qr.dart

import 'package:flutter/material.dart';

// for generation QR Code
import 'package:qr_flutter/qr_flutter.dart';


class QRCodeGenerator extends StatefulWidget{
  @override
  _QRCodeGenerator createState() => new _QRCodeGenerator();
}


class _QRCodeGenerator extends State<QRCodeGenerator>{

//  static const double _topSectionTopPadding = 50.0;
//  static const double _topSectionBottomPadding = 20.0;
//  static const double _topSectionHeight = 50.0;


  String _dataString = '1';  //= "{'amount': '2000', 'account':'1234578968574859', 'bank': 'Jamuna bank ltd'}";
  //String _dataString = "{'amount': '2000', 'account':'1234578968574859', 'bank': 'Jamuna bank ltd', 'connectID': '01737388296', 'type': 'payment', 'hello': 'hello world', 'bkash': 'bkash12354'}";
  String _inputErrorText;

  final TextEditingController _controller = new TextEditingController();

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      backgroundColor: Colors.white,
      appBar: new AppBar(
        title: new Text("QR Code Generator"),
      ),

      body: _contentWidget(),
      resizeToAvoidBottomPadding: true,

    );
  }

  @override
  didUpdateWidget(Widget oldWidget){
    super.didUpdateWidget(oldWidget);
    setState((){});
  }

  _contentWidget(){
    final bodyHeight = MediaQuery.of(context).size.height - MediaQuery.of(context).viewInsets.bottom;
    return new Column(
      mainAxisAlignment: MainAxisAlignment.start,
      children: <Widget>[
        new Container(
          child: new TextFormField(
            validator: (val) => val.length >= 10 ? 'Amount is too big': null,
            autofocus: true,
            controller: _controller,
            keyboardType: TextInputType.number,
            //maxLines: 1,
            decoration: new InputDecoration(
              hintText: 'Enter Amount',
              border: new UnderlineInputBorder(),
              filled: true,
              icon: new Icon(Icons.attach_money),
              labelText: "Enter your amount",
              errorText: _inputErrorText,


            ),



          ),
          padding: const EdgeInsets.all(20.0),
        ),

        new Container(
          child: new RaisedButton(
            onPressed: () {
              setState((){
                _dataString = _controller.text;
                _inputErrorText = null;
              });

//              showDialog(
//                context: context,
//                child: new AlertDialog(
//                  title: new Text('What you typed'),
//                  content: new Text(_controller.text),
//                ),
//              );
            },
            child: new Text("Generate"),
            color: Colors.redAccent,
            textColor: Colors.white,
          ),
        ),
        new Expanded(
          child: new Center(
            child: new QrImage(
                data: _dataString,
                size: 0.5 * bodyHeight,
                version: 15,
                onError: (ex){
                  print("QR Erorr - $ex");
                  setState((){
                    _inputErrorText = "Error ! message ";
                  });
                },
            ),
          ),
        ),
      ],
    );
  }
}