Why my textfield can not get focus?

Question

I put a textfield on the first tab of a tabbed panel. I need this textfield to get the focus when I open the first tab. I tried to use grabfocus() method in the constructor of class, but it does not work. Does anybody know why? and how can I solve it?
Thanks!

Answer 1

No, I didn't call grab/requestFocus on the event thread.
My code is like this:
public class GeneralPane extends JPanel {
JPanel ltPane;
private JTextField txtCountry;
public GeneralPane() {
initComponents();
private void initComponents(){
setLayout(new BorderLayout());
//Add another Panel to contain Labels and Text fileds
ltPane = new JPanel();
FocusListener mFL = new FL();
txtCountry = new JTextField("US", 20);
//this listener is used to store the data in the textfield into a variable
txtCountry.addFocusListener(mFL);
// add the textfield into ltPane
mUtil.insertTextPane(txtCountry,ltPane);
//txtCountry got focus
//txtCountry.setFocusable(true);
ltPane.requestFocus();
//txtCountry.requestFocusInWindow();
Then in the main program, I create an instance of this class and then use addTab(...) function into the my tabbedPanel.
The logic is simple, but the textfield still couldn't get focus when I open the tabbedPanel.