当我按下“查看更多”按钮时，什么也没有发生，我该怎么办

Question

当我按下“查看更多”按钮时，什么也没有发生，我该怎么办，它应该在浏览器应用程序的url列表中启动一个网站，但是那没有发生，

import 'package:flutter/material.dart';
import 'package:wwdc/data.dart';
import 'dart:math';
import 'package:url_launcher/url_launcher.dart';

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => new _MyAppState();
}

var cardAspectRatio = 12.0 / 16.0;
var widgetAspectRatio = cardAspectRatio * 1.2;

class _MyAppState extends State<MyApp> {
  var currentPage = images.length - 1.0;

  @override
  Widget build(BuildContext context) {
    PageController controller = PageController(initialPage: images.length - 1);
    controller.addListener(() {
      setState(() {
        currentPage = controller.page;
      });
    });

    return Container(
      decoration: BoxDecoration(
          gradient: LinearGradient(
              colors: [
            Color(0xFF1b1e44),
            Color(0xFF2d3447),
          ],
              begin: Alignment.bottomCenter,
              end: Alignment.topCenter,
              tileMode: TileMode.clamp)),
      child: Scaffold(
        backgroundColor: Colors.black45,
        body: SingleChildScrollView(
          child: Column(
            children: <Widget>[
              SizedBox(
                height: 100,
              ),
              Padding(
                padding: EdgeInsets.symmetric(horizontal: 20.0),
                child: Row(
                  mainAxisAlignment: MainAxisAlignment.spaceBetween,
                  children: <Widget>[
                    Text("Releases",
                        style: TextStyle(
                          color: Colors.white,
                          fontSize: 46.0,
                          fontFamily: "Calibre-Semibold",
                          letterSpacing: 1.0,
                        )),
                  ],
                ),
              ),
              Stack(
                children: <Widget>[
                  CardScrollWidget(currentPage),
                  Positioned.fill(
                    child: PageView.builder(
                      itemCount: images.length,
                      controller: controller,
                      reverse: true,
                      itemBuilder: (context, index) {
                        return Container();
                      },
                    ),
                  )
                ],
              ),
            ],
          ),
        ),
      ),
    );
  }
}

class CardScrollWidget extends StatelessWidget {
  List<String> urls = [
    'https://www.apple.com/watchos/watchos-preview/',
    'https://www.apple.com/macos/big-sur-preview/',
    'https://www.apple.com/ipados/ipados-preview/',
    'https://www.apple.com/ios/ios-14-preview/'
  ];

  var currentPage;
  var padding = 20.0;
  var verticalInset = 20.0;

  //var k=0;
  CardScrollWidget(this.currentPage);

  @override
  Widget build(BuildContext context) {
    return new AspectRatio(
      aspectRatio: widgetAspectRatio,
      child: LayoutBuilder(builder: (context, contraints) {
        var width = contraints.maxWidth;
        var height = contraints.maxHeight;

        var safeWidth = width - 2 * padding;
        var safeHeight = height - 2 * padding;

        var heightOfPrimaryCard = safeHeight;
        var widthOfPrimaryCard = heightOfPrimaryCard * cardAspectRatio;

        var primaryCardLeft = safeWidth - widthOfPrimaryCard;
        var horizontalInset = primaryCardLeft / 2;

        List<Widget> cardList = new List();

        for (var i = 0; i < images.length; i++) {
          var delta = i - currentPage;
          bool isOnRight = delta > 0;
          print(i);
          var start = padding +
              max(
                  primaryCardLeft -
                      horizontalInset * -delta * (isOnRight ? 15 : 1),
                  0.0);

          var cardItem = Positioned.directional(
            top: padding + verticalInset * max(-delta, 0.0),
            bottom: padding + verticalInset * max(-delta, 0.0),
            start: start,
            textDirection: TextDirection.rtl,
            child: ClipRRect(
              borderRadius: BorderRadius.circular(16.0),
              child: Container(
                decoration: BoxDecoration(color: Colors.white, boxShadow: [
                  BoxShadow(
                      color: Colors.black12,
                      offset: Offset(3.0, 6.0),
                      blurRadius: 10.0)
                ]),
                child: AspectRatio(
                  aspectRatio: cardAspectRatio,
                  child: Stack(
                    fit: StackFit.expand,
                    children: <Widget>[
                      Image.asset(images[i], fit: BoxFit.cover),
                      Align(
                        alignment: Alignment.bottomLeft,
                        child: Column(
                          mainAxisSize: MainAxisSize.min,
                          crossAxisAlignment: CrossAxisAlignment.start,
                          children: <Widget>[
                            Padding(
                              padding: const EdgeInsets.all(5.0),
                              child: Container(
                                decoration: BoxDecoration(
                                  borderRadius:
                                      BorderRadius.all(Radius.circular(30)),
                                  color: Color.fromRGBO(0, 0, 0, 0.3),
                                ),
                                padding: EdgeInsets.symmetric(
                                    horizontal: 16.0, vertical: 8.0),
                                child: Text(title[i],
                                    style: TextStyle(
                                      color: Colors.white,
                                      fontSize: 35.0,
                                    )),
                              ),
                            ),
                            SizedBox(
                              height: 10.0,
                            ),
                            Padding(
                                padding: const EdgeInsets.all(5),
                                child: ButtonTheme(
                                    // buttonColor: Colors.white,
                                    child: RaisedButton(
                                  color: Colors.white,
                                  shape: RoundedRectangleBorder(
                                    borderRadius: BorderRadius.circular(30.0),
                                  ),
                                  child: new Text(
                                    "View More",
                                    style: TextStyle(
                                      color: Colors.black45,
                                      fontSize: 25,
                                    ),
                                  ),
                                  onPressed: () async {
                                    String url = urls[i];
                                    if (await canLaunch(url)) {
                                      await launch(url);
                                    } else {
                                      throw 'Could not launch $url';
                                    }
                                    //i++;
                                    print("inside");
                                  },
                                )))
                          ],
                        ),
                      )
                    ],
                  ),
                ),
              ),
            ),
          );
          cardList.add(cardItem);
        }
        return Stack(
          children: cardList,
        );
      }),
    );
  }
}