HELP: JPanel NOT shown

Question

hi,
I have a simple program: one frame's content pane adds two JPanels.
Source as follows:
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class DragTest2 {
public static void main(String[] args) {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setSize(new Dimension(Constants.RECEIPT_WIDTH_X_AXIS,
(int)(Constants.RECEIPT_WIDTH_X_AXIS/Constants.RECEIPT_X_WIDTH_TO_Y_LENGTH_RATIO)));
Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
int x = screenSize.width/2 - frame.getSize().width/2;
int y = screenSize.height/2 - frame.getSize().height/2;
frame.setLocation(x, y);
Container c = frame.getContentPane();
c.setLayout(null);
// Adding two panels
c.add(new DraggableJPanel(100, 200));
c.add(new DraggableJPanel(300, 400));
c.validate();
Insets insets = frame.getInsets();
frame.setVisible(true);
public class DraggableJPanel extends JPanel {
private final JPanel p;
private final JTextField tf;
public DraggableJPanel(int x, int y){
tf = new JTextField(Integer.toString(x)+"---"+Integer.toString(y));
p = this;
tf.addMouseMotionListener(new MouseMotionAdapter() {
public void mouseDragged(MouseEvent e) {
p.setLocation(p.getX()+e.getX(), p.getY()+e.getY());
this.add(tf);
p.setLocation(x,y);
Nothing fancy here.
However, when i run the program, i can NOT see any jtextfield. Moreover, if I comment out
the c.setLayout(null), I can see the 2nd Jtextfield (but in a wrong location, not 300, 400),
not the first.
Any help is greatly appreciated.
JK

Answer 1

BorderLayout is the default layout for a contentpane. By default, add() adds a componetn to the center of
the border layout. You can only have one component
in the center. If you put another there, the first
is gone. Either use add(myPanel, BorderLayout.NORTH)
or change the layout.Thanks for the help.
I want to do the absolute positioning, that is why inside DraggableJPanel, I have setLocation( ) called:
this.setLocation(x,y);
However, for some reason, the JPanel doesn't show up at all.
Seems to me content pane is ignoring this setLocation call for some reason.
You pointed out a good diretion, i will continue investigate. Thanks again.
JK