Controlling a label's text with Threads

Question

Hello,
I couldn't find a specific topic about Java Threads and that's why i am writing here.
I am developing a kind of strategy game and in one module i need to show the total amount of money the user has.
- at first, when the game starts, the player chooses an amount.
- the game starts and the player buys something
- the amount should be updated, for a logical and routine transaction.
But since the frame which is responsible from such transactions differ from the main frame, i could not do the update operations.
e.g.
public class GameMain extends JFrame{
//The label is here
}//end of gamemain
class TransactionFrame extends JInternalFrame{
//The internal frame has some buttons and radio buttons to allow the user to make transactions, purchasing of certain tools
}//end of transactionframeThe best way that came into my mind was to update the label in my GameMain class whenever the player selects , say "Add" button in TransactionFrame.
I had many tests before to do it with a certain paint method to handle those issues, but i couldn't find a solution.
On the other hand, the TransactionFrame class' instances are created in some other class which I think wouldn't be relevant to say here, because it does nothing to do here.
What i want to do is, as defined above,
- i want to update the label in GameMain and
- it should be updated whenever "Add" button is clicked in the TransactionFrame, which is a JInternalFrame.
Here is what i have tried:
1. i added a flag value in the TransactionFrame's "Add" button, and whenever it becomes "true", the Thread controlling the Label's text of GameMain, is triggered
and the new amount will be presented to the user.
-->But, although the player doesn't click anything on the internal frame, the thread in the main frame consideres it as clicked and tries to run something else.
2. the other thing is, I put the amount at the internal frame as a string (drawn in paint method of this frame),
--> This time, I updated the amount here but whenever I close the frame and create the frame by clicking on some button, the amount remains as chosen in the starting phase.
(e.g. user selected 5000$, then bought something, the new amount: 4000$, ok, i close the frame and reopen it, the amount is: 5000$ !).
I hope that I described the problem clearly here,
What i expect is given above, if you'd like to advice me to try other things, please do not hesitate.
Thank you,
led1433

Answer 1

You're probably long gone, so I'm not sure you'll see this, but my opinion is that your next step is to try to decrease the cohesion (I think that's what it's called) of your code so that the code that represents your main GUI has little knowledge of the code that represents the JInternalFrame and visa versa. I'm no pro at this, but one way to possibly do this is to give both public methods that get and set the amount and then let a Controller class call these methods. For instance:
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
public class Test3B {
  private static void createAndShowUI() {
    final Main3B main = new Main3B();
    main.getComponent().setPreferredSize(new Dimension(500, 400));
    final Internal3B internalGui = new Internal3B();
    internalGui.addSetAmountBtnListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        String amtString = internalGui.getAmountFieldText().trim();
        try {
          int amount = Integer.parseInt(amtString);
          main.setAmount(amount);
        } catch (NumberFormatException nfe) {
          JOptionPane.showMessageDialog(main.getComponent(), "Enter integers only",
              "Error", JOptionPane.ERROR_MESSAGE);
    JInternalFrame internalFrame = new JInternalFrame();
    internalFrame.getContentPane().add(internalGui.getMainPanel());
    internalFrame.setBounds(10, 10, 400, 300);
    internalFrame.setClosable(true);
    main.addInternalFrame(internalFrame);
    JFrame frame = new JFrame("Test3B");
    frame.getContentPane().add(main.getComponent());
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.pack();
    frame.setLocationRelativeTo(null);
    frame.setVisible(true);
  public static void main(String[] args) {
    java.awt.EventQueue.invokeLater(new Runnable() {
      public void run() {
        createAndShowUI();
class Main3B {
  private static final String AMOUNT_LABEL = "Amount is: ";
  private int amount = 0;
  private JPanel mainPanel = new JPanel();
  private JLabel amountLabel = new JLabel(AMOUNT_LABEL + amount, SwingConstants.LEFT);
  private JDesktopPane desktop = new JDesktopPane();
  public Main3B() {
    desktop.setBorder(BorderFactory.createLineBorder(Color.blue));
    mainPanel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
    mainPanel.setLayout(new BorderLayout());
    mainPanel.add(amountLabel, BorderLayout.NORTH);
    mainPanel.add(desktop, BorderLayout.CENTER);
  public void addInternalFrame(JInternalFrame internalFrame) {
    desktop.add(internalFrame);
    internalFrame.setVisible(true);
  public void setAmount(int amount) {
    this.amount = amount;
    amountLabel.setText(AMOUNT_LABEL + amount);
  public int getAmount() {
    return amount;
  public JComponent getComponent() {
    return mainPanel;
class Internal3B {
  private JPanel mainPanel = new JPanel();
  private JTextField amountField = new JTextField(10);
  private JButton setAmountBtn = new JButton("Set Amount");
  public Internal3B() {
    mainPanel.add(new JLabel("Enter New Amount:"));
    mainPanel.add(Box.createHorizontalStrut(5));
    mainPanel.add(amountField);
    mainPanel.add(Box.createHorizontalStrut(15));
    mainPanel.add(setAmountBtn);
  public JPanel getMainPanel() {
    return mainPanel;
  public String getAmountFieldText() {
    return amountField.getText();
  public void addSetAmountBtnListener(ActionListener al) {
    setAmountBtn.addActionListener(al);
}