Java: How to programmatically select and expand multiple nodes in a JTree?

Question

I have a JTree and an awt.Canvas. When i select multiple objects from within the Canvas into the objList, I want all the selected items to be shown inside the JTree as selected. That means for example if I have 2 objects selected, both their paths to root should be expanded, and also each selected object should have its corresponding TreeNode selected. My JTree has TreeSelectionModel.DISCONTIGUOUS_TREE_SELECTION.

Here is a sample of the expand funcion i use :

public void selectTreeNodes() {


    HashMap <String, MyEntity> entities = ...;
    Iterator it = entities.keySet().iterator();
    while (it.hasNext()) {

        String str = it.next().toString();
        MyEntity ent = entities.get(str);

        if (ent.isSelected()) {
            DefaultMutableTreeNode searchNode = searchNode(ent.getName());
            if (searchNode != null) {

                TreeNode[] nodes = ((DefaultTreeModel) tree.getModel()).getPathToRoot(searchNode);
                TreePath tpath = new TreePath(nodes);
                tree.scrollPathToVisible(tpath);
                tree.setSelectionPath(tpath);
            }
        }
    }
}

public DefaultMutableTreeNode searchNode(String nodeStr) 
{ 
    DefaultMutableTreeNode node = null; 

    Enumeration enumeration= root.breadthFirstEnumeration(); 
    while(enumeration.hasMoreElements()) {

        node = (DefaultMutableTreeNode)enumeration.nextElement(); 
        if(nodeStr.equals(node.getUserObject().toString())) {

            return node;                          
        } 
    } 

    //tree node with string node found return null 
    return null; 
}

In my current state, if I select a single object, it will be selected in the JTree and its TreePath will be shown. But if entities has more than 1 object selected, it will display nothing, my JTree will remain unchanged.

*"I have a `JTree` and an `awt.Canvas`."* Don't mix Swing with AWT components. The `Canvas` should be a `JPanel` or an image displayed in a `JLabel`. — Andrew Thompson, Apr 20 '12 at 10:03
I know I shouldn't usually do that (I have some problems with the main menu expanding behind the canvas), but in this case the only connection between them is the array of entities from the canvas that are represented in the tree. And in the GUI there is some space between them, so no harm is done/ — Pantaziu Cristian, Apr 20 '12 at 11:58

score 20 · Accepted Answer · answered Apr 20 '12 at 09:15

You are looking for the TreeSelectionModel of the JTree (use the getter). Use the TreeSelectionModel#setSelectionPaths for multiple paths. Now you are only setting one node selected due to your tree.setSelectionPath(tpath); call. The TreeSelectionModel also has methods to add/remove to an existing selection ,... (basically everything you might need in the future).

An interesting method for the expansion is the JTree#setExpandsSelectedPaths method which allows to configure the JTree to automatically expand selected paths. If you want to manage this manually, you can use the JTree#setExpandedState method

Thank you. I was stuck on this for months. – null Dec 25 '14 at 08:01 — null, Dec 25 '14 at 08:01

Java: How to programmatically select and expand multiple nodes in a JTree?

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