Initial Focus

Question

I have six text boxes in a panel. How do I make the initial focus to be in the first enabled text box. And how do I make the focus to traverse in a serial order..like how it used to work with setNextFocusableComponent() in jdk1.3.
Please help.

Answer 1

Here you are (It's Christmas time ;-) )
The following programme demonstrates a simple way of controlling the focus
sequence when navigating with the TAB and shift-TAB keys through the components
of a panel.
Here we have only four textfields (tf1-tf4) in one column and two buttons (b1,
b2) in a second column. When running the programme, the focus sequence is: tf1,
b1, tf2, tf3, b2, tf4.
But this is not really what we would like. We'd rather prefer to first fill the
textfields and then choose between two different actions. So remove the comment
slashes in
//    panel.setFocusCycleRoot(true);
//    panel.setFocusTraversalPolicy(new MyFocusTraversalPolicy());
Recompile and run, and see that the sequence is now: tf1, tf2, tf3, tf4, b1, b2
as desired.
What has happened?
With "panel.setFocusCycleRoot(true);" we declared our panel as the FocusCycleRoot
which is an obligatory step. The actual FocusTraversalPolicy is defined in our
own class MyFocusTraversalPolicy. What happens there? Not very much. The
important thing is that it extends ContainerOrderFocusTraversalPolicy; read well
the word "ContainerOrder..." that means the order is taken from our panel IN THE
SEQUENCE WE ADDED OUR COMPONENTS THERE. Make a brief test in changing the order
in the panel: Cut the line
    panel.add(tf4);
and paste it after
    panel.add(b2);
Compile and run. Yes, our sequence has changed to: tf1, tf2, tf3, b1, b2, tf4.
Remains to explain the effect of the method "protected boolean accept(Component
aComp)" in class MyFocusTraversalPolicy. Well, without the accept-method the
focus would move in our example also to the JLabels and the JPanel itself. So the
method makes sure that the focus rests only on components which can accept input
or fire an action.
import java.awt.*;
import javax.swing.*;
public class FocusSeqDemo
  public static void main(String args[])
  { new FocusSeqDemo();
  public FocusSeqDemo()
  { JFrame frame = new JFrame();
    frame.setSize (210,220);
    frame.setTitle ("FocusSeqDemo");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    Container cp = frame.getContentPane();     
    JPanel panel = new JPanel();
    panel.setLayout(null);
//    panel.setFocusCycleRoot(true);
//    panel.setFocusTraversalPolicy(new MyFocusTraversalPolicy());
    JLabel l1= new JLabel("A:");
    JLabel l2= new JLabel("B:");
    JTextField tf1= new JTextField();
    JTextField tf2= new JTextField();
    JTextField tf3= new JTextField();
    JTextField tf4= new JTextField();
    JButton b1 = new JButton("action 1");
    JButton b2 = new JButton("action 2");
    Insets insets= new Insets(0,0,0,0);
    b1.setMargin(insets);
    b2.setMargin(insets);
    l1.setBounds(10,40,20,21);
    l2.setBounds(10,100,20,21);
    tf1.setBounds(30,40,50,21);
    tf2.setBounds(30,70,50,21);
    tf3.setBounds(30,100,50,21);
    tf4.setBounds(30,130,50,21);
    b1.setBounds(110,60,60,30);
    b2.setBounds(110,100,60,30);
    panel.add(l1);
    panel.add(l2);
    panel.add(tf1);
    panel.add(tf2);
    panel.add(tf3);
    panel.add(tf4);
    panel.add(b1);
    panel.add(b2);
    cp.add(panel, BorderLayout.CENTER);
    frame.setVisible(true);
    panel.getComponent(2).requestFocusInWindow(); // component 0 and 1 are the
//                                             labels.
  class MyFocusTraversalPolicy extends ContainerOrderFocusTraversalPolicy
  { protected boolean accept(Component aComp)
    { if (aComp instanceof JTextField || aComp instanceof JButton)
                              return super.accept(aComp);
      return false; // JLabel and JPanel.
}