that a ListSelectionEvent has been fired) you could just read the current selected value from the JList:

selected_row = ((JList) e.getSource()).getSelectedIndex();

You’ll want to check selected_row is non-negative, in case the user operation is simply unselecting the only selected option.