Trivial program flickers on startup.

Question

The following program flickers on startup - the field is sometimes displayed, then erased, then displayed again.
From the output to the error stream, it appears that the field is being painted, before the frame has even been. It's not surprising then that it gets erased when the frame is painted for the first time. This happens after the frame is made visible.
Indeed. I've got around it with a hack which consists of having JTextField's paint method ignore the request if the frame hasn't been painted.
But why does this happen?
import javax.swing.*;
import java.awt.Container;
import java.awt.Graphics;
public class Flicker implements Runnable {
     public static void main(String args[]) {
          SwingUtilities.invokeLater(new Flicker());
     public void run() {
          JFrame jf = new MyFrame();
          jf.setSize(800, 800);
          Container jfcp = jf.getContentPane();
          jfcp.setLayout(null);
          JComponent jtf = new MyTextField();
          jtf.setLocation(500, 500);
          jtf.setSize(jtf.getPreferredSize());
          jfcp.add(jtf);
          jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          System.err.println("Setting frame visible");
          jf.setVisible(true);
     class MyTextField extends JTextField {
          @Override
          public void paint(Graphics g) {
               System.err.println("JTextField paint called");
               super.paint(g);
          MyTextField() {
               super("Field text");
     class MyFrame extends JFrame {
          public void paint(Graphics g) {
               System.err.println("JFrame paint called");
               super.paint(g);
          public void update(Graphics g) {
               System.err.println("JFrame update called");
               super.update(g);
}

Answer 1

OK, FWIW, what I've surmised is this. When the JFrame is set visible, a PaintEvent is posted to the event queue. Then, when the swing component's repaint methods are called, the RepaintManager posts an InvocationEvent to run some code that will call the components' paint(Graphics) methods.
The problem is that InvocationEvent events have a higher priority than PaintEvent events, so when the code constructing the component graph completes, the first event that gets dispatched is the one for the RepaintManager, which accordingly paints the components. Then finally the paint event is dispatched, and the frame paints itself and its children.
A workaround, of sorts, is to set the frame visible as soon as it has been constructed and had its size and position set, and then to defer the rest of the code to a point after the PaintEvent is dispatched. This can be done using an AwtEventListener, as shown below. The major downside is that adding such a listener may be prevented by a SecurityManager.
It becomes more fun when a layout manager is used for the frame, because it cannot be sized until all its descendant components have been added. The best I can think of is to add them all, pack the frame, then remove them again (or just their common ancestor), set the frame visible, and again wait for the paint event before adding them back.
I can only assume that everyone out there is using such fast machines that the flicker is not visible.
Sylvia.
import javax.swing.*;
import java.awt.AWTEvent;
import java.awt.Container;
import java.awt.Graphics;
import java.awt.Toolkit;
import java.awt.Component;
import java.awt.event.AWTEventListener;
import java.awt.event.PaintEvent;
public class Flicker implements Runnable {
     public static void main(String args[]) {
          SwingUtilities.invokeLater(new Flicker());
     public void run() {
          final JFrame jf = new MyFrame();
          jf.setSize(800, 800);
          jf.setVisible(true);
          new MyAwtEventListener(jf, new Runnable() {
               public void run() {
                    secondPart(jf);
     private void secondPart(JFrame jf) {
          Container jfcp = jf.getContentPane();
          jfcp.setLayout(null);
          JComponent jtf = new MyTextField();
          jtf.setLocation(500, 500);
          jtf.setSize(jtf.getPreferredSize());
          jfcp.add(jtf);
          jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          System.err.println("Setting frame visible");
          jf.setVisible(true);
     static class MyAwtEventListener implements AWTEventListener {
          private final Runnable runnable;
          private final Component component;
          MyAwtEventListener(Component component, Runnable runnable) {
               this.runnable = runnable;
               this.component = component;
               Toolkit.getDefaultToolkit().addAWTEventListener(this, PaintEvent.PAINT_EVENT_MASK);
          public void eventDispatched(AWTEvent event) {
               if(event.getID() == PaintEvent.PAINT && event.getSource() == component) {
                    Toolkit.getDefaultToolkit().removeAWTEventListener(this);
                    SwingUtilities.invokeLater(runnable);
     class MyTextField extends JTextField {
          @Override
          public void paint(Graphics g) {
               System.err.println("JTextField paint called");
               super.paint(g);
          MyTextField() {
               super("Field text");
     class MyFrame extends JFrame {
          public void paint(Graphics g) {
               System.err.println("JFrame paint called");
          public void update(Graphics g) {
               System.err.println("JFrame update called");
               super.update(g);
}