Question

I have a textfield in a class called RegPanel. I have instantiated my gui. I now need to find out if the field is empty when focus is lost, and if it is, I need to bring focus back to the textfield with a message “Please enter a name.”
So far I have tried `

 public void focusLost(FocusEvent e)
  {
     if(e.getSource()==gui.regPanel.regTextField.getText().trim().equals(""))
     {
        gui.regPanel.regTextField.setText("Please enter a name");
        gui.regPanel.regTextField.requestFocus();
     }         
     else gui.regPanel.regTextField.setText("");`

as well as I have tried variations on
if(e.getSource()==gui.regPanel.regTextField.getText().length()=0)
These are returning compile errors like ‘expected value found int, and ‘incomparable types:java.lang.Object and boolean.
I think I need to cast it to a string, but can’t figure out how.

Answer 1

In your if-statement you mixed up two comparisons in one. You want to test

1. is the source of the event my textfield
2. is my textfield empty

Therefore you have to make two checks and combine them with and:

e.getSource()==gui.regPanel.regTextField 
  && gui.regPanel.regTextField.getText().trim().equals("")

Remark: Your focus listener actually removes any text from your textfield if there is any (via the setText("")).