Pass arguments into JButton ActionListener

Question

I'm looking for a way to pass a variable or string or anything into an anonymous actionlistener ( or explicit actionlistener ) for a JButton. Here is what I have:

public class Tool {
...
  public static void addDialog() {
    JButton addButton = new JButton( "Add" );
    JTextField entry = new JTextField( "Entry Text", 20 );
    ...
    addButton.addActionListener( new ActionListener( ) {
      public void actionPerformed( ActionEvent e )
      {
        System.out.println( entry.getText() );
      }
    });
  ...
  }
}

Right now I just declare entry to be a global variable, but I hate that way of making this work. Is there a better alternative?

Solution 1

1. Create a class that implements the ActionListener interface.
2. Provide a constructor that has a JTextField argument.

---

Example -

class Foo implements ActionListener{
    private final JTextField textField;

    Foo(final JTextField textField){
        super();
        this.textField = textField;
    }
    .
    .
    .
}

---

Problem?

Solution 2

2 ways

1. make entry final so it can be accessed in the anonymous class

   public static void addDialog() {
       JButton addButton = new JButton( "Add" );
       final JTextField entry = new JTextField( "Entry Text", 20 );
       ...
       addButton.addActionListener( new ActionListener( ) {
         public void actionPerformed( ActionEvent e )
         {
           System.out.println( entry.getText() );
         }
       });
     ...
     }
   

2. make entry a field

   JTextField entry;
   public static void addDialog() {
       JButton addButton = new JButton( "Add" );
       entry = new JTextField( "Entry Text", 20 );
       ...
       addButton.addActionListener( new ActionListener( ) {
         public void actionPerformed( ActionEvent e )
         {
           System.out.println( entry.getText() );
         }
       });
     ...
     }
   

Solution 3

Maybe better in this case to use Action and AbstractAction, where you could do that kind of thing.

Solution 4

From the code I see here, entry is NOT a global variable. It's a local variable in the addDialog() method.. Did I misunderstand you?

If you declare the variable locally as final, then the listener will be able to access it.

    final JTextField entry = new JTextField( "Entry Text", 20 );
    ...
    addButton.addActionListener( new ActionListener( ) {
      public void actionPerformed( ActionEvent e )
      {
        System.out.println( entry.getText() );
      }
    });
  ...

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