Trying to display a variable created in one jpanel and display it in another jpanel

Question

I'm a student programming a frogger game, when the frog collides with an object or reaches the end zone either the score is incremented or lives decremented and the frog returned to the start position. this section works and the decrement and increment work when outputting them to the console, I try to pass the variable to the other jpanel and display it there but it doesnt update and display the variable in the textField.

Game Panel

    public GamePanel() {
    super();
    setFocusable(true);
    addKeyListener(new KeyList());
    System.out.println("GAME PANE FOCUS:" + this.isFocusOwner());

    scores.setVisible(true);
    lives = p.STARTLIVES;
    scores.setCurrentLives(lives);
    txtTest.setText("Hello");
    txtTest.setVisible(true);
    add(scores,new AbsoluteConstraints(0,550,50,800));
    Boolean displayable = scores.isDisplayable();
    System.out.println("Displayable" + displayable);

    scores.setEnabled(false);
    scores.revalidate();
    scores.repaint();
    scores.setVisible(true);

    System.out.println("Displayable" + displayable);



   car1.start();
   car2.start();
   car3.start();
   car4.start();
   Log1.start();
   Log2.start();
   Log3.start();
   Log4.start();
   Log5.start();
   Log6.start();
   Log7.start();
   Log8.start();



    //check for collisions
}

final public void winZone(Rectangle object){

    if(myFrog.frogArea().intersects(object)){
        currentScore = currentScore + 100;
        System.out.println("current Score " + currentScore);
        p.setScore(currentScore);
        scores.myScore().setText("hello");

        myFrog.lostLife();
    }

scores panel

public class jplScores extends JPanel {
 Properties p = new Properties();
 int currentLives;
 int i;

/** Creates new form jplScores */
public jplScores() {
    initComponents();




}
public void setCurrentLives(int Lives){
 currentLives = Lives;
}
public String getCurrentLives(){
    String L = Integer.toString(currentLives);
    return L;
}


public JTextField myScore(){
    return txtScore;
}

Currently it will display the jpanel from the frame that they are both in but i have tried to make it so its a panel within a panel but i cant get the panel to display from within the game panel.

Any help would be great thanks

    public FroggerGame() {

    initComponents();
    setFocusable(true);
    //repaint();
   // p.setHeight(550);
   // p.setWidth(800);
   // p.setLives(3);
   // p.setScore(0);
    PANELHEIGHT = p.getHeight();
    PANELWIDTH = p.getWidth();
    welcomePanel();

    /*
    Toolkit tool = Toolkit.getDefaultToolkit();
    imgBackground = tool.getImage(imageBackground);
    background = new ImageIcon(imgBackground);
    //setDefaultCloseOperation(EXIT_ON_CLOSE);
    */

    jps.myScore().addPropertyChangeListener(new java.beans.PropertyChangeListener() {
        public void propertyChange(java.beans.PropertyChangeEvent evt) {
           // txtScorePropertyChange(evt);

    jps.myScore().setText(Integer.toString(gp.currentScore()));
    System.out.println(Integer.toString(gp.currentScore()));

    jps.getScore(gp.currentScore());
    System.out.println(" main score " + gp.currentScore());
        }
    });


}

....

private void btnEnterActionPerformed(ActionEvent evt) {

    welcomePanel.setVisible(false);
    getContentPane().setLayout(new AbsoluteLayout());
    getContentPane().add(gp,new AbsoluteConstraints(0,0,800,550));
    getContentPane().add(jps,new AbsoluteConstraints(0,550,800,100));

    //gp.setSize(800, 550);
   // gp.setBounds(0, 0, 800, 550);
    gp.setVisible(true);
    gp.requestFocusInWindow();

    jps.setVisible(true);

gp is the game panel and jps is the score panel.

Answer 1

This really has little to do with "panels" or Swing GUI coding and all to do with the basic OOPS issue of passing information from one class to another. One way to solve this is to give your Scores panel a public method, say

public void changeScore(int value) {
   // in here add the new value to the currently 
   // displayed value and display the new value.
}

Then the main class, the one with a Scores panel reference, you can call this method, passing in 1 if score is to increase or -1 if it is to decrease.

I think of this as the "push" solution, where one class pushes information into the other class. Another way to solve this is via listeners where the Scores class listens to critical properties of the other class and then changes its own score when an appropriate event occurs, and this often involves using PropertyChangeListeners or other more Swing-specific listener classes. This is sometimes a nicer solution, but I consider it a slightly more advanced concept.