Question

I’m trying to make a Swing Timer that is executes when I press a button but never starts.
My code is:

public class prueba extends JFrame {
    java.util.Date date= new java.util.Date();
    private JPanel contentPane;
    Timer timero;
        ........

public prueba() {
         ..........
        timero  = new Timer(1000, new ActionListener() {
            public void actionPerformed(ActionEvent e) {
              System.out.println("otra vez....uauuauauaua");
            }
          });
        btnIniciar.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                  timero.start();
                                  ...............

Could you help me please?
Thanks and sorry for my english!

When I do these I have an error:

public class prueba extends JFrame {
    java.util.Date date= new java.util.Date();
    private JPanel contentPane;
    Timer timero;

public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {
        public void run() {
            try {
                prueba frame = new prueba();
                frame.setVisible(true);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    });
}

public prueba() {




    final WebManager web = new WebManager("user","pass","http://www.spanishtracker.com/login.php");
    //web.EnableDebug();
    web.doLogin();
    web.getCookies;
        .....
    contentPane.add(txtSalida, gbc_txtSalida);

    timero.start();

it gives me an error:

java.lang.NullPointerException
    at prueba.<init>(prueba.java:216)
    at prueba$1.run(prueba.java:56)
    at java.awt.event.InvocationEvent.dispatch(Unknown Source)
    at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
    at java.awt.EventQueue.access$400(Unknown Source)
    at java.awt.EventQueue$2.run(Unknown Source)

These lines are:
216         timero.start();
56      prueba frame = new prueba();

Answer 1

You may have another Timer named timero that shadows the one on which you call .start(). For reference, this example shows how to start and stop a timer, and this example shows how to expose a start() method that forwards to an enclosed timer. The latter is useful to avoid starting the timer prematurely, before the constructor concludes.