code: public void closeWindowPerformed(SwingFrame frameView) {
  		if (!navigationFrames.contains(frameView)) return;
  		
  		if (navigationFrames.size() == 1 && !askBeforeExit(frameView)) {
  			return;
  		}
  		
  		if (frameView.tryToCloseWindow()) {
  			removeNavigationFrameView(frameView);
  		}
  	}
docs: Asks the use about closing and then tries to close the Window
  
  @param frameView NavigationFrameView to close