使用 Flutter/Dart 的 URL 启动器

Posted 2023-03-07

【中文标题】使用 Flutter/Dart 的 URL 启动器

【英文标题】：Url Launcher using Flutter/Dart

【发布时间】：2020-08-02 01:05:00

【问题描述】：

大家晚上好，

我在使用 URL 启动器时遇到了一点问题。基本上，我要做的是从 Future 函数（从 API 检索）获取 URL，然后在按下凸起按钮后导航到该 URL。我实现的代码有效，但并非没有一个小而讨厌的错误。错误出现大约半秒到一秒（我假设直到 API 返回 URL），然后凸起的按钮被绘制到屏幕上并且工作正常；然后我可以导航到该站点。我试图完全摆脱这个错误。为了节省您一些时间，相关的 FutureBuilder 是第二个。以下是我的代码：

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:url_launcher/url_launcher.dart';

import '../models/yahoo_finance_stock_info.dart';
import '../providers/companies_provider.dart';

class BusinessScreen extends StatefulWidget 
  static const routeName = '/business-screen';

  @override
  _BusinessScreenState createState() => _BusinessScreenState();


class _BusinessScreenState extends State<BusinessScreen>
    with AutomaticKeepAliveClientMixin<BusinessScreen> 
  @override
  bool get wantKeepAlive => true;

  Future _companyDescription;
  Future _urlForUrlLauncher;

  var _isInit = true;

  @override
  void didChangeDependencies() 
    if (_isInit) 
      final companyTicker = ModalRoute.of(context).settings.arguments as String;
      final loadedCompany = Provider.of<Companies>(context, listen: false)
          .findByTicker(companyTicker);

      _companyDescription =
          Companies().getSecurityExtendStats(loadedCompany.tickerSymbol);

      _urlForUrlLauncher =
          Companies().getHistoricalData(loadedCompany.tickerSymbol);
    
    _isInit = false;
    super.didChangeDependencies();
  

  @override
  void initState() 
    // TODO: implement initState
    super.initState();
    _companyDescription;
  

  @override
  Widget build(BuildContext context) 
    super.build(context);
    final companyTicker = ModalRoute.of(context).settings.arguments as String;
    final loadedCompany = Provider.of<Companies>(context, listen: false)
        .findByTicker(companyTicker);

    return Container(
      color: Colors.black87,
      child: Column(
        children: <Widget>[
          Container(
            height: 300,
            width: double.infinity,
            color: Colors.white,
            padding: EdgeInsets.all(10),
            child: SingleChildScrollView(
              padding: EdgeInsets.only(left: 15),
              scrollDirection: Axis.vertical,
              child: FutureBuilder<StockInformation>(
                future: _companyDescription,
                builder: (BuildContext context,
                    AsyncSnapshot<StockInformation> snapshot) 
                  if (snapshot.data != null) 
                    return Text(snapshot.data.assetProfile.longBusinessSummary);
                  
                  return Container(
                    height: 300,
                    child: Center(
                      child: CircularProgressIndicator(),
                    ),
                  );
                ,
              ),
            ),
          ),
          Container(
            height: 75,
            width: double.infinity,
            child: Center(
              child: FutureBuilder(
                future: _urlForUrlLauncher,
                builder: (BuildContext context, AsyncSnapshot snapshot) 
                  if (snapshot.data[0]['finalLink'] != null) 
                    String url10K = snapshot.data[0]['finalLink'];
                    return RaisedButton(
                      shape: RoundedRectangleBorder(
                        borderRadius: BorderRadius.circular(10),
                        side: BorderSide(
                          color: Colors.grey,
                          width: 1,
                        ),
                      ),
                      onPressed: () async 
                        var url = url10K;
                        if (await canLaunch(url)) 
                          await launch(url);
                         else 
                          throw 'Could not launch $url';
                        
                      ,
                      child: Text(
                        'Go to company\'s filings',
                        style: TextStyle(
                          color: Colors.white,
                        ),
                      ),
                    );
                   else 
                    return RaisedButton(
                      shape: RoundedRectangleBorder(
                        borderRadius: BorderRadius.circular(10),
                        side: BorderSide(
                          color: Colors.grey,
                          width: 1,
                        ),
                      ),
                      onPressed: null,
                      child: Text(
                        'Go to company\'s filings',
                        style: TextStyle(color: Colors.white,),
                      ),
                    );
                  
                ,
              ),
            ),
          )
        ],
      ),
    );
  

在此先感谢您对此问题的所有帮助！

【参考方案1】：

在第二个FutureBuilder改变条件，

builder: (BuildContext context, AsyncSnapshot snapshot) 
  if (snapshot.data != null && snapshot.data[0]['finalLink'] != null) 
    // raised button with onpressed
   else 
    // raised button with onpressed as null