If you want to add circular pie chart in your application then RingPieChart can be a good choice containing number of animations and its Easy to use framework

自定义View之扇形饼状图

In this application, you can track the covid data such as total cases, deaths, active, etc of all the countries and as well as all states of India. You can also check the vaccine slot availability data.

This is simple application used to how to render Pie Chart using Canvas and Paint. It would render the chart by given data

Finance Manager is a Java-based desktop application designed to help users manage their personal finances. It allows users to record inflows (income) and outflows (expenses), automatically generate financial statements, and store them as PDF files. The app also features pie charts and bar graphs to visually display users' financial data.

A simple MERN based voting App.This app provides Piechart view for voting results

An android app that provides statistics of a codeforces user using the codeforces api

Android App that facilitates buying and selling of goods