java - 如何使用 swipeRefreshLayout 更新 fragment 中的新 json 数据

Question

在这个 fragment 中，我向服务器发送了一个带 volley 的 jsonRequest。并且我将 swipeRefreshLayout 设置为此 fragment ，我只想加载新的 json 数据，但是当我在 onRefresh()< 上使用 sendJsonRequest() 方法时 为 recyclerView 启用所有 json 数据:

这是我的 fragment 代码:

package ghandak.ghandshekan.com.ghandak.fragments;

import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v4.widget.SwipeRefreshLayout;
import android.support.v4.widget.SwipeRefreshLayout.OnRefreshListener;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Toast;

import com.android.volley.Request;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.JsonArrayRequest;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.util.ArrayList;
import java.util.List;

import ghandak.ghandshekan.com.ghandak.R;
import ghandak.ghandshekan.com.ghandak.adapters.PostRecyclerAdapter;
import ghandak.ghandshekan.com.ghandak.app.AppController;
import ghandak.ghandshekan.com.ghandak.models.PostData;

/**
 * Created by imajid on 12/19/2015.
 */
public class TabFragment3 extends Fragment implements OnRefreshListener{
    private RecyclerView allContentRecyclerView;
    private String url  = "http://kakdo.herokuapp.com/api/news/?format=json";
    private List<PostData> postDataList = new ArrayList<PostData>();
    private SwipeRefreshLayout swipeRefreshLayout;

    //====================================================================================== onCreateView
    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.tab_fragment_3 , container , false);
        allContentRecyclerView = (RecyclerView)view.findViewById(R.id.xmlRecyclerViewtabFragment3);
        allContentRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
        swipeRefreshLayout = (SwipeRefreshLayout)view.findViewById(R.id.xml_swipe_refresh_layout_tab_fragment_3);
        swipeRefreshLayout.setOnRefreshListener(this);
        swipeRefreshLayout.setColorSchemeResources(android.R.color.holo_blue_bright,
                android.R.color.holo_green_light,
                android.R.color.holo_orange_light,
                android.R.color.holo_red_light);
        //swipeRefreshLayout.setColorSchemeColors();



        return view;
    }

    //====================================================================================== onCreate


    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        sendJsonRequest();
    }

    //====================================================================================== sendjsonRequest
    private void sendJsonRequest() {

        JsonArrayRequest request = new JsonArrayRequest(Request.Method.GET, url, (String) null, new Response.Listener<JSONArray>() {
            @Override
            public void onResponse(JSONArray response) {
                parseJsonResponse(response);
                //==========setting adapter to the recyclerview  <==
                allContentRecyclerView.setAdapter(new PostRecyclerAdapter(getActivity() ,postDataList));
            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {

            }
        });

        AppController.getInstance().addToRequestQueue(request);

    }

    //====================================================================================== parsjsonResponse()
    private void parseJsonResponse(JSONArray response) {
        if(response == null){
            Toast.makeText(getActivity(), "ریسپانس خالی هستش", Toast.LENGTH_SHORT).show();
            return;
        }else {
            Log.d("parsejsonresponse", "response khali nist");
            for (int i = 0 ; i < response.length()  ; i++ ){

                try {

                    //Toast.makeText(getActivity(), "ریسپانس میگیرم ", Toast.LENGTH_SHORT).show();
                    JSONObject currentPost = response.getJSONObject(i);
                    //Log.d("currentPost", "currentPost ro gereftam");

                    PostData postData = new PostData();
                    postData.setTitle(currentPost.getString("title"));
                    //Toast.makeText(getActivity() , currentPost.getString("title") , Toast.LENGTH_SHORT).show();
                    postData.setCreate(currentPost.getString("create"));

                    postDataList.add(postData);

                } catch (JSONException e) {
                    e.printStackTrace();
                }

            }
        }

    }

    @Override
    public void onRefresh() {
        sendJsonRequest();
        swipeRefreshLayout.setRefreshing(false);

    }
}

现在我的问题是在 OnRefresh 方法中，我可以写什么来只加载新的 json 数据，而不是所有现有的 json。

Answer 1

在你的代码中添加这一行

  postDataList.clear(); in your code given in bellow.

更新:

           @Override
    public void onResponse(JSONArray response) {
        if(response == null )
            return;
        postDataList.clear();
        parseJsonResponse(response);
        //==========setting adapter to the recyclerview  <==
        allContentRecyclerView.setAdapter(new PostRecyclerAdapter(getActivity() ,postDataList));
    }

注意:当您在代码中创建任何类型的列表最多创建一次适配器实例时，更改列表数据后您只需调用“adapterInstance.notifyDataSetChange();”这是最好的做法，而不是每次刷新列表项时都创建列表，更多信息检查 here