Multilevel Tree Dropdown Callback Functions

tldr; I have been trying to use a custom dash component, and cannot get the callback function to trigger when a checkbox is clicked in the custom component. The callback gets triggered once at the start and then never again. Any thoughts on possible causes would be greatly appreciated!


I have been trying to use this dash component for a webapp:

I want a callback function to trigger any time a checkbox is selected or unselected. I wrote some code to test the input to the callback function, but it does not work. The callback function seems to trigger once on startup, and never again.

I have posted an issue here: Clicking items does not trigger callback function, cannot retrieve selected items in python · Issue #28 · westonkjones/dash-dropdown-tree-select · GitHub

This is the code I ran, with shortened data.

#!/usr/bin/env python
# coding: utf-8

# In[1]:


import dash_dropdown_tree_select
import dash
from dash.dependencies import Input, Output
from dash import html


# In[2]:


app = dash.Dash(__name__)


# In[3]:


data = [
  {
    "label": "VP Accounting",
    "tagClassName": "special",
    "children": [
      {
        "label": "iWay",
        "children": [
          {
            "label": "Universidad de Especialidades del EspĂ­ritu Santo"
          },
          {
            "label": "Marmara University"
          },
          {
            "label": "Baghdad College of Pharmacy"
          }
        ]
      },
      {
        "label": "KDB",
        "children": [
          {
            "label": "Latvian University of Agriculture"
          },
          {
            "label": "Dublin Institute of Technology"
          }
        ]
      },
      {
        "label": "Justice",
        "children": [
          {
            "label": "Baylor University"
          },
          {
            "label": "Massachusetts College of Art"
          },
          {
            "label": "Universidad TĂ©cnica Latinoamericana"
          },
          {
            "label": "Saint Louis College"
          },
          {
            "label": "Scott Christian University"
          }
        ]
      },
      {
        "label": "Utilization Review",
        "children": [
          {
            "label": "University of Minnesota - Twin Cities Campus"
          },
          {
            "label": "Moldova State Agricultural University"
          },
          {
            "label": "Andrews University"
          },
          {
            "label": "Usmanu Danfodiyo University Sokoto"
          }
        ]
      },
      {
        "label": "Norton Utilities",
        "children": [
          {
            "label": "Universidad AutĂłnoma del Caribe"
          },
          {
            "label": "National University of Uzbekistan"
          },
          {
            "label": "Ladoke Akintola University of Technology"
          },
          {
            "label": "Kohat University of Science and Technology  (KUST)"
          },
          {
            "label": "Hvanneyri Agricultural University"
          }
        ]
      }
    ]
  },
  {
    "label": "Database Administrator III",
    "children": [
      {
        "label": "TFS",
        "children": [
          {
            "label": "University of Jazeera"
          },
          {
            "label": "Technical University of Crete"
          },
          {
            "label":
              "Ecole Nationale Supérieure d'Agronomie et des Industries Alimentaires"
          },
          {
            "label": "Ho Chi Minh City University of Natural Sciences"
          }
        ]
      },
      {
        "label": "Overhaul",
        "children": [
          {
            "label": "Technological University (Taunggyi)"
          },
          {
            "label": "Universidad de Las Palmas de Gran Canaria"
          },
          {
            "label": "Olympia College"
          },
          {
            "label": "Franklin and Marshall College"
          },
          {
            "label":
              "State University of New York College of Environmental Science and Forestry"
          }
        ]
      },
      {
        "label": "GTK",
        "children": [
          {
            "label": "Salisbury State University"
          },
          {
            "label":
              "Evangelische Fachhochschule für Religionspädagogik, und Gemeindediakonie Moritzburg"
          },
          {
            "label": "Kilimanjaro Christian Medical College"
          }
        ]
      },
      {
        "label": "SRP",
        "children": [
          {
            "label": "Toyo Gakuen University"
          },
          {
            "label": "Riyadh College of Dentistry and Pharmacy"
          },
          {
            "label": "Aichi Gakusen University"
          }
        ]
      }
    ]
  },
  {
    "label": "Assistant Manager",
    "children": [
      {
        "label": "Risk Analysis",
        "children": [
          {
            "label": "Seijo University"
          },
          {
            "label": "University of Economics Varna"
          },
          {
            "label": "College of Technology at Riyadh"
          }
        ]
      },
      {
        "label": "UV Mapping",
        "children": [
          {
            "label": "Universidad de La Sabana"
          },
          {
            "label": "Pamukkale University"
          }
        ]
      }
    ]
  }
]


# In[4]:


app.layout = html.Div([
    dash_dropdown_tree_select.DashDropdownTreeSelect(
        id = "dropdown",
        data=data,
    ),
    html.H1(id = "txt", children = "0")
])


# In[5]:


@app.callback(
    Output('txt', 'children'),
    [Input('dropdown', 'onChange'),
     Input('txt','children')
    ]
)
def updated_checkbox(sel, count):
    counter = int(count)
    counter +=1
    ret = str(counter)
    return ret


# In[ ]:


if __name__ == '__main__':
    app.run_server(debug=False)


Instead of onChange, I have also tried onNodeToggle and onAction as inputs to the callback function. The expected behavior of this code is to increment the counter every time a node is checked or unchecked. The end goal is to obtain a list of all checked nodes every time a node is checked or unchecked.