Java tree nodes from enum values

Question

I populate my JTree with nodes from enum values. But the nodes display in all uppercase text. This is undesirable as I would like the nodes to display in lower case.

example:

public enum DaysOfTheWeek {     


    MONDAY("Monday", "MON", "First day of the work week."), 
    //etc ...  

    private final String fullName;  
    private final String abbrvName;  
    private final String description;  

    DaysOfTheWeek(String fullName, String abbrvName, String description) {  
        this.fullName = fullName; 
        //etc ...  
    }  

    public String getFullName() {  
        return fullName;  
    }  
}

I have tried:

List<DefaultMutableTreeNode> daysOfWeekNodes = new ArrayList<>();  

for(DaysOfTheWeek dotw : DaysOfTheWeek.values()) {  

        daysOfWeekNodes.add(new DefaultMutableTreeNode(dotw.getFullName()));  
        daysOfWeekNodes.get(dotw.ordinal()).setUserObject(dotw);  
}

The node displays as: MONDAY But I want it to display as: Monday

text based graphic example:

Days  
    |  
    ---Monday  
    |  
    ---Tuesday

not

Days  
    |  
    ---MONDAY  
    |  
    ---TUESDAY

How do I get my tree node associated with the enum value, but its text on the tree to use the full name String? Or in other words, how to set a tree node user object but have its name different?

*note - an easy fix is to go against convention and name my values how I want them displayed in the tree, not all uppercase.

This code looks good. The problem is probably at the point of display, not at the point of tree creation. Can you post the display code? — durron597, May 03 '13 at 12:40
Don't really have any display code. I just add the tree to my panel after it is created. — CompSci-PVT, May 03 '13 at 13:15

Guillaume Polet · Accepted Answer · 2013-05-03T13:05:02.353

You need to use a TreeCellRenderer.

Here is one way to implement this:

import java.awt.Component;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.SwingUtilities;
import javax.swing.ToolTipManager;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeCellRenderer;
import javax.swing.tree.DefaultTreeModel;

public class TestTree {

    public enum DaysOfTheWeek {

        MONDAY("Monday", "MON", "First day of the work week."), TUESDAY("Tuesday", "TUE", "Second day of the work week");
        // etc ...

        private final String fullName;
        private final String abbrvName;
        private final String description;

        private DaysOfTheWeek(String fullName, String abbrvName, String description) {
            this.fullName = fullName;
            this.abbrvName = abbrvName;
            this.description = description;
        }

        public String getFullName() {
            return fullName;
        }

        public String getAbbrvName() {
            return abbrvName;
        }

        public String getDescription() {
            return description;
        }
    }

    public class MyTreeCellRenderer extends DefaultTreeCellRenderer {

        @Override
        public Component getTreeCellRendererComponent(JTree tree, Object value, boolean sel, boolean expanded, boolean leaf, int row,
                boolean hasFocus) {
            Component cell = super.getTreeCellRendererComponent(tree, value, sel, expanded, leaf, row, hasFocus);
            if (value instanceof DefaultMutableTreeNode && ((DefaultMutableTreeNode) value).getUserObject() instanceof DaysOfTheWeek) {
                ((JLabel) cell).setText(((DaysOfTheWeek) ((DefaultMutableTreeNode) value).getUserObject()).getFullName());
            }
            return cell;
        }
    }

    private JFrame f;
    private JTree tree;

    protected void initUI() {
        DefaultMutableTreeNode root = new DefaultMutableTreeNode("Days");
        for (DaysOfTheWeek dotw : DaysOfTheWeek.values()) {
            root.add(new DefaultMutableTreeNode(dotw));
        }
        final DefaultTreeModel model = new DefaultTreeModel(root);
        tree = new JTree(model);
        tree.setRootVisible(true);
        tree.setShowsRootHandles(true);
        ToolTipManager.sharedInstance().registerComponent(tree);
        tree.setCellRenderer(new MyTreeCellRenderer());
        f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setLocationRelativeTo(null);
        f.add(new JScrollPane(tree));
        f.pack();
        f.setVisible(true);
    }

    public static void main(String[] args) {

        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                new TestTree().initUI();
            }
        });
    }

}

Take a look at the JTree tutorial.

Wow, I was not expecting to have to craft a custom tree cell renderer in order to change the tree node text. — CompSci-PVT, May 03 '13 at 13:14
@JavaPVT you could also directly set the FullName of the days of the week as the user object of the DefaultMutableTreeNode but then you only manipulate `String` which is not really recommended. — Guillaume Polet, May 03 '13 at 13:18
I guess the really easy way would be to go against convention and just name my enum values not in uppercase. — CompSci-PVT, May 03 '13 at 13:21
@JavaPVT Not recommended: your UI should not depend on the way you coded. Actually, there is a simpler way but it is not recommended either. You could override the `toString()` method of your `enum` and return the "fullName". But `toString()` is only meant for developers, not for display. — Guillaume Polet, May 03 '13 at 13:23
@JavaPVT The clean and correct way to do what you want is to use a `TreeCellRenderer`, no doubt about that. I would really not recommend to change the name you gave to your enum constants. I would not recommend to override `toString()` either. People always start by saying, it was just to do a very small thing, quick & dirty, but eventually this gets into something bigger and bigger and you see odd bugs appear. — Guillaume Polet, May 03 '13 at 13:29

hamid · Answer 2 · 2013-05-03T12:53:54.950

0

Make a change here:

  List<DefaultMutableTreeNode> daysOfWeekNodes = new ArrayList<DefaultMutableTreeNode>();

Then try this:

  titleLabel.setText(node.getFullName());

edited May 03 '13 at 12:53

answered May 03 '13 at 12:47

hamid

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Unfortunately, it doesn't seem the node will type cast to my enum object. – CompSci-PVT May 03 '13 at 12:51
Actually, just realized, the label is not the problem. I want to the node text to display "Monday" not "MONDAY" which is how the enum value is typed in the class. – CompSci-PVT May 03 '13 at 12:59

Java tree nodes from enum values

2 Answers2