从多个网站抓取数据的最佳方法是什么？

Question

我尝试过的是，我使用 volley request 从第一个网站抓取，并在其中为每个网站创建了多个线程，并且在每个线程内我使用 jsoup connect 方法来抓取而不是 volley。它可以完成工作，实际上更快。但是，问题是它在抓取数据时冻结了应用程序，直到它完全加载。它冻结了进度条，我无法找到原因。

这是我实现的代码。有点长。

//        Checking the connection
        final StringRequest request = new StringRequest("https://www.google.com/", new Response.Listener<String>() {
            @Override
            public void onResponse(String response) {


                relativeLayout.setVisibility(View.GONE);


//                instances for each required website
                final HimalayanTimes himalayanTimes = new HimalayanTimes(getContext());
                final GsmArena gsmArena = new GsmArena();
                final CinemaBlend cinemaBlend = new CinemaBlend();
                final KathmanduPost kathmanduPost = new KathmanduPost(getContext());
                final GlobalNews globalNews =  new GlobalNews();
                final NepaliTimes nepaliTimes = new NepaliTimes(getContext());
                final GoalNepal goalNepal = new GoalNepal(getContext());
                final GadgetByte gadgetByte = new GadgetByte();
                final TechLekh techLekh = new TechLekh();
                final OnlineKhabar onlineKhabar = new OnlineKhabar();
                final NepaliSansar nepaliSansar = new NepaliSansar();
                final CricketingNepal cricketingNepal = new CricketingNepal();




//                thread for each website
//                thread fot thehimalayantimes


                Thread thread = new Thread(new Runnable() {
                    @Override
                    public void run() {
                        try  {
                            ArrayList<NewsItem> himalyannews;
                            himalyannews = himalayanTimes.getNews();
                            news.addAll(himalyannews);
                            for(int i=0; i<4; i++){
                                finalHeadlines.add(himalyannews.get(i));
                            }
                        } catch (Exception ignored) {
                        }
                    }
                });
                thread.start();



//                thread for gsmArena
                Thread thread1 = new Thread(new Runnable() {
                    @Override
                    public void run() {
                        try  {
                            ArrayList<NewsItem> gsmarenanews;
                            gsmarenanews = gsmArena.getNews();
                            news.addAll(gsmarenanews);
                            for(int i=0; i<3; i++){
                                headlines.add(gsmarenanews.get(i));
                            }
                        } catch (Exception ignored) {
                        }
                    }
                });
                thread1.start();




//                thread for cinemaBlend
                Thread thread2 = new Thread(new Runnable() {
                    @Override
                    public void run() {
                        try  {
                            ArrayList<NewsItem> cinemablendnews;
                            cinemablendnews = cinemaBlend.getNews();
                            news.addAll(cinemablendnews);
                            for(int i=0; i<4; i++){
                                headlines.add(cinemablendnews.get(i));
                            }
                        } catch (Exception ignored) {
                        }
                    }
                });
                thread2.start();





//                thread for kathmanduPost
                Thread thread3 = new Thread(new Runnable() {
                    @Override
                    public void run() {
                        try {
                            ArrayList<NewsItem> kathmandupostnews;
                            kathmandupostnews = kathmanduPost.getNews();
                            news.addAll(kathmandupostnews);
                            for(int i=0; i<3; i++){
                                finalHeadlines.add(kathmandupostnews.get(i));
                            }
                        } catch (IOException ignored) {
                        }
                    }
                });
                thread3.start();



//                thread for globalNews
                Thread thread4 = new Thread(new Runnable() {
                    @Override
                    public void run() {
                        try {
                            ArrayList<NewsItem> globalnewsnews;
                            globalnewsnews = globalNews.getNews();
                            news.addAll(globalnewsnews);
                            for(int i=0; i<5; i++){
                                finalHeadlines.add(globalnewsnews.get(i));
                            }
                        } catch (IOException ignored) {
                        }
                    }
                });
                thread4.start();



//                thread for nepaliTimes
                Thread thread5 = new Thread(new Runnable() {
                    @Override
                    public void run() {
                        try {
                            ArrayList<NewsItem> nepalitimesnews;
                            nepalitimesnews = nepaliTimes.getNews();
                            news.addAll(nepalitimesnews);
                            for(int i=0; i<3; i++){
                                finalHeadlines.add(nepalitimesnews.get(i));
                            }
                        } catch (IOException ignored) {
                        }
                    }
                });
                thread5.start();


//                thread for GoalNepal
                Thread thread6 = new Thread(new Runnable() {
                    @Override
                    public void run() {
                        try {
                            ArrayList<NewsItem> goalNepalNews;
                            goalNepalNews = goalNepal.getNews();
                            news.addAll(goalNepalNews);
                            for (int i=0; i<4; i++){
                                headlines.add(goalNepalNews.get(i));
                            }
                        } catch (IOException ignored) {
                        }
                    }
                });
                thread6.start();



//                thread for GadgetByteNepal
                Thread thread7 = new Thread(new Runnable() {
                    @Override
                    public void run() {
                        try {
                            ArrayList<NewsItem> gadgetbytenews;
                            gadgetbytenews = gadgetByte.getNews();
                            news.addAll(gadgetbytenews);
                            for (int i=0; i<3; i++){
                                headlines.add(gadgetbytenews.get(i));
                            }
                        } catch (IOException ignored) {
                        }
                    }
                });
                thread7.start();




//                thread for Techlekh
                Thread thread8 = new Thread(new Runnable() {
                    @Override
                    public void run() {
                        try {
                            ArrayList<NewsItem> techlekhnews;
                            techlekhnews = techLekh.getNews();
                            news.addAll(techlekhnews);
                            for (int i=0; i<3; i++){
                                headlines.add(techlekhnews.get(i));
                            }
                        } catch (IOException ignored) {
                        }
                    }
                });
                thread8.start();



                //                thread for onlinekhabar
                Thread thread9 = new Thread(new Runnable() {
                    @Override
                    public void run() {
                        try {
                            ArrayList<NewsItem> onlineKhabarnews;
                            onlineKhabarnews = onlineKhabar.getNews();
                            news.addAll(onlineKhabarnews);
                            for (int i=0; i<4; i++){
                                finalHeadlines.add(onlineKhabarnews.get(i));
                            }
                        } catch (IOException ignored) {
                        }
                    }
                });
                thread9.start();



                //thread for nepalisansar
                Thread thread11 = new Thread(new Runnable() {
                    @Override
                    public void run() {
                        try {
                            ArrayList<NewsItem> nepalisansarnews;
                            nepalisansarnews = nepaliSansar.getNews();
                            news.addAll(nepalisansarnews);
                            for (int i=0; i<4; i++){
                                finalHeadlines.add(nepalisansarnews.get(i));
                            }
                        } catch (IOException ignored) {
                        }
                    }
                });
                thread11.start();



//                thread for cricketingNepal
                Thread thread12 = new Thread(new Runnable() {
                    @Override
                    public void run() {
                        try {
                            ArrayList<NewsItem> cricketnews;
                            cricketnews = cricketingNepal.getNews();
                            news.addAll(cricketnews);
                            for (int i=0; i<4; i++){
                                headlines.add(cricketnews.get(i));
                            }
                        } catch (IOException ignored) {
                        }
                    }
                });
                thread12.start();





//                main thread wait for each thread to finish

                try {
                    thread.join();
                } catch (InterruptedException ignored) {
                }


                try {
                    thread1.join();
                } catch (InterruptedException ignored) {

                }




                try {
                    thread2.join();
                } catch (InterruptedException ignored) {

                }



                try {
                    thread3.join();
                } catch (InterruptedException ignored) {
                }




                try {
                    thread4.join();
                } catch (InterruptedException ignored) {
                }



                try {
                    thread5.join();
                } catch (InterruptedException ignored) {
                }



                try {
                    thread6.join();
                } catch (InterruptedException ignored) {
                }



                try {
                    thread7.join();
                } catch (InterruptedException ignored) {
                }


                try {
                    thread8.join();
                } catch (InterruptedException ignored) {
                }



                try {
                    thread8.join();
                } catch (InterruptedException ignored) {
                }


                try {
                    thread9.join();
                } catch (InterruptedException ignored) {
                }



                try {
                    thread11.join();
                } catch (InterruptedException ignored) {
                }

                try {
                    thread12.join();
                } catch (InterruptedException ignored) {
                }



                for(NewsItem item : news){
                    if (item.tag.contains("kathmandu"))
                        nepal.add(item);
                    if (item.tag.contains("cricket"))
                        sports.add(item);
                    if (item.tag.contains("football"))
                        sports.add(item);
                    switch (item.tag) {
                        case "nepal":
                            nepal.add(item);
                            break;
                        case "world":
                            world.add(item);
                            break;
                        case "sports":
                            sports.add(item);
                            break;
                        case "tech":
                            tech.add(item);
                            break;
                        case "entertainment":
                            entertainment.add(item);
                            break;
                    }
                }


                //                putting each news item to the main container
                Collections.shuffle(headlines);

                Collections.shuffle(finalHeadlines);
                finalHeadlines.addAll(headlines);
                Collections.shuffle(nepal);
                Collections.shuffle(world);
                Collections.shuffle(sports);
                Collections.shuffle(tech);
                Collections.shuffle(entertainment);




                tab1 t1 = new tab1(finalHeadlines);
                t1.setRetainInstance(true);

                tab2 t2 = new tab2(nepal);
                t2.setRetainInstance(true);

                tab3 t3 = new tab3(world);
                t3.setRetainInstance(true);

                tab4 t4 = new tab4(sports);
                t4.setRetainInstance(true);

                tab5 t5 = new tab5(tech);
                t5.setRetainInstance(true);

                tab6 t6 = new tab6(entertainment);
                t6.setRetainInstance(true);

                assert getFragmentManager() != null;
                pagerAdapter = new PageAdapter(finalHeadlines, nepal, world, sports, tech, entertainment, getFragmentManager(), tabLayout.getTabCount());
                viewPager.setAdapter(pagerAdapter);
                shimmerFrameLayout.setVisibility(View.GONE);


            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                Toast.makeText(getContext(), "Internet Connection Error!", Toast.LENGTH_SHORT).show();
                shimmerFrameLayout.setVisibility(View.GONE);
                tabLayout.setVisibility(View.GONE);
            }
        });
        queue.add(request);

对于每个网站，我都做了课程。以下类之一：-

public class CinemaBlend {
    ArrayList<NewsItem> news;

    public CinemaBlend() {
        news = new ArrayList<>();
    }

    @RequiresApi(api = Build.VERSION_CODES.KITKAT)
    public ArrayList<NewsItem> getNews() throws IOException{

        String url = "https://www.cinemablend.com/news.php";
        OkHttpClient okHttpClient = new OkHttpClient();
        Request request = new Request.Builder().url(url).get().build();
        Document document = Jsoup.parse(Objects.requireNonNull(okHttpClient.newCall(request).execute().body()).string());
        Elements articles = document.select("div.order-of-type-2").select("div.story-related").select("a");

        for(Element article : articles)
        {
            String link = article.attr("href");
            String title = article.attr("title");
            String img = article.select("div.story-related-content").select("span.story-cover-image").select("img").attr("data-src");
            String date = article.select("span.story-related-published-date").text();

            NewsItem newsItem = new NewsItem();
            newsItem.imgsrc = img;
            newsItem.title = title;
            newsItem.link = link;
            newsItem.tag = "entertainment";
            newsItem.publisher = "cinemablend.com";
            newsItem.source_logo = "https://image.pitchbook.com/WFQVGYL17V0MevlcfQKlWjC3E8K1447542818374_200x200";

            if(!date.equals(""))
            {
                newsItem.date = date + " ago";
                news.add(newsItem);
            }
        }

        return news;
    }
}

Answer 1

寻找解释如何执行后台工作的教程。有很多不同的方法可以做到这一点：服务、Kotlin 协程、简单的自我管理线程等。

远离关于 AsyncTasks 和 Loaders 的教程（已弃用）。

Android 开发者指南是一个很好的起点：https://developer.android.com/guide/background

Answer 2

但是在异步任务中执行任务会产生另一个类似的问题。当我在后台创建类似的线程时，会出现类似的问题，它会跳过数据并且 ui 没有得到更新。任何建议将不胜感激。

public class DownloadNews extends AsyncTask<Void, Void, Void>
    {

        @Override
        protected void onPreExecute() {
            shimmerFrameLayout.setVisibility(View.VISIBLE);
            relativeLayout.setVisibility(View.GONE);
            tabLayout.setVisibility(View.GONE);
        }





        @RequiresApi(api = Build.VERSION_CODES.KITKAT)
        @Override
        protected Void doInBackground(Void... voids) {
            tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
                @Override
                public void onTabSelected(TabLayout.Tab tab) {
                    viewPager.setCurrentItem(tab.getPosition());

                }

                @Override
                public void onTabUnselected(TabLayout.Tab tab) {

                }

                @Override
                public void onTabReselected(TabLayout.Tab tab) {

                }

            });
            viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
            final RequestQueue queue = Volley.newRequestQueue(Objects.requireNonNull(getContext()));
//        Checking the connection
            final StringRequest request = new StringRequest("https://www.google.com/", new Response.Listener<String>() {
                @Override
                public void onResponse(String response) {


//                instances for each required website
                    final HimalayanTimes himalayanTimes = new HimalayanTimes(getContext());
                    final GsmArena gsmArena = new GsmArena();
                    final CinemaBlend cinemaBlend = new CinemaBlend();
                    final KathmanduPost kathmanduPost = new KathmanduPost(getContext());
                    final GlobalNews globalNews =  new GlobalNews();
                    final NepaliTimes nepaliTimes = new NepaliTimes(getContext());
                    final GoalNepal goalNepal = new GoalNepal(getContext());
                    final GadgetByte gadgetByte = new GadgetByte();
                    final TechLekh techLekh = new TechLekh();
                    final OnlineKhabar onlineKhabar = new OnlineKhabar();
                    final NepaliSansar nepaliSansar = new NepaliSansar();
                    final CricketingNepal cricketingNepal = new CricketingNepal();




//                thread for each website
//                thread fot thehimalayantimes


                    Thread thread = new Thread(new Runnable() {
                        @Override
                        public void run() {
                            try  {
                                himalyannews = himalayanTimes.getNews();
                                news.addAll(himalyannews);
                                for(int i=0; i<4; i++){
                                    finalHeadlines.add(himalyannews.get(i));
                                }
                            } catch (Exception ignored) {
                            }
                        }
                    });
                    thread.start();



//                thread for gsmArena
                    Thread thread1 = new Thread(new Runnable() {
                        @Override
                        public void run() {
                            try  {
                                gsmarenanews = gsmArena.getNews();
                                news.addAll(gsmarenanews);
                                for(int i=0; i<3; i++){
                                    headlines.add(gsmarenanews.get(i));
                                }
                            } catch (Exception ignored) {
                            }
                        }
                    });
                    thread1.start();




//                thread for cinemaBlend
                    Thread thread2 = new Thread(new Runnable() {
                        @RequiresApi(api = Build.VERSION_CODES.KITKAT)
                        @Override
                        public void run() {
                            try  {
                                cinemablendnews = cinemaBlend.getNews();
                                news.addAll(cinemablendnews);
                                for(int i=0; i<4; i++){
                                    headlines.add(cinemablendnews.get(i));
                                }
                            } catch (Exception ignored) {
                            }
                        }
                    });
                    thread2.start();





//                thread for kathmanduPost
                    Thread thread3 = new Thread(new Runnable() {
                        @RequiresApi(api = Build.VERSION_CODES.KITKAT)
                        @Override
                        public void run() {
                            try {
                                kathmandupostnews = kathmanduPost.getNews();
                                news.addAll(kathmandupostnews);
                                for(int i=0; i<3; i++){
                                    finalHeadlines.add(kathmandupostnews.get(i));
                                }
                            } catch (IOException ignored) {
                            }
                        }
                    });
                    thread3.start();



//                thread for globalNews
                    Thread thread4 = new Thread(new Runnable() {
                        @Override
                        public void run() {
                            try {
                                globalnewsnews = globalNews.getNews();
                                news.addAll(globalnewsnews);
                                for(int i=0; i<5; i++){
                                    finalHeadlines.add(globalnewsnews.get(i));
                                }
                            } catch (IOException ignored) {
                            }
                        }
                    });
                    thread4.start();



//                thread for nepaliTimes
                    Thread thread5 = new Thread(new Runnable() {
                        @Override
                        public void run() {
                            try {
                                nepalitimesnews = nepaliTimes.getNews();
                                news.addAll(nepalitimesnews);
                                for(int i=0; i<3; i++){
                                    finalHeadlines.add(nepalitimesnews.get(i));
                                }
                            } catch (IOException ignored) {
                            }
                        }
                    });
                    thread5.start();


//                thread for GoalNepal
                    Thread thread6 = new Thread(new Runnable() {
                        @Override
                        public void run() {
                            try {
                                goalNepalNews = goalNepal.getNews();
                                news.addAll(goalNepalNews);
                                for (int i=0; i<4; i++){
                                    headlines.add(goalNepalNews.get(i));
                                }
                            } catch (IOException ignored) {
                            }
                        }
                    });
                    thread6.start();



//                thread for GadgetByteNepal
                    Thread thread7 = new Thread(new Runnable() {
                        @Override
                        public void run() {
                            try {
                                gadgetbytenews = gadgetByte.getNews();
                                news.addAll(gadgetbytenews);
                                for (int i=0; i<3; i++){
                                    headlines.add(gadgetbytenews.get(i));
                                }
                            } catch (IOException ignored) {
                            }
                        }
                    });
                    thread7.start();




//                thread for Techlekh
                    Thread thread8 = new Thread(new Runnable() {
                        @Override
                        public void run() {
                            try {
                                techlekhnews = techLekh.getNews();
                                news.addAll(techlekhnews);
                                for (int i=0; i<3; i++){
                                    headlines.add(techlekhnews.get(i));
                                }
                            } catch (IOException ignored) {
                            }
                        }
                    });
                    thread8.start();



                    //                thread for onlinekhabar
                    Thread thread9 = new Thread(new Runnable() {
                        @Override
                        public void run() {
                            try {
                                onlineKhabarnews = onlineKhabar.getNews();
                                news.addAll(onlineKhabarnews);
                                for (int i=0; i<4; i++){
                                    finalHeadlines.add(onlineKhabarnews.get(i));
                                }
                            } catch (IOException ignored) {
                            }
                        }
                    });
                    thread9.start();



                    //thread for nepalisansar
                    Thread thread11 = new Thread(new Runnable() {
                        @Override
                        public void run() {
                            try {
                                nepalisansarnews = nepaliSansar.getNews();
                                news.addAll(nepalisansarnews);
                                for (int i=0; i<4; i++){
                                    finalHeadlines.add(nepalisansarnews.get(i));
                                }
                            } catch (IOException ignored) {
                            }
                        }
                    });
                    thread11.start();



//                thread for cricketingNepal
                    Thread thread12 = new Thread(new Runnable() {
                        @Override
                        public void run() {
                            try {
                                cricketnews = cricketingNepal.getNews();
                                news.addAll(cricketnews);
                                for (int i=0; i<4; i++){
                                    headlines.add(cricketnews.get(i));
                                }
                            } catch (IOException ignored) {
                            }
                        }
                    });
                    thread12.start();
                    


                }
            }, new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError error) {
                    Toast.makeText(getContext(), "Internet Connection Error!", Toast.LENGTH_SHORT).show();
                    shimmerFrameLayout.setVisibility(View.GONE);
                    relativeLayout.setVisibility(View.VISIBLE);
                    tabLayout.setVisibility(View.GONE);
                }
            });
            queue.add(request);

            return null;
        }

        @Override
        protected void onPostExecute(Void aVoid) {

            tabLayout.setVisibility(View.VISIBLE);
            shimmerFrameLayout.setVisibility(View.GONE);

            for(NewsItem item : news){
                if (item.tag.contains("kathmandu"))
                    nepal.add(item);
                switch (item.tag) {
                    case "nepal":
                        nepal.add(item);
                        break;
                    case "world":
                        world.add(item);
                        break;
                    case "sports":
                        sports.add(item);
                        break;
                    case "tech":
                        tech.add(item);
                        break;
                    case "entertainment":
                        entertainment.add(item);
                        break;
                }
            }


            // putting each news item to the main container
            Collections.shuffle(headlines);
            Collections.shuffle(finalHeadlines);
            finalHeadlines.addAll(headlines);
            Collections.shuffle(nepal);
            Collections.shuffle(world);
            Collections.shuffle(sports);
            Collections.shuffle(tech);
            Collections.shuffle(entertainment);




            tab1 t1 = new tab1(finalHeadlines);
            t1.setRetainInstance(true);

            tab2 t2 = new tab2(nepal);
            t2.setRetainInstance(true);

            tab3 t3 = new tab3(world);
            t3.setRetainInstance(true);

            tab4 t4 = new tab4(sports);
            t4.setRetainInstance(true);

            tab5 t5 = new tab5(tech);
            t5.setRetainInstance(true);

            tab6 t6 = new tab6(entertainment);
            t6.setRetainInstance(true);

            shimmerFrameLayout.setVisibility(View.GONE);

            assert getFragmentManager() != null;
            pagerAdapter = new PageAdapter(finalHeadlines, nepal, world, sports, tech, entertainment, getFragmentManager(), tabLayout.getTabCount());
            viewPager.setAdapter(pagerAdapter);
        }
    }

适配器的代码与上面完全相同。