JTextField.focusLost is called multiple times. Why?
I have a JTextField component called projectNum.
On focusLost I'm trying to prevent user to leave an empty field.
But I have a problem, because focusLost is called two times.
Here is a code snippet:
projectNum.addFocusListener(new FocusAdapter(){
publicvoid focusGained(FocusEvent e){}
publicvoid focusLost(java.awt.event.FocusEvent e){
if(!e.isTemporary()){//only for permanent lost of focus
if (validProjectNum()){
newProject.setProjectNum(Integer.valueOf(projectNum.getText().trim()).intValue());
}else{
if(!projectNum.hasFocus()){
projectNum.requestFocus();
}
}
}
}
}
});
Method "validProjectNum()" simply checks if JTextField is empty and
if so, shows JOptionPane message and returns false.
Problem is that I'm geting that message twice
(four times if I exclude: if(!e.isTemporary()) ).
I can't figure out who is calling focusLost the second time.
How can I prevent it to be called only once.
I appreciate any help or hint.
Thanks.
[1830 byte] By [
Toxtera] at [2007-10-2 10:22:44]
> Use an InputVerifier instead of handling the
> focusLost() event.
Well, I've tried that allready but It doesn't work.
JOptionPane.showMessageDialog is never called.
Here is a code snippet from it:class MyVerifier extends InputVerifier {
public boolean verify(JComponent input){
return validProjectNum();
}
}
projectNum.setInputVerifier(new MyVerifier());
> > class MyVerifier extends InputVerifier
> {
>public boolean verify(JComponent input)
>{
>JTextField tf = (JTextField)input;
>if(tf.getText().equals("") return false;
>return true;
>}
> }
>
OK, but where to show a message to a user?
This only prevents user from leaving a field if is empty.
Thanks.
> > OK, but where to show a message to a user?
>
> if the textfield is empty, this line executes
> if(tf.getText().equals("")) return false;
>
> perhaps you could add your message as part of the
> 'block' of this if statement
Well, I've tried that allready (see my second post, method validProjectNum()
does exactly that).
Anyway, I solved the problem using focusLost and a little trick:jTextField.requestFocus();
jTextField.setFocusable(false);
JOptionPane.showMessageDialog(null, "error message");
jTextField.setFocusable(true);
jTextField.requestFocus();
So as you can see, key thing is to temporary disable focus on component
and than enable it back after JOptionPane.showMessageDialog().
It looks like JOptionPane.showMessageDialog()
triggers focusLost() event.
Thanks everyone.
also works like this
class MyVerifier extends InputVerifier
{
public boolean verify(JComponent input)
{
JTextField tf = (JTextField)input;
if(tf.getText().equals(""))
{
input.setInputVerifier(null);
JOptionPane.showMessageDialog(null,"Error, textfield empty");
input.setInputVerifier(this);
return false;
}
return true;
}
}
> also works like this
>
> ...
>input.setInputVerifier(null);
>JOptionPane.showMessageDialog(null,"Error, "Error, textfield empty");
>input.setInputVerifier(this);
...
>
That did the trick!
I like this more than manipulating with focusLost and focusGained.
This is much more elegant solution, because focus is never lost from this
component (unlike focusLost which reacts after component lost its focus).
Thank you very much!
