Q:

Make JSplitPane fully transparent

I am writing GUI program in Java. 
I have a JPanel called jpanel1 that I inserted a JSplitpane (jSplitPane1) on it. I set right and left components of jSplitPane1; jpanel2 & jpanel3. I set a background image on downward panel (jpanel1) and I want to JSplitPane and it's right and left components be transparent such that I can see the background image on them. Is this possible in Java?  If this is possible can I use that method to transparent JTree as JSplitpane?

A:

It depends on the L&F. AquaL&F on MacOS will respect setOpaque(false) but e.g. Nimbus does not seem to care about it. To force a transparent divider you need to override it in the UI definition of the JSplitPane
 jSplitPane.setUI(new BasicSplitPaneUI(){
            @Override
            public BasicSplitPaneDivider createDefaultDivider() {
                return new BasicSplitPaneDivider(this){
                    @Override
                    public void paint(Graphics g) {
                    }
                };
            }
        });

A potential disadvantage is that this approach overrides the L&F for this component and thus might take away other L&F theming elements.

