在 Firebase 中存储来自 NewsAPI 的 JSON 数组

Question

我使用 volley 来解析来自 newsAPI.org 的新闻数据。我想将响应保存到 Firebase 以供离线查看和持久化。

这是来自 API 的示例响应：

articles: [
{
     author: "Megan Rose Dickey",
     title: "Ojo wants to be the electric scooter for commuters, but...",
     description: "Commuting in a busy city like San Francisco can be 
     annoying..",
     url: "https://techcrunch.com/2017/08/23/ojo-wants-to-be-the-electric-
     scooter-for-commuters-but-its-not-there-yet/",
     urlToImage: "https://img.vidible.tv/prod/2017",
     publishedAt: "2017-08-23T21:19:56Z"
},
{
     author: "Katie Roof",
     title: "Pishevar intervenes in Benchmark-Kalanick lawsuit",
     description: "Early Uber investor and former board member Shervin 
     Pishevar is speaking out against Benchmark again..",
     url: "https://techcrunch.com/2017/08/24/pishevar-sends-another-letter-
     to-uber-board-about-benchmark/",
     urlToImage:"https://tctechcrunch2011.files.wordpress.com/",
     publishedAt: "2017-08-24T22:49:59Z"
},

articles 数组中总共有 5 个对象。 我想将每个对象存储在 Firebase 数据库中。这是我尝试过的：

StringRequest stringRequest = new StringRequest(Request.Method.GET, Constants.NEWS_ENDPOINT,
            new Response.Listener<String>() {
                @Override
                public void onResponse(String response) {
                    if (response != null){
                        Log.d(TAG, "News Api Response is: \t" + response.toString());
                        try {
                            JSONObject jsonObject = new JSONObject(response);
                            JSONArray articles = jsonObject.getJSONArray("articles");
                            for (int i = 0; i < articles.length(); i++){
                                JSONObject items = articles.getJSONObject(i);

                                final String title_news = items.getString("title");
                                final String desc_news = items.getString("description");
                                final String urlImg = items.getString("urlToImage");
                                final String author_news = items.getString("author");
                                final String url = items.getString("url");
                                final String publishedAt = items.getString("publishedAt");

                                NewsItem newsItem = new NewsItem(author_news, title_news, desc_news, url, urlImg, publishedAt);
                                itemList.add(newsItem);

                                /**
                                 *  Save JSON Results to Firebase
                                 * */

                                for (int k = 0; k < articles.length(); k++){
                                    HashMap hashMap = new HashMap();

                                    hashMap.put("newsTitle", title_news);
                                    hashMap.put("newsDesc", desc_news);
                                    hashMap.put("newsImageUrl", urlImg);
                                    hashMap.put("newsAuthor", author_news);
                                    hashMap.put("newsUrl", url);
                                    hashMap.put("newsDate", publishedAt);

                                    newsRootRef.setValue(hashMap);
                                }

当我检查控制台时，它只保存一个对象，最后一个对象是这样的：

我想将所有对象按原样存储在响应数组中并稍后检索它们。还有其他方法可以做到这一点吗？谢谢，很抱歉发了这么长的帖子。

Answer 1

在这种情况下，您需要使用 push() 来存储数据。否则，您只是在每次迭代时替换引用处的数据。这就是为什么似乎只存储最后一条记录的原因。尝试更改此行：

newsRootRef.setValue(hashMap);

...进入这个：

newsRootRef.push().setValue(hashMap);

为避免重复条目，我建议您从 Firebase 获取所有条目并将 url 属性（因为该属性似乎是唯一的）缓存在 HashSet 中。然后你可以像这样修改你的代码：

if (!urlSet.contains(url)) {
    HashMap hashMap = new HashMap();
    hashMap.put("newsTitle", title_news);
    hashMap.put("newsDesc", desc_news);
    hashMap.put("newsImageUrl", urlImg);
    hashMap.put("newsAuthor", author_news);
    hashMap.put("newsUrl", url);
    hashMap.put("newsDate", publishedAt);
    newsRootRef.push(),setValue(hashMap);
}

当然，您需要先填充 HashSet，所以我建议您这样做：

    final Set<String> urlSet = new HashSet<>();

    newsRootRef.addChildEventListener(new ChildEventListener() {
        int i = 0;

        @Override
        public void onChildAdded(DataSnapshot dataSnapshot, String s) {

            urlSet.add(dataSnapshot.getValue(String.class));
            if (i++ == dataSnapshot.getChildrenCount()) {

                ...
                ...your code...
                StringRequest stringRequest = new StringRequest(Request.Method.GET, Constants.NEWS_ENDPOINT,
                        new Response.Listener<String>() {
                            @Override
                            public void onResponse(String response) {

                ...
                ...

            }

        }

        @Override
        public void onChildChanged(DataSnapshot dataSnapshot, String s) {
        }

        @Override
        public void onChildRemoved(DataSnapshot dataSnapshot) {
        }

        @Override
        public void onChildMoved(DataSnapshot dataSnapshot, String s) {
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {
        }
    });