如何在 RecyclerView 中使用 JsonArray 存储对象后解析 Android JsonObject 并存储它

Question

我试图解析Json，如下所示：

     {
      "status": "ok",
      "feed": {
        "title": "title1",
        "link": "http://www.link/",
        "author": "",
        "description": "desc",
        "image": ""
      },
      "items": [
        {
          "title": "something",
          "link": "something",
          "guid": "something",
          "pubDate": "date",
          "categories": [],
          "author": "",
          "thumbnail": "",
          "description": null,
          "content": null
        },
...
...

我从response 得到了预期的结果，但这不是重点。这就是我所做的：

try {

            JSONObject response = new JSONObject(result);

            JSONObject feed_object = response.getJSONObject("feed");
            PostItems item = new PostItems();
            item.setAuthor(feed_object.getString("title"));

            JSONArray items_arr = response.getJSONArray("items");
            for (int i = 0; i < items_arr.length(); i++) {
                JSONObject post = items_arr.getJSONObject(i);

                item.setTitle(post.getString("title"));
                item.setDate(post.getString("pubDate")); // As expected results

                feedItem.add(item);
            }

        }

关键是，如果我存储（first object）就像我到目前为止所做的上述代码，RecyclerView 正在显示项目但没有在项目内设置正确的title 和date。

如果我将它存储在数组中，然后在数组内部（对于array）和array 之外设置一个，它只会显示如下错误：

java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.String.length()' on a null object reference
               at java.io.StringReader.<init>(StringReader.java:47)
               at android.text.HtmlToSpannedConverter.convert(Html.java:449)
               at android.text.Html.fromHtml(Html.java:136)
               at android.text.Html.fromHtml(Html.java:99)
               at client.com.news.RecyclerViews.MainSanjeshRecyclerView.MyRecyclerAdapter.onBindViewHolder(MyRecyclerAdapter.java:34)
               at client.com.news.RecyclerViews.MainSanjeshRecyclerView.MyRecyclerAdapter.onBindViewHolder(MyRecyclerAdapter.java:14)
               at android.support.v7.widget.RecyclerView$Adapter.onBindViewHolder(RecyclerView.java:5465)
               at android.support.v7.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:5498)
               at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:4735)
               at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:4611)
               at android.support.v7.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:1988)
               at android.support.v7.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1384)
               at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1347)
               at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:574)
               at android.support.v7.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:3026)
               at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:2903)
               at android.support.v7.widget.RecyclerView.onLayout(RecyclerView.java:3277)
               at android.view.View.layout(View.java:16630)
               at android.view.ViewGroup.layout(ViewGroup.java:5437)
               at android.support.v4.widget.SwipeRefreshLayout.onLayout(SwipeRefreshLayout.java:596)
               at android.view.View.layout(View.java:16630)
               at android.view.ViewGroup.layout(ViewGroup.java:5437)
               at android.support.v4.view.ViewPager.onLayout(ViewPager.java:1684)
               at android.view.View.layout(View.java:16630)
               at android.view.ViewGroup.layout(ViewGroup.java:5437)
               at android.support.design.widget.HeaderScrollingViewBehavior.layoutChild(HeaderScrollingViewBehavior.java:122)
               at android.support.design.widget.ViewOffsetBehavior.onLayoutChild(ViewOffsetBehavior.java:42)
               at android.support.design.widget.AppBarLayout$ScrollingViewBehavior.onLayoutChild(AppBarLayout.java:1139)
               at android.support.design.widget.CoordinatorLayout.onLayout(CoordinatorLayout.java:810)
               at android.view.View.layout(View.java:16630)
               at android.view.ViewGroup.layout(ViewGroup.java:5437)
               at android.widget.FrameLayout.layoutChildren(FrameLayout.java:336)
               at android.widget.FrameLayout.onLayout(FrameLayout.java:273)
               at android.view.View.layout(View.java:16630)
               at android.view.ViewGroup.layout(ViewGroup.java:5437)
               at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1743)
               at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1586)
               at android.widget.LinearLayout.onLayout(LinearLayout.java:1495)
               at android.view.View.layout(View.java:16630)
               at android.view.ViewGroup.layout(ViewGroup.java:5437)
               at android.widget.FrameLayout.layoutChildren(FrameLayout.java:336)
               at android.widget.FrameLayout.onLayout(FrameLayout.java:273)
               at android.view.View.layout(View.java:16630)
               at android.view.ViewGroup.layout(ViewGroup.java:5437)
               at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1743)
               at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1586)
               at android.widget.LinearLayout.onLayout(LinearLayout.java:1495)
               at android.view.View.layout(View.java:16630)
               at android.view.ViewGroup.layout(ViewGroup.java:5437)
               at android.widget.FrameLayout.layoutChildren(FrameLayout.java:336)
               at android.widget.FrameLayout.onLayout(FrameLayout.java:273)
               at com.android.internal.policy.PhoneWindow$DecorView.onLayout(PhoneWindow.java:2678)
               at android.view.View.layout(View.java:16630)
               at android.view.ViewGroup.layout(ViewGroup.java:5437)
               at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2171)
            at android.vi

第二次尝试：

try {

                JSONObject response = new JSONObject(result);

                JSONObject feed_object = response.getJSONObject("feed");
                PostItems item = new PostItems();
                item.setAuthor(feed_object.getString("title"));

                JSONArray items_arr = response.getJSONArray("items");
                for (int i = 0; i < items_arr.length(); i++) {
                    JSONObject post = items_arr.getJSONObject(i);
                    PostItems item2 = new PostItems();
                    item2.setTitle(post.getString("title"));
                    item2.setDate(post.getString("pubDate"));

                    feedItem.add(item2);
                }
                feedItem.add(item);
            }

实际上，我已经尝试了任何你能想象到的东西，并在 stackoverflow 上看到了任何问题，但我找不到类似这样的问题，但是有一次，只显示一个项目而没有来自对象的正确数据，有一次没有显示来自Array 的正确数据。

任何帮助都会很棒。

Answer 1

您试图在每个项目中使用getAuthor()，但显然它仅用于ArrayList 中的一个（第一个）项目。当它没有任何值时，它返回null，结果为NullPointerException。每次迭代都应该创建新对象。

动起来

PostItems item = new PostItems();
item.setAuthor(feed_object.getString("title"));

在for 循环内。

编辑

try {
    JSONObject response = new JSONObject(result);

    JSONObject feed_object = response.getJSONObject("feed");

    JSONArray items_arr = response.getJSONArray("items");
    for (int i = 0; i < items_arr.length(); i++) {
        JSONObject post = items_arr.getJSONObject(i);
        PostItems item = new PostItems();
        item.setAuthor(feed_object.getString("title")); // being fetched from top node
        item.setTitle(post.getString("title")); // being fetched from array
        item.setDate(post.getString("pubDate")); // being fetched from array

        feedItem.add(item);
    }

}