Java 如何在Android Recyclerview中显示JSON数组中包含的JSON对象

我有以下JSON数据，即一个数组中有10个对象。我在recyclerview中获取对象，没有任何错误

现在我需要做两件事：

我想在用户滚动recyclerview时显示下一页数据，即（接下来的10条记录等等）

我想在recyclerview中显示每个对象的总引号。在显示总引号时，我遇到“空对象引用上的LeadsMeta.getTotalQuotes（）”此错误

我已经在onBind-in-Adapter中对该行进行了注释

请帮我解决这两个问题。非常感谢

JSON数据

{
   "meta":{
      "code":200,
      "message":"success",
      "total_pages":247,
      "current_page":1,
      "total_items":2469,
      "total_quotes":5
   },
   "data":[
      {
         "id":"4968",
         "topic":"Topic",
         "sub_topic":"Sub Topic",
         "city":"Pune",
         "name":"Shashikant ",
         "quotes":"0",
         "credits":"10",
         "timestamp":"2021-01-05 21:53:38"
      },
      {
         "id":"4963",
         "topic":"Topic",
         "sub_topic":"Sub Topic",
         "city":"Bangalore",
         "name":"Amani",
         "quotes":"0",
         "credits":"10",
         "timestamp":"2021-01-05 20:46:03"
      },
      {
         "id":"4962",
         "topic":"Topic",
         "sub_topic":"Sub Topic",
         "city":"Delhi",
         "name":"Mechanical Engineer",
         "quotes":"0",
         "credits":"10",
         "timestamp":"2021-01-05 20:23:00"
      },
      {
         "id":"4961",
         "topic":"Topic",
         "sub_topic":"Sub Topic",
         "city":"Mumbai",
         "name":"Ankush patil",
         "quotes":"0",
         "credits":"10",
         "timestamp":"2021-01-05 20:20:20"
      },
      {
         "id":"4960",
         "topic":"Topic",
         "sub_topic":"Sub Topic",
         "city":"Delhi",
         "name":"ER Vikash Thakur",
         "quotes":"0",
         "credits":"10",
         "timestamp":"2021-01-05 20:17:32"
      },
      {
         "id":"4957",
         "topic":"Topic",
         "sub_topic":"Sub Topic",
         "city":"Kolkata",
         "name":"Shiladitya Ghosh",
         "quotes":"0",
         "credits":"10",
         "timestamp":"2021-01-05 20:09:44"
      },
      {
         "id":"4956",
         "topic":"Topic",
         "sub_topic":"Sub Topic",
         "city":"Delhi",
         "name":"Vikash",
         "quotes":"0",
         "credits":"10",
         "timestamp":"2021-01-05 20:08:44"
      },
      {
         "id":"4953",
         "topic":"Topic",
         "sub_topic":"Sub Topic",
         "city":"Rishikesh",
         "name":"Rahul",
         "quotes":"0",
         "credits":"10",
         "timestamp":"2021-01-05 19:51:17"
      },
      {
         "id":"4950",
         "topic":"Topic",
         "sub_topic":"Sub Topic",
         "city":"Pune",
         "name":"Abhishek",
         "quotes":"0",
         "credits":"10",
         "timestamp":"2021-01-05 19:43:27"
      },
      {
         "id":"4949",
         "topic":"Topic",
         "sub_topic":"Sub Topic",
         "city":"Chandigarh ",
         "name":"K Singh ",
         "quotes":"0",
         "credits":"10",
         "timestamp":"2021-01-05 19:40:36"
      }
   ]
}

我的片段：

public class LeadsFragment extends Fragment {

    RecyclerView recyclerView;
    RecyclerView.LayoutManager layoutManager;
    private static final String url = "myurl";

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        View view = inflater.inflate(R.layout.fragment_leads, container, false);

        recyclerView = view.findViewById(R.id.recyclerview);

        StringRequest stringRequest = new StringRequest(url, new Response.Listener<String>() {
            @Override
            public void onResponse(String response) {

                GsonBuilder gsonBuilder = new GsonBuilder();
                Gson gson = gsonBuilder.create();
                LeadModel leadsModelList = gson.fromJson(response, LeadModel.class);

                recyclerView.setHasFixedSize(true);
                layoutManager = new LinearLayoutManager(getActivity());
                recyclerView.setLayoutManager(layoutManager);
                LeadsAdapter leadsAdapter = new LeadsAdapter(getContext(), leadsModelList, recyclerView);
                recyclerView.setAdapter(leadsAdapter);

            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {

                Toast.makeText(getContext(), error.toString(), Toast.LENGTH_SHORT).show();

            }
        });

        RequestQueue queue = Volley.newRequestQueue(getContext());
        queue.add(stringRequest);

        return view;
    }
}

数据类

public class LeadsData {

    @SerializedName("id")
    @Expose
    private String id;
    @SerializedName("topic")
    @Expose
    private String topic;
    @SerializedName("sub_topic")
    @Expose
    private String subTopic;
    @SerializedName("city")
    @Expose
    private String city;
    @SerializedName("name")
    @Expose
    private String name;
    @SerializedName("quotes")
    @Expose
    private String quotes;
    @SerializedName("credits")
    @Expose
    private String credits;
    @SerializedName("timestamp")
    @Expose
    private String timestamp;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getTopic() {
        return topic;
    }

    public void setTopic(String topic) {
        this.topic = topic;
    }

    public String getSubTopic() {
        return subTopic;
    }

    public void setSubTopic(String subTopic) {
        this.subTopic = subTopic;
    }

    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getQuotes() {
        return quotes;
    }

    public void setQuotes(String quotes) {
        this.quotes = quotes;
    }

    public String getCredits() {
        return credits;
    }

    public void setCredits(String credits) {
        this.credits = credits;
    }

    public String getTimestamp() {
        return timestamp;
    }

    public void setTimestamp(String timestamp) {
        this.timestamp = timestamp;
    }

}

“meta”对象的SerializedName在LeadModel类中应为“meta”

public class LeadModel {
     
    //@SerializedName("leadsMeta")

    @SerializedName("meta")
    @Expose
    private LeadsMeta leadsMeta;}

我想显示下一页数据

请在您的recyclerView上使用

recyclerView.addOnScrollListener

。当用户滚动并到达最后一项时，您需要加载更多的10项并将列表附加到现有列表中

public class LeadsFragment extends Fragment {

    RecyclerView recyclerView;
    RecyclerView.LayoutManager layoutManager;
    private static final String url = "myurl";
    boolean isLoading = false; // For Tracking  


    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    ......
    ........
    recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
            @Override
            public void onScrollStateChanged(@NonNull RecyclerView recyclerView, int newState) {
                super.onScrollStateChanged(recyclerView, newState);
            }

            @Override
            public void onScrolled(@NonNull RecyclerView recyclerView, int dx, int dy) {
                super.onScrolled(recyclerView, dx, dy);
                LinearLayoutManager linearLayoutManager = (LinearLayoutManager) recyclerView.getLayoutManager();

                if (!isLoading) {
                    if (linearLayoutManager != null && linearLayoutManager.findLastCompletelyVisibleItemPosition() == yourList.size() - 1) {
                        // Last item reached
                        loadMore(); // Note this method
                        isLoading = true;
                    }
                }

            }
        });

 private void loadMore() {
        // Make http Request
        // append the new data to LeadsData
        // notifyAdapter items changed
        // set isLoading = false
    }

我在一个空对象引用上面临“LeadsMeta.getTotalQuotes（）”

这是因为LeadModel中的序列化名称应该与json一致

@SerializedName("meta")

---

对于您的第一个问题：

你需要检查代码。在MainActivity.java类中，有一个方法loadMore（）。在您的情况下，您需要执行API调用来加载10个以上的项目，然后通知您的适配器您有新的项目，它将在您的列表中加载它们。这就是你如何用无止境的物品实现你的回收视图

对于第二个问题：

您应该将@SerializedName中的leadsMeta更改为meta。 这是您编辑的课程：

public class LeadModel {

    @SerializedName("meta")
    @Expose
    private LeadsMeta leadsMeta;
    @SerializedName("data")
    @Expose
    private List<LeadsData> data = null;

    public LeadsMeta getMeta() {
        return leadsMeta;
    }

    public void setMeta(LeadsMeta leadsMeta) {
        this.leadsMeta = leadsMeta;
    }

    public List<LeadsData> getData() {
        return data;
    }

    public void setData(List<LeadsData> data) {
        this.data = data;
    }

}

公共类模型{
@序列化名称（“元”）
@暴露
私人铅塔铅塔；
@SerializedName（“数据”）
@暴露
私有列表数据=null；
公众领袖梅塔·格梅塔（）{
回程导线数据；
}
公共无效设置元（LeadsMeta LeadsMeta）{
this.leadsMeta=leadsMeta；
}
公共列表getData（）{
返回数据；
}
公共无效设置数据（列表数据）{
这个数据=数据；
}
}

我正在分享关于我在回答中分享的代码的教程。快乐编码：）我用@SerializedName（“meta”）的名字犯了一个多么愚蠢的错误。。。谢谢你，做了所有的事。但有一件事还不清楚。如何追加数据并通知适配器//将新数据追加到LeadData//notifyAdapter项已更改

public class LeadsFragment extends Fragment {

    RecyclerView recyclerView;
    RecyclerView.LayoutManager layoutManager;
    private static final String url = "myurl";
    boolean isLoading = false; // For Tracking  


    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    ......
    ........
    recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
            @Override
            public void onScrollStateChanged(@NonNull RecyclerView recyclerView, int newState) {
                super.onScrollStateChanged(recyclerView, newState);
            }

            @Override
            public void onScrolled(@NonNull RecyclerView recyclerView, int dx, int dy) {
                super.onScrolled(recyclerView, dx, dy);
                LinearLayoutManager linearLayoutManager = (LinearLayoutManager) recyclerView.getLayoutManager();

                if (!isLoading) {
                    if (linearLayoutManager != null && linearLayoutManager.findLastCompletelyVisibleItemPosition() == yourList.size() - 1) {
                        // Last item reached
                        loadMore(); // Note this method
                        isLoading = true;
                    }
                }

            }
        });

 private void loadMore() {
        // Make http Request
        // append the new data to LeadsData
        // notifyAdapter items changed
        // set isLoading = false
    }

@SerializedName("meta")

public class LeadModel {

    @SerializedName("meta")
    @Expose
    private LeadsMeta leadsMeta;
    @SerializedName("data")
    @Expose
    private List<LeadsData> data = null;

    public LeadsMeta getMeta() {
        return leadsMeta;
    }

    public void setMeta(LeadsMeta leadsMeta) {
        this.leadsMeta = leadsMeta;
    }

    public List<LeadsData> getData() {
        return data;
    }

    public void setData(List<LeadsData> data) {
        this.data = data;
    }

}