Creating a class that extends keyListener

Question

In my java project, I want to check the input in each JTextField in a few different classes (with the exact same code)..

Right now I have the same code copied over and over and I was suggested with 2 options:

1. Create a method and call the method instead.

2. Create a new class that extends from another class (I don't know which yet) that has the method needed.

The code I'm using now is:

totalAmount.addKeyListener(new KeyAdapter() {
@Override
    public void keyTyped(KeyEvent arg0) {
    //do something
    }
});

And the new class is:

public class Listener extends KeyAdapter {
    public void keyTyped(KeyEvent arg0){
    //do something
    }
}

The problem is that I don't know if I'm extending the right class, and how to use the new class I've written...

Thanks in advance!

Answer 1

To do what you are wanting with your key adapter you would use

totalAmount.addKeyListener(new Listener());

and your code of your key adapter is correct.

public class Listener extends KeyAdapter {
    public void keyTyped(KeyEvent arg0){
        //do something
    }
}

To get the text from a JTextField you could either use this code inside your keyAdapter

System.out.println(totalAmount);

or, preferably you could use a document listener. This would be done by

public class documentListener implements DocumentListener //This is a listener
{
    public void changedUpdate(DocumentEvent e){

    }

    public void removeUpdate(DocumentEvent e){
        int lengthMe = e.getDocument().getLength();
        System.out.println(e.getDocument().getText(0,lengthMe));
    }

    public void insertUpdate(DocumentEvent e){
        int lengthMe = e.getDocument().getLength();
        System.out.println(e.getDocument().getText(0,lengthMe));
    }
}

and it would be added to the JTextField with

totalAmount.getDocument().addDocumentListener(new documentListener());