If the searchSupplier frame is already on the desktop, it is unlikely that you will able to add it again. Try using getParent
to determine if the frame needs to be added
if (searchSupplier.getParent() == null) {
Main.getInstance().getPortada().getDesktop().add(searchSupplier);
}
searchSupplier.setVisible(true);
Main.getInstance().getPortada().getDesktop().moveToFront(searchSupplier);
try {
searchSupplier.setSelected(true);
} catch (PropertyVetoException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}