Select whole row in JTree

How do you make a tree node in a JTree stretch over the whole row? A TreeCellRenderer will not work since then the background will only appear to the right of the node. The answer is to use a TreeCellRenderer in combination with a TreeUI. Lets show how with an example.

Lets start of with a main class that creates a frame and adds a JTree.

import javax.swing.JFrame;
import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;


public class Main extends JFrame
{
  public Main()
  {
    DefaultMutableTreeNode root = new DefaultMutableTreeNode("Root");
    DefaultMutableTreeNode aa = new DefaultMutableTreeNode("Child AA");
    DefaultMutableTreeNode ab = new DefaultMutableTreeNode("Child AB");
    DefaultMutableTreeNode aba = new DefaultMutableTreeNode("Child ABA");
    DefaultMutableTreeNode abb = new DefaultMutableTreeNode("Child ABB");
    DefaultMutableTreeNode abba = new DefaultMutableTreeNode("Child ABBA");

    root.add(aa);
    root.add(ab);
    ab.add(aba);
    ab.add(abb);
    abb.add(abba);

    JTree tree = new MyTree(root);
    add(tree);

    pack();
    setVisible(true);
    setDefaultCloseOperation(EXIT_ON_CLOSE);
  }

  public static void main(String[] args)
  {
    new Main();
  }
}

Next, lets create a class that extend JTree.

import java.awt.Color;
import java.awt.Dimension;

import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;


public class MyTree extends JTree
{
  public MyTree(DefaultMutableTreeNode root)
  {
    super(root);

    setPreferredSize(new Dimension(200, 300));
    setRootVisible(false);
    setRowHeight(25);
    setBackground(Color.BLUE);
    setUI(new MyBasicTreeUI());
    setCellRenderer(new MyNodeRenderer());
  }
}

Then at last, we create the cell renderer and the tree UI.

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Component;
import java.awt.Dimension;

import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.TreeCellRenderer;


public class MyNodeRenderer implements TreeCellRenderer
{
  @Override
  public Component getTreeCellRendererComponent(JTree tree, Object value, boolean selected, boolean expanded, boolean leaf, int row, boolean hasFocus)
  {
    JPanel panel = new JPanel();
    if(selected)
    {
      panel.setBackground(Color.RED);
    }
    else
    {
      panel.setBackground(Color.BLUE);
    }

    panel.setLayout(new BorderLayout());

    panel.setPreferredSize(new Dimension(tree.getWidth(), tree.getRowHeight()));

    String text = (String)((DefaultMutableTreeNode)value).getUserObject();

    panel.add(new JLabel(text));

    return panel;
  }
}

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Insets;
import java.awt.Rectangle;

import javax.swing.Icon;
import javax.swing.JComponent;
import javax.swing.plaf.basic.BasicTreeUI;
import javax.swing.tree.TreePath;


public class MyBasicTreeUI extends BasicTreeUI
{
  @Override
  public Icon getExpandedIcon()
  {
    return null;
  }

  @Override
  public Icon getCollapsedIcon()
  {
    return null;
  }

  @Override
  protected void paintVerticalLine(Graphics g, JComponent c, int x, int top, int bottom)
  {}

  @Override
  protected void paintHorizontalLine(Graphics g, JComponent c, int y, int left, int right)
  {}

  @Override
  protected void paintRow(Graphics g, Rectangle clipBounds, Insets insets, Rectangle bounds, TreePath path, int row, boolean isExpanded, boolean hasBeenExpanded, boolean isLeaf)
  {
    if(tree.isRowSelected(row))
    {
      g.setColor(Color.RED);
      g.fillRect(0, row * tree.getRowHeight(), tree.getWidth(), tree.getRowHeight());
    }

    super.paintRow(g, clipBounds, insets, bounds, path, row, isExpanded, hasBeenExpanded, isLeaf);
  }
}

Actually, you don’t need to set the preferred size on the tree cell renderer panel. But doing so like in this case will make the whole panel clickable.

Select whole row in JTree

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