title: JPopupPanel closed when click on its JPopupMenu
body: <p>I have a <code>JPopupPanel</code> showing up when a button is clicked.</p>
  
  <p>This <code>JPopupPanel</code> has a <code>JPopupMenu</code> which shows up with the mouse right click, showing different options. 
  When left button pressed to choose one of this options in the PopupMenu, the PopupPanel closes leaving the PopupMenu by itself for a moment, and when the button is released, the PopupMenu also dissapears (as expected), but the action cannot be seen in the PopupPanel since it is already closed.</p>
  
  <p>How can I avoid the JPopupPanel to close when choosing one of the options of the JPopupMenu?</p>
  
  <p>Thanks</p>