Plugins + Scripts CustomTreeUI

{
    CustomTreeUI<String>tree = new CustomTreeUI<String>(this, "TreeBasic")
        .newHalfLineUI(CreateUIElement, true).setHeight(330)
        .setColorSet(CustomTreeUI<String>.UI_SKIN_BASIC)
        .addSelectClickCallback(selectClickEvent)
        .addDoubleClickCallback(doubleClickEvent)
        .addExpandClickCallback(expandClickEvent);
    setdata(tree);
}

public static void setdata(CustomTreeUI<String>tree)
{
    tree.removeAll();
    TreeItem<String>item1 = tree.add("Fruit");
    item1.add("Apple");
    item1.add("Banana");
    item1.add("Grape");
    item1.add("Pineapple");

    TreeItem<String>item2 = tree.add("Car");
    TreeItem<String>item2sub1 = item2.add("Sedan");
    TreeItem<String>item2sub2 = item2.add("Trucks");

    item2sub1.add("Hyundai");
    item2sub1.add("Chevrolet");
    item2sub1.add("Toyota");
    item2sub1.add("Jaguar");
    item2sub1.add("Tesla");

    item2.find("Trucks").add("Ford");
    item2.find("Trucks").add("Chevrolet");
    item2.find("Trucks").add("GMC");
    item2.find("Trucks").add("RAM");
}

// Defined binding structure
public class TreeSystem : TreeItem<Tree>
{// sup_tree : parent(super) treeitem
 // this_obj : thiz object,  you want to handle will be this
 // tree_dep : depth of the hierarchical structure
    public TreeSystem(TreeItem<Tree>sup_tree, Tree this_obj, int tree_dep = 0)  : base(sup_tree, this_obj, tree_dep) {}
    public override String getName(Tree o)
    {
        return o.nme;
    }

    public override String getDisplayName(Tree o)
    {
        return getName(o);
    }

    public override String getPath(TreeItem<Tree>sup_tree, Tree o)
    {
        String sup_path = is_root() ? "/" : sup_tree.treepath + "/";
        return sup_path + getName(o);
    }

    public override List<Tree>getChild(Tree o)
    {
        List<Tree>list = new List<Tree>();
        list.AddRange(o.child);
        return list;
    }
}

// An example of a tree-structured system to be integrated.
public class Tree
{
    public Tree      sup;
    public String    nme;
    public object    obj { get; set; }
    public List<Tree>child = new List<Tree>();
 
    public Tree(String nme)
    {
        this.nme = nme;
    }
 
    public Tree parent()
    {
        return sup;
    }

    public Tree add(Tree t)
    {
        t.sup = this; child.Add(t); return t;
    }
 
    public Tree find(String n)
    {
        if (nme.Equals(n)) return this;
        for (int i = 0; child != null && i < child.Count; i++) { Tree t = child[i].find(n); if (t != null) return t; }
        return null;
    }
}