How To Have Code Run For A Real Time Update For Condition Met Without The Need Of An Event(Button Fo-CodePudding

I am trying to make a password checker, and I am trying to have an icon set as X until the user meets the condition of the password being at least 8 characters long. I am trying to set up a while loop for while the program is running, which will in turn run another while loop which will update the icon. I am doing this because a want it to always be checking to see if the condition is met and not need the user to click a button for example. I have placed the code inside the initComponents of the public form PasswordCheckerUI, but when I hit run on the program, it says running but my GUI doesn't pop up. How would I change the code to make this work(if needed) or where would I have to move it to? I have tried making a public static void with the code and calling it within the initCompnents, but it yielded the same results. Lastly, I tried to call the method within the main method, but the variables aren't static so that did not work either

public class PasswordCheckerUI extends javax.swing.JFrame {

    public PasswordCheckerUI() {
    initComponents();

    while (Thread.currentThread().isAlive()) {
        while (txtPassword.getText().length() < 8) {
            lblMinCharIcon.setIcon(X);

            if (txtPassword.getText().length() >= 8) {
                lblMinCharIcon.setIcon(Check);
            }
        }    

    }    
}

}

CodePudding user response：

Events in Swing don't just happen when the user clicks on a button - they happen all the time (when moving the mouse, when clicking, when editing text, when ...) and they are therefore the best way to solve your problem.

You can for example listen the document change events on the txtPassword and change the icon depending on the new length of the password:

public class PasswordCheckerUI {
    private JTextField txtPassword;
    private JLabel lblMinCharIcon;

    public PasswordCheckerUI() {
        txtPassword = new JTextField(40);
        txtPassword.getDocument().addDocumentListener(
            new DocumentListener() {
                @Override
                public void insertUpdate(DocumentEvent e) {
                    checkPasswordLen(txtPassword);
                }

                @Override
                public void removeUpdate(DocumentEvent e) {
                    checkPasswordLen(txtPassword);
                }

                @Override
                public void changedUpdate(DocumentEvent e) {
                    checkPasswordLen(txtPassword);
                }
            }
        );
    }

    private void checkPasswordLen(JTextField tf) {
        if (tf.getText().length() < 8) {
            lblMinCharIcon.setIcon(x);
        } else {
            lblMinCharIcon.setIcon(check);
        }
    }
}