Highlight tree node

Question

A quick problem for you experts. I am trying to get a node in a JTree to be highlighted with the 'blue' background as if someone has selected it with a mouse click. Unfortunately, setSelectionPath(TreePath path) is not doing this for me.
I am using a custom TreeCellRenderer which extends the DefaultTreeCellRenderer. Would anyone know what exactly I need to do in my custom renderer to highlight a node?
thanks.

Answer 1

Good time for asking your question 'cause I just had a similar problem and finally figured out how to fix it.
First, the DefaultTreeCellRenderer has a few variables that determine the text color, background color, selection text color, selection background color, etc. The ones you want to modify to make selection work would be: backgroundSelectionColor and maybe textSelectionColor.
Another variable is protected boolean selected, if it's true then your node should be highlighted.
If you look at the DefaultTreeCellRenderer's Constructor it is:
  public DefaultTreeCellRenderer() {
    setHorizontalAlignment(JLabel.LEFT);
    setLeafIcon(UIManager.getIcon("Tree.leafIcon"));
    setClosedIcon(UIManager.getIcon("Tree.closedIcon"));
    setOpenIcon(UIManager.getIcon("Tree.openIcon"));
    setTextSelectionColor(UIManager.getColor("Tree.selectionForeground"));
    setTextNonSelectionColor(UIManager.getColor("Tree.textForeground"));
    setBackgroundSelectionColor(UIManager.getColor("Tree.selectionBackground"));
    setBackgroundNonSelectionColor(UIManager.getColor("Tree.textBackground"));
    setBorderSelectionColor(UIManager.getColor("Tree.selectionBorderColor"));
    Object value = UIManager.get("Tree.drawsFocusBorderAroundIcon");
    drawsFocusBorderAroundIcon = (value != null && ((Boolean)value).
                          booleanValue());
    }All it's doing here is gathering the colors specified by your UIManager and storing them in as textSelectionColor, backgroundSelectionColor, etc.
If you want to use the colors define in your UIManager you don't need to call anything, however if you want to set a certain backgroundSelectionColor like blue, you would call setBackgroundSelectionColor(Color.BLUE) in your constructor (instead of what is up there)...All the constructor does is just store these colors in the DefaultTreeCellRenderer's variables, it does not select or color anything just yet.
Basically if you want something to be shown as selected you have to look at this function: getTreeCellRendererComponent(JTree tree, Object value, boolean sel, boolean expanded, boolean leaf, int row, boolean hasFocus) In my code I made a custom TreeUI which extends BasicTreeUI and in it I override the    protected void paintRow(Graphics g, Rectangle clipBounds, Insets insets, Rectangle bounds, TreePath path, int row, boolean isExpanded, boolean hasBeenExpanded, boolean isLeaf) function of BasicTreeUI and if the TreePath that is being passed to it is the one I want highlighted I see that the real highlighting occurs when it calls DefaultTreeCellRenderer.getTreeCellRendererComponent()... basically you pass in your JTree, then the node path.getLastPathComponent() that you are currently wanting to paint, then sel (which is set to true if you want that node selected), then expanded (if you want it expanded), leaf (if you want it drawn as a leaf), row (the row that the node resides), and hasFocus (if you've allowed a focus Listener). This function returns to you a Component which you paint using paintComponent - the code for paintRow() is all in BasicTreeUI.java.
Even though I did all that, all you need to do, if you are calling your custom TreeCellRenderer from you MouseHandler or Listener is setForeground(), the DefaultTreeCellRenderer renders a selected node by calling setForeground(getTextSelectionColor()) and it renders an unselected node by calling setForeground(getTextNonSelectionColor()), it also sets selection (boolean) value to true if your node is supposed to be selected - those things are all done when getTreeCellRendererComponent is called. When paint() is called the node is actually drawn as being selected.
so in short:
setTextSelectionColor(Color.WHITE);
setBackgroundSelectionColor(Color.BLUE);
setForeground(getTextSelectionColor());  //from getTreeCellRendererComponent();
selection = true;
paint(Graphics g);Those are the functions you should look at and hopefully you can get your node highlighted.