I have developed an web app with mern stack. the web app is integrated to an android application with webview react.Is there any way to add upi payments in the application.(phonepay,googlepay)?
You can use the Razorpay payment gateway which provides all different kinds of payment methods like UPI, EMI, Net Banking, Debit Card, Credit Card, etc. You can refer to this link https://razorpay.com/docs/payment-gateway/quick-integration/ for quick integration of Razorpay in your app.
If you want only UPI payments you can also integrate googlepay with the help of Razorpay. see below links to integrate it.