Translucent JFrame repaint

• download example.jar
• download src.zip
• repository

Code

DateTimeFormatter formatter = DateTimeFormatter.ofPattern("HH:mm:ss");
JLabel label = new JLabel(LocalTime.now().format(formatter), SwingConstants.CENTER);
Timer timer = new Timer(100, null);
timer.addActionListener(e -> {
  label.setText(LocalTime.now().format(formatter));
  Container parent = SwingUtilities.getUnwrappedParent(label);
  if (Objects.nonNull(parent) && parent.isOpaque()) {
    repaintWindowAncestor(label);
  }
});
// ...
private void repaintWindowAncestor(JComponent c) {
  JRootPane root = c.getRootPane();
  if (root == null) {
    return;
  }
  Rectangle r = SwingUtilities.convertRectangle(c, c.getBounds(), root);
  root.repaint(r.x, r.y, r.width, r.height);
}

References

• Translucent JFrame repaint(Japanese)