MouseListener inside loop isnt using updated variable values

Question

I want to first apologize for my poor English. I made some JPanels which I'm putting inside one JPanel and this last JPanel I'm putting it in one JScrollPane, each Jpanel has some JLabels that have text inside them. I've done that and everything is working until now, then I added a mouseListener to System.out.print the text inside the JLabels. The texts are different, but on the console I'm getting the same text, here's my code:

/*
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 */
package testa;

import java.awt.Color;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.GridLayout; 
import java.io.IOException;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import java.awt.event.*;

public class Test extends JFrame{ //see https://www.javatpoint.com/java-naming-conventions

    private JLabel[] titles;
    private JLabel[] descriptions;
    private JPanel [] panels;
    private JScrollPane jScrollPane1;
    private JPanel bigPanel;
    private final static int NUM_OF_RESULTS =10;
String identifier ;
String title;
String authors;
String resume;
String references;
    public Test() throws IOException {
        
        setLocationRelativeTo(null);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setSize(1000,500);            
        //jScrollPane1.setSize(1000, 500);    and layouts. see following comments

        bigPanel = new JPanel();
        bigPanel.setBounds(30, 90, 950, 400);
        //set layout to
        GridLayout layout = new GridLayout(NUM_OF_RESULTS, 0);
        bigPanel.setLayout(layout);
        jScrollPane1 = new JScrollPane(bigPanel);
        jScrollPane1.setBounds(30, 90, 950, 400);
        getContentPane().add(jScrollPane1);

        requetezQuery();
        //pack(); //see https://stackoverflow.com/questions/22982295/what-does-pack-do
        setVisible(true); //set visible typically comes last
    }
    public void requetezQuery() {
            
int actual=0;


     

        
        
        titles = new JLabel[NUM_OF_RESULTS];
        descriptions = new JLabel[NUM_OF_RESULTS];
        panels = new JPanel[NUM_OF_RESULTS];

        for(int i = 0; i<NUM_OF_RESULTS; i++){
                       
                         title = "Title "+i;
                      resume = "Description "+i ;

            titles[i]= new JLabel();
            descriptions[i]= new JLabel();
            panels[i]= new JPanel();
            panels[i].setPreferredSize(new Dimension(250, 50));
            panels[i].setLayout(new FlowLayout()); //FlowLayout is default for JPanel
            titles[i].setText(title);
            
            descriptions[i].setText(resume.substring(0, Math.min(resume.length(), 100))+"...");
            titles[i].setForeground(Color.blue);
            descriptions[i].setForeground(Color.black);
            titles[i].addMouseListener(new MouseAdapter() { 
          public void mouseClicked(MouseEvent me) { 
            System.out.println(title);
          } 
        });
            panels[i].add(titles[i]);
            panels[i].add(descriptions[i]);
            bigPanel.add(panels[i],i, 0);
             
        }
        
    }
    

    public static void main(String args[]) throws IOException{
        new Test();
    }
}

score 2 · Accepted Answer · answered May 19 '18 at 13:24

I believe your reference to title refers to the last created title at runtime. What you can do to fix this is instead of printing the title, print the labels text. Try putting this inside of your mouseClicked method.

JLabel obj = (JLabel) me.getSource();
System.out.println(obj.getText());

score 0 · Answer 2 · answered May 19 '18 at 14:56

Your mouse click event reference variable from outer class:

    addMouseListener(new MouseAdapter() { 
      public void mouseClicked(MouseEvent me) { 
        System.out.println(title); // This `title` is a reference of Test.title variable
      } 
    });

So all of your MouseAdapter references the same title (whose value is replaced by each loop) -> System.out.println all prints the same last title.

MouseListener inside loop isnt using updated variable values

2 Answers2