How to Implement a Loading Page for All Routes in Flask?

I'm developing a Flask web application and I want to implement a loading page that appears while the content of each page is being loaded. This loading page should be displayed for all routes, including error pages like 404 errors.

I've created a loading page template (loading.html) with a simple loading animation, and I'm using Flask's routing system to define the routes. However, I'm not sure how to integrate the loading page into my application to ensure it appears before each page is loaded.

Here's what I've tried so far:

from flask import render_template@app.route('/')def index():    return render_template('loading.html')    # Perform necessary actions    # Render main HTML page@app.errorhandler(404)def not_found_error(error):    return render_template('loading.html')    # Perform necessary actions    # Render 404 error page

However, this approach doesn't seem to be working as expected. The loading page is displayed, but the main HTML page isn't rendered afterward.

Can someone provide guidance on how to properly implement a loading page that appears before each page is loaded in Flask? Any help or suggestions would be greatly appreciated.