UpiPayment.dart

UpiPayment.dart

import 'dart:math';
import 'package:flutter/material.dart';
import 'package:upi_pay/upi_pay.dart';

class UpiPayment extends StatefulWidget {
  @override
  _UpiPaymentState createState() => _UpiPaymentState();
}

class _UpiPaymentState extends State<UpiPayment> {

  // used for storing errors.
  String _upiAddrError;

  // used for defining amount and UPI address of merchant where
  // payment is to be received.
  TextEditingController _upiAddressController = TextEditingController();
  TextEditingController _amountController = TextEditingController();

  // used for showing list of UPI apps installed in current device
  Future<List<ApplicationMeta>> _appsFuture;

  @override
  void initState() {
    super.initState();

   // we have declared amount as 999 (i.e. Rs.999).
    _amountController.text = (999).toString();

    // we have used sample UPI address (will be used to receive amount)
    _upiAddressController.text = 'ry4761@okhdfcbank';
    
  // used for getting list of UPI apps installed in current device
    _appsFuture = UpiPay.getInstalledUpiApplications();
  }

  @override
  void dispose() {

    // dispose text field controllers after use.
    _upiAddressController.dispose();
    _amountController.dispose();
    super.dispose();
  }

  // this will open correspondence UPI Payment gateway app on which user has tapped.
  Future<void> _openUPIGateway(ApplicationMeta app) async {
    final err = _validateUpiAddress(_upiAddressController.text);
    if (err != null) {
      setState(() {
        _upiAddrError = err;
      });
      return;
    }
    setState(() {
      _upiAddrError = null;
    });

    final transactionRef = Random.secure().nextInt(1 << 32).toString();
    print("Starting transaction with id $transactionRef");

    // this function will initiate UPI transaction.
    final a = await UpiPay.initiateTransaction(
      amount: _amountController.text,
      app: app.upiApplication,
      receiverName: 'Sharad',
      receiverUpiAddress: _upiAddressController.text,
      transactionRef: transactionRef,
      merchantCode: '7372',
    );

    print(a);
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: true,
      home: Scaffold(
        appBar: AppBar(title: Text('UPI Payment')),
        body: SafeArea(
          child: Container(
            padding: EdgeInsets.symmetric(horizontal: 16),
            child: ListView(
              children: <Widget>[
                Container(
                  margin: EdgeInsets.only(top: 32),
                  child: Row(
                    children: <Widget>[
                      Expanded(
                        child: TextFormField(
                          controller: _upiAddressController,
                          enabled: false,
                          decoration: InputDecoration(
                            border: OutlineInputBorder(),
                            hintText: 'address@upi',
                            labelText: 'Receiving UPI Address',
                          ),
                        ),
                      ),
                    ],
                  ),
                ),
                if (_upiAddrError != null)
                  Container(
                    margin: EdgeInsets.only(top: 4, left: 12),
                    child: Text(
                      _upiAddrError,
                      style: TextStyle(color: Colors.red),
                    ),
                  ),
                Container(
                  margin: EdgeInsets.only(top: 32),
                  child: Row(
                    children: <Widget>[
                      Expanded(
                        child: TextField(
                          controller: _amountController,
                          readOnly: true,
                          enabled: false,
                          decoration: InputDecoration(
                            border: OutlineInputBorder(),
                            labelText: 'Amount',
                          ),
                        ),
                      ),
                    ],
                  ),
                ),
                Container(
                  margin: EdgeInsets.only(top: 128, bottom: 32),
                  child: Column(
                    mainAxisSize: MainAxisSize.min,
                    children: <Widget>[
                      Container(
                        margin: EdgeInsets.only(bottom: 12),
                        child: Text(
                          'Pay Using',
                          style: Theme.of(context).textTheme.caption,
                        ),
                      ),
                      FutureBuilder<List<ApplicationMeta>>(
                        future: _appsFuture,
                        builder: (context, snapshot) {
                          if (snapshot.connectionState != ConnectionState.done) {
                            return Container();
                          }

                          return GridView.count(
                            crossAxisCount: 2,
                            shrinkWrap: true,
                            mainAxisSpacing: 8,
                            crossAxisSpacing: 8,
                            childAspectRatio: 1.6,
                            physics: NeverScrollableScrollPhysics(),
                            children: snapshot.data.map((i) => Material(
                              key: ObjectKey(i.upiApplication),
                              color: Colors.grey[200],
                              child: InkWell(
                                onTap: () => _openUPIGateway(i),
                                child: Column(
                                  mainAxisSize: MainAxisSize.min,
                                  mainAxisAlignment: MainAxisAlignment.center,
                                  children: <Widget>[
                                    Image.memory(
                                      i.icon,
                                      width: 64,
                                      height: 64,
                                    ),
                                    Container(
                                      margin: EdgeInsets.only(top: 4),
                                      child: Text(
                                        i.upiApplication.getAppName(),
                                      ),
                                    ),
                                  ],
                                ),
                              ),
                            ))
                                .toList(),
                          );
                        },
                      ),
                    ],
                  ),
                )
              ],
            ),
          )
        ),
      )
    );
  }
}

String _validateUpiAddress(String value) {
  if (value.isEmpty) {
    return 'UPI Address is required.';
  }

  if (!UpiPay.checkIfUpiAddressIsValid(value)) {
    return 'UPI Address is invalid.';
  }

  return null;
}