anchor.diff:    @override
     Widget build(BuildContext context) {
       return Scaffold(
  -      appBar: AppBar(
  -        title: const Text('Google Pay T-shirt Shop'),
  -      ),
  -      backgroundColor: Colors.white,
  -      body: ListView(
  -        padding: EdgeInsets.symmetric(horizontal: 20),
  -        children: [
  +        appBar: AppBar(
  +          title: const Text('Google Pay T-shirt Shop'),
  +        ),
  +        backgroundColor: Colors.white,
  +        body:
  +            ListView(padding: EdgeInsets.symmetric(horizontal: 20), children: [
             Container(
  -            margin: const EdgeInsets.symmetric(vertical: 20),
  -            child: Image(
  -                image: AssetImage('assets/images/ts_10_11019a.jpg'),
  -                height: 350
  -            )
  -          ),
  -          Text('Amanda\'s Polo Shirt',
  +              margin: const EdgeInsets.symmetric(vertical: 20),
  +              child: Image(
  +                  image: AssetImage('assets/images/ts_10_11019a.jpg'),
  +                  height: 350)),
  +          Text(
  +            'Amanda\'s Polo Shirt',
               style: TextStyle(
  -              fontSize: 20,
  +                fontSize: 20,
                   color: Color(0xff333333),
  -                fontWeight:FontWeight.bold
  -            ),
  +                fontWeight: FontWeight.bold),
             ),
             SizedBox(height: 5),
  -          Text('\$50.20',
  +          Text(
  +            '\$50.20',
               style: TextStyle(color: Color(0xff777777), fontSize: 15),
             ),
             SizedBox(height: 15),
  -          Text('Description',
  +          Text(
  +            'Description',
               style: TextStyle(
                   fontSize: 15,
                   color: Color(0xff333333),
  -                fontWeight:FontWeight.bold
  -            ),
  +                fontWeight: FontWeight.bold),
             ),
             SizedBox(height: 5),
             Text(
  -            'A versatile full-zip that you can wear all day long and even...',
  -            style: TextStyle(color: Color(0xff777777), fontSize: 15)
  -          ),
  +              'A versatile full-zip that you can wear all day long and even...',
  +              style: TextStyle(color: Color(0xff777777), fontSize: 15)),
             SizedBox(height: 15),
             Center(child: _getPaymentButtons())
  -        ]
  -      )
  -    );
  +        ]));
     }
   }
  
positive.code:           if (snapshot.data == true) {
              return SizedBox(
                  width: double.infinity,
                  child: GooglePayButton(onPressed: googlePayButtonPressed)
              );
  
            } else if (snapshot.hasError) {
              PlatformException exc = snapshot.error;
              return Text(exc.message);
  
negative.code: }
  
  class _GooglePaySampleAppState extends State<GooglePaySampleApp> {
    void googlePayButtonPressed() async {
      var result = await _googlePayClient.showPaymentSelector();
      debugPrint(result.toString());
    }
  
    Widget _getPaymentButtons() {
  