从一个类到另一个使用JTextField

Question

I am trying to use a JTextField from my class A in a class B. I have done some research but I cannot seem to find the answer.

Here is how my class A looks like:

public A extends JFrame implements ActionListener {
  public A(){
    chrono = new JTextField("" + sec); // déclarer final car une classe interne va acceder à ce composant 
    chrono.setHorizontalAlignment(SwingConstants.CENTER);
    chrono.setEditable(false);
    chrono.setFont(new Font("Tahoma", Font.BOLD, 54));
    chrono.setText("");
    chrono.setBounds(631, 11, 127, 72);
    contentPane.add(chrono);
    chrono.setColumns(10);
  }
}

And my class B looks like this:

public class Actions extends Fenetre{
   ActionListener tache_timer;

    tache_timer = new ActionListener(){
        public void actionPerformed(ActionEvent e){
            sec++;
            String textRes = res.getText();
            if(sec == 3 ){
                res.setText("FAIL");

            }

            if(sec == 6){
                /*On realise une pause de 1 sec */
                try {
                    TimeUnit.SECONDS.sleep(1);
                } catch (InterruptedException e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                }

                EcouteClavier_actionPerformed(e);
                sec = 0;

            }
            chrono.setText("" + sec);// This JTextField is not working


        }
    };
}

The JTextField I am trying to use is called chrono. How can I use chrono from Class A to Class B

Answer 1

You have (at least) two chocies...

You could...

Pass a reference of the JTextField , either directly or indirectly via a reference of class A , to class B

This is generally not a good idea, as it starts to couple your code together in ways that make it difficult to change later as well as exposing elements of your code to uncontrollable change (once I have a reference to the text field, what's stopping me from removing it from it's parent container?)

You could...

Use a Observer Pattern to allow B to notify interested parties that some state has changed. This way B doesn't care who's interested or what they might want to do about the change, making it far more flexible and much easier to use and change in the future.

ActionListener is an example of an Observer Pattern , which notifies about some event which you need to take action on.

You could reuse any of the many EventListener s available in the core API or make your own. You'd then have A implement this listener (directly or indirectly) and register interest of notification with B . When B 's state changes, it would trigger an event notification back to the interested parties...

You shouldn't ...

Be tempted to use static !!