更改JButton的文字或颜色而没有最终的？

Question

Hey all I can change the text of 1 single button easily with "final" but I need to create lots of buttons for a flight booking system, and when the buttons are more, final doesnt work ...

JButton btnBookFlight;

eco = new EconomyClass();
eco.setSeats(5);
for(int i=0;i<20;i++){
    btnBookFlight = new JButton("Book" +i);
    btnBookFlight.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent arg0) {
            btnBookFlight.setBackground(Color.RED);
            btnBookFlight.setOpaque(true);
            btnBookFlight.setText("Clicked");
        }
    });
    btnBookFlight.setBounds(77, 351, 100, 23);
    contentPane.add(btnBookFlight);
} 

I would be glad if you can suggest me any trick to get over this.I want to change a buttons color or text when it is clicked or maybe some other cool effects when mouse over but for now only text or color will be enough =).Thanks for your time!

Answer 1

Use the source of the ActionEvent in the ActionListener

btnBookFlight.addActionListener(new ActionListener() {
    @Override
    public void actionPerformed(ActionEvent event) {

      JButton button = (JButton)event.getSource();
      button.setBackground(Color.RED);
      ...
    }
});

btnBookFlight has to be final for the inner class ( ActionListener ) to access it.

From JLS 8.1.3

Any local variable, formal parameter, or exception parameter used but not declared in an inner class must be declared final.

If this is not permitted, then the JButton may be accessed using the source component of the ActionEvent itself using getSource .

However, that said, the simplest solution would be to move the JButton declaration within the scope of the for loop and make it final :

for (int i = 0; i < 20; i++) {
    final JButton btnBookFlight = new JButton("Book" + i);
    btnBookFlight.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent arg0) {
            btnBookFlight.setBackground(Color.RED);
            ...
        }
    });
}

Answer 2

Just avoid using anonymous classes for your action listener and the final constraint will disappear.

What I mean is use:

class MyActionListener implements ActionListener {
  public void actionPerformed(ActionEvent e) {
    JButton src = (JButton)e.getSource();
    // do what you want

  }
}