<uses-permission android:name="android.permission.INTERNET" />

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <!--edit text for entering amount to be paid-->
    <EditText
        android:id="@+id/idEdtAmount"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginTop="15dp"
        android:layout_marginEnd="8dp"
        android:hint="Enter Amount to be paid"
        android:inputType="numberDecimal" />

    <!--edit text for entering the upi id
        to which we have to make payment-->
    <EditText
        android:id="@+id/idEdtUpi"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/idEdtAmount"
        android:layout_marginStart="8dp"
        android:layout_marginTop="15dp"
        android:layout_marginEnd="8dp"
        android:hint="Enter your UPI Id"
        android:inputType="text" />

    <!--edit text for adding the name of the
        user whom we have to make payment-->
    <EditText
        android:id="@+id/idEdtName"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/idEdtUpi"
        android:layout_marginStart="8dp"
        android:layout_marginTop="15dp"
        android:layout_marginEnd="8dp"
        android:hint="Enter your Name"
        android:inputType="text" />

    <!--edit text for adding the description for
        the payment which we are making-->
    <EditText
        android:id="@+id/idEdtDescription"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/idEdtName"
        android:layout_marginStart="8dp"
        android:layout_marginTop="15dp"
        android:layout_marginEnd="8dp"
        android:hint="Enter Payment Description"
        android:inputType="text" />

    <!--button for making a payment-->
    <Button
        android:id="@+id/idBtnMakePayment"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/idEdtDescription"
        android:layout_margin="12dp"
        android:text="Make Payment"
        android:textAllCaps="false" />

    <!--text view for displaying transaction status-->
    <TextView
        android:id="@+id/idTVTransactionDetails"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/idBtnMakePayment"
        android:layout_marginTop="30dp"
        android:text="Transaction Details"
        android:textAlignment="center"
        android:textColor="@color/purple_700"
        android:visibility="gone" />

</RelativeLayout>

import android.os.Bundle;
import android.text.TextUtils;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;

import com.shreyaspatil.EasyUpiPayment.EasyUpiPayment;
import com.shreyaspatil.EasyUpiPayment.listener.PaymentStatusListener;
import com.shreyaspatil.EasyUpiPayment.model.TransactionDetails;

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.Locale;

public class MainActivity extends AppCompatActivity implements PaymentStatusListener {

    // initializing variables for our edit text and button.
    private EditText amountEdt, upiEdt, nameEdt, descEdt;
    private TextView transactionDetailsTV;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // initializing all our variables.
        amountEdt = findViewById(R.id.idEdtAmount);
        upiEdt = findViewById(R.id.idEdtUpi);
        nameEdt = findViewById(R.id.idEdtName);
        descEdt = findViewById(R.id.idEdtDescription);
        Button makePaymentBtn = findViewById(R.id.idBtnMakePayment);
        transactionDetailsTV = findViewById(R.id.idTVTransactionDetails);

        // on below line we are getting date and then we are setting this date as transaction id.
        Date c = Calendar.getInstance().getTime();
        SimpleDateFormat df = new SimpleDateFormat("ddMMyyyyHHmmss", Locale.getDefault());
        String transcId = df.format(c);

        // on below line we are adding click listener for our payment button.
        makePaymentBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // on below line we are getting data from our edit text.
                String amount = amountEdt.getText().toString();
                String upi = upiEdt.getText().toString();
                String name = nameEdt.getText().toString();
                String desc = descEdt.getText().toString();
                // on below line we are validating our text field.
                if (TextUtils.isEmpty(amount) && TextUtils.isEmpty(upi) && TextUtils.isEmpty(name) && TextUtils.isEmpty(desc)) {
                    Toast.makeText(MainActivity.this, "Please enter all the details..", Toast.LENGTH_SHORT).show();
                } else {
                    // if the edit text is not empty then
                    // we are calling method to make payment.
                    makePayment(amount, upi, name, desc, transcId);
                }
            }
        });
    }

    private void makePayment(String amount, String upi, String name, String desc, String transactionId) {
        // on below line we are calling an easy payment method and passing 
        // all parameters to it such as upi id,name, description and others.
        final EasyUpiPayment easyUpiPayment = new EasyUpiPayment.Builder()
                .with(this)
                // on below line we are adding upi id.
                .setPayeeVpa(upi)
                // on below line we are setting name to which we are making oayment.
                .setPayeeName(name)
                // on below line we are passing transaction id.
                .setTransactionId(transactionId)
                // on below line we are passing transaction ref id.
                .setTransactionRefId(transactionId)
                // on below line we are adding description to payment.
                .setDescription(desc)
                // on below line we are passing amount which is being paid.
                .setAmount(amount)
                // on below line we are calling a build method to build this ui.
                .build();
        // on below line we are calling a start 
        // payment method to start a payment.
        easyUpiPayment.startPayment();
        // on below line we are calling a set payment
        // status listener method to call other payment methods.
        easyUpiPayment.setPaymentStatusListener(this);
    }

    @Override
    public void onTransactionCompleted(TransactionDetails transactionDetails) {
        // on below line we are getting details about transaction when completed.
        String transcDetails = transactionDetails.getStatus().toString() + "\n" + "Transaction ID : " + transactionDetails.getTransactionId();
        transactionDetailsTV.setVisibility(View.VISIBLE);
        // on below line we are setting details to our text view.
        transactionDetailsTV.setText(transcDetails);
    }

    @Override
    public void onTransactionSuccess() {
        // this method is called when transaction is successful and we are displaying a toast message.
        Toast.makeText(this, "Transaction successfully completed..", Toast.LENGTH_SHORT).show();
    }

    @Override
    public void onTransactionSubmitted() {
        // this method is called when transaction is done 
        // but it may be successful or failure.
        Log.e("TAG", "TRANSACTION SUBMIT");
    }

    @Override
    public void onTransactionFailed() {
        // this method is called when transaction is failure.
        Toast.makeText(this, "Failed to complete transaction", Toast.LENGTH_SHORT).show();
    }

    @Override
    public void onTransactionCancelled() {
        // this method is called when transaction is cancelled.
        Toast.makeText(this, "Transaction cancelled..", Toast.LENGTH_SHORT).show();
    }

    @Override
    public void onAppNotFound() {
        // this method is called when the users device is not having any app installed for making payment.
        Toast.makeText(this, "No app found for making transaction..", Toast.LENGTH_SHORT).show();
    }
}