如何将ActionListener添加到动态创建的JButton中？

Question

I want to dynamically create a JFrame with a text field and two buttons. The problem is that JTextField is not visible inside the ActionListener of JButton ( treePanel.addObject(txt.getText()); ). How to solve this issue?

JButton addButton = new JButton("Add");
        addButton.setActionCommand(ADD_COMMAND);
        addButton.addActionListener(new ActionListener() 
        {
            @Override
            public void actionPerformed(ActionEvent event) 
            {
                JFrame f = new JFrame("Add new group/subgroup");
                JPanel p = new JPanel(new MigLayout());
                p.add(new JLabel("Group/subgroup name: "));
                JTextField txt = new JTextField(10);
                JButton ok = new JButton("Ok");
                JButton cancel = new JButton("Cancel");
                p.add(txt,"wrap");
                p.add(ok); 
                p.add(cancel);
                f.add(p);

                f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);                    
                f.pack();
                f.setLocationRelativeTo(null);
                f.setVisible(true);
                ok.addActionListener(new ActionListener() 
                {
                    @Override
                    public void actionPerformed(ActionEvent event)
                    {
                        treePanel.addObject(txt.getText()); 
                    }
                });
                cancel.addActionListener(new ActionListener() 
                {
                    @Override
                    public void actionPerformed(ActionEvent event)
                    {
                        f.dispose();    
                    }
                });
            }
        });

Answer 1

Anonymous classes is an inner classes and the strict rule applies to inner classes (JLS 8.1.3) :

Any local variable, formal method parameter or exception handler parameter used but not declared in an inner class must be declared final . Any local variable, used but not declared in an inner class must be definitely assigned before the body of the inner class .

So in your case you need to change the txt to be a final regarding the above rule.

final JTextField txt = new JTextField(10);