JTree set background of node to non-opaque

Question

Please have a look at the SSCCE. How can I make the non-selected tree nodes\' background transparent. At the moment the background of non-selected nodes is white. My cell re

Answer 1

You should override getBackgroundNonSelectionColor,getBackgroundSelectionColor and getBackground of DefaultTreeCellRenderer and return appropriate values like so:

public class MyCellRenderer extends DefaultTreeCellRenderer {

    @Override
    public Color getBackgroundNonSelectionColor() {
        return (null);
    }

    @Override
    public Color getBackgroundSelectionColor() {
        return Color.GREEN;
    }

    @Override
    public Color getBackground() {
        return (null);
    }

    @Override
    public Component getTreeCellRendererComponent(final JTree tree, final Object value, final boolean sel, final boolean expanded, final boolean leaf, final int row, final boolean hasFocus) {
        final Component ret = super.getTreeCellRendererComponent(tree, value, sel, expanded, leaf, row, hasFocus);

        final DefaultMutableTreeNode node = ((DefaultMutableTreeNode) (value));
        this.setText(value.toString());
        return ret;
    }
}

which will produce:

Other suggestions:

• Create and manipulate Swing components on Event Dispatch Thread.
• Dont extend JFrame unnecessarily rather create an instance and use that.
• Dont call setSize on JFrame rather use a correct LayoutManager and/or override getPreferredSize() and call pack() on JFrame before setting it visible but after adding all components.
• Remember to call JFrame#setDefaultCloseOperation with either DISPOSE_ON_CLOSE or EXIT_ON_CLOSE (DISPOSE_XXX is usually preferred unless using Timers as this will allow main(String[] args) to continue its execution after Gui has been closed).

Answer 2

To avoid background refilling, just put UIManager.put("Tree.rendererFillBackground", false); before new SimpleTree(); or after super("Creating a Simple JTree");.