Re: I need a different approach - suggestions please
On 27/06/2012 6:21 PM, Patricia Shanahan wrote:
On 6/27/2012 2:44 PM, bilsch wrote:
...
The listeners all call a statement in the second file:
public void actionPerformed(ActionEvent event)
so I don't understand how a button listener can be different from
another button listener.
You can write several different implementing classes for an interface
such as ActionListener. You can then create different instances of the
same implementing class.
For example, you could have a NumberKeyListener class that implements
ActionListener, and takes a constructor parameter that tells it the
value associated with its button. On the other hand, I would have a
different class for dealing with backspace.
Code like:
one.addActionListener(new NumberKeyListener(1));
two.addActionListener(new NumberKeyListener(2));
would get rid of a lot of checking which button was pressed.
Another option uses the ActionEvent the listener gets passed, a
parameter that's frequently ignored:
public void actionPerformed (ActionEvent e) {
JButton btn = (JButton)(e.getSource());
String btnTxt = btn.getText();
// btnTxt should be "0", "1", ..., or "9".
// Do something with it.
}
Of course, this action listener will blow up if used on something other
than a JButton. You also might not like the results if you later
localize the button labels using a ResourceBundle or something. :) In
the event that that sort of thing is likely, the numeric-parameter
approach Patricia suggested is more robust. Another possibility is:
private static Map<JButton,Integer> buttonMap;
....
for (int i = 0; i < 10; i++) {
JButton btn = new JButton("" + i);
btn.addActionListener(new NumberKeyListener());
buttonMap.add(btn,i);
}
....
public void actionPerformed (ActionEvent e) {
int btnNum = buttonMap.get(e.getSource());
}
Note: will throw NPE if attached to something other than a button that's
in buttonMap. Also, for buttonMap to be visible in actionPerformed,
NumberKeyListener needs to be a nested class of the class with the rest
of this code.