數據未綁定到android recyclerview

Question

我是Android新手。 我正在嘗試使用Github api下載數據並在無限滾動的RecyclerView中顯示，已解析JSON數據，但是不知何故該數據未附加到recyclerview。 這是下面的代碼：

Developer_RV_Adapter.java
package com.davidshare.githubdevelopers;

import android.content.Context;
import android.content.Intent;
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.ImageView;
import android.widget.ProgressBar;
import android.widget.TextView;

import com.squareup.picasso.Picasso;

import java.util.List;

/**
 * Created by GemShare on 9/6/2017.
 */
public class Developer_RV_Adapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
    private final int VIEW_TYPE_ITEM = 0;
    private final int VIEW_TYPE_LOADING = 1;
    private OnLoadMoreListener mOnLoadMoreListener;
    private boolean isLoading;
    private int visibleThreshold = 10;
    private int lastVisibleItem, totalItemCount;
    private List<Developer> developerList;
    Context context;
    RecyclerView recyclerView;

    public Developer_RV_Adapter(Context context, List<Developer> developerList, RecyclerView recyclerView) {
        this.developerList = developerList;
        this.context = context;
        this.recyclerView = recyclerView;

        final LinearLayoutManager linearLayoutManager = (LinearLayoutManager) recyclerView.getLayoutManager();
        recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
            @Override
            public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
                super.onScrolled(recyclerView, dx, dy);
                totalItemCount = linearLayoutManager.getItemCount();
                lastVisibleItem = linearLayoutManager.findLastVisibleItemPosition();
                if(!isLoading && totalItemCount<=(lastVisibleItem+visibleThreshold)){
                    if(mOnLoadMoreListener!=null){
                        mOnLoadMoreListener.onLoadMore();
                    }
                    isLoading = true;
                }
            }
        });
    }

    public void setmOnLoadMoreListener(OnLoadMoreListener mOnLoadMoreListener){
        this.mOnLoadMoreListener = mOnLoadMoreListener;
    }

    @Override
    public  int getItemViewType(int position){
        return developerList.get(position) == null? VIEW_TYPE_LOADING : VIEW_TYPE_ITEM;
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        if(viewType == VIEW_TYPE_ITEM){
            View developerView = LayoutInflater.from(context).inflate(R.layout.developer_list_item, parent, false);
            return new DeveloperViewHolder(developerView);
        }else if(viewType== VIEW_TYPE_LOADING){
            View loadingView = LayoutInflater.from(context).inflate(R.layout.progress_bar_item, parent, false);

            return new ProgressViewHolder(loadingView);
        }
        return null;
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        Log.w("binder function", "Just entered the binder");
        Developer developer = developerList.get(position);
        if(holder instanceof DeveloperViewHolder){
            DeveloperViewHolder developerViewHolder = (DeveloperViewHolder) holder;
            developerViewHolder.gitNameTv.setText(developer.getGitUsername());
            Log.w("binder ", developer.getGitProfileUrl());
            developerViewHolder.gitUrlTv.setText(developer.getGitProfileUrl());
            developerViewHolder.gitPicUrlTv.setText(developer.getGitProfilePicUrl());
            Log.w("profile pic", developer.getGitProfilePicUrl());
            Picasso.with(developerViewHolder.gitNameTv.getContext()).load(developer.getGitProfilePicUrl()).transform(new RoundedImage(2)).fit().centerCrop().into(developerViewHolder.profilePicImgV);
        }else if (holder instanceof ProgressViewHolder) {
            ProgressViewHolder loadingViewHolder = (ProgressViewHolder) holder;
            loadingViewHolder.loadingProgress.setIndeterminate(true);
        }
    }

    @Override
    public int getItemCount() {
        return developerList == null ? 0 : developerList.size();
    }

    public void setLoaded() {
        isLoading = false;
    }

    public class DeveloperViewHolder extends RecyclerView.ViewHolder{
        TextView gitNameTv;
        TextView gitUrlTv;
        ImageView profilePicImgV;
        TextView gitPicUrlTv;

        public DeveloperViewHolder(final View itemView) {
            super(itemView);
            gitNameTv = (TextView) itemView.findViewById(R.id.developerName);
            gitUrlTv = (TextView) itemView.findViewById(R.id.developerUrl);
            profilePicImgV = (ImageView) itemView.findViewById(R.id.developerPic);
            gitPicUrlTv = (TextView) itemView.findViewById(R.id.developerPicUrl);
            itemView.setOnClickListener(new View.OnClickListener(){
                @Override
                public void onClick(View v){
                    Intent i = new Intent(itemView.getContext(), Profile.class);
                    i.putExtra("profile_name", gitNameTv.getText().toString());
                    i.putExtra("profile_url", gitUrlTv.getText().toString());
                    i.putExtra("profile_pic_url", gitPicUrlTv.getText().toString());
                    v.getContext().startActivity(i);
                }
            });
        }
    }

    public static class ProgressViewHolder extends RecyclerView.ViewHolder{
        public ProgressBar loadingProgress;

        public ProgressViewHolder(View itemView) {
            super(itemView);
            loadingProgress = (ProgressBar) itemView.findViewById(R.id.loading_progress_bar);
        }
    }
}



DeveloperList.java
package com.davidshare.githubdevelopers;

import android.app.ProgressDialog;
import android.os.Handler;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;

import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.StringRequest;
import com.android.volley.toolbox.Volley;

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

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

public class DeveloperList extends AppCompatActivity {
    List<Developer> developerList;
    Developer_RV_Adapter developer_rv_adapter;
    Developer developer;
    RecyclerView developerRV;
    private static final String GIT_BASE_URL = "https://api.github.com/search/users?q=location:";
    private static int page = 1;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_developer_list);
        developerRV = (RecyclerView) findViewById(R.id.developer_rv);
        developerRV.setLayoutManager(new LinearLayoutManager(this));
        developerList = new ArrayList<>();
        getDevelopersData(prepareQuery("java", "lagos", page));
        developer_rv_adapter = new Developer_RV_Adapter(DeveloperList.this, developerList, developerRV);
        developerRV.setAdapter(developer_rv_adapter);
        developer_rv_adapter.setmOnLoadMoreListener(new OnLoadMoreListener() {
            @Override
            public void onLoadMore() {
                developerList.add(null);
                developer_rv_adapter.notifyItemInserted(developerList.size()-1);
                new Handler().postDelayed(new Runnable() {
                    @Override
                    public void run() {
                        developerList.remove(developerList.size()-1);
                        developer_rv_adapter.notifyItemRemoved(developerList.size());
                        getDevelopersData(prepareQuery("java", "lagos", page));
                        developer_rv_adapter.notifyDataSetChanged();
                        developer_rv_adapter.setLoaded();
                    }
                }, 5000);
            }
        });
    }

getDevelopersData方法使用volley查詢github api並將JSON響應解析為一個List

    public void getDevelopersData(String requestUrl) {
        StringRequest jsonSringRequest = new StringRequest(Request.Method.GET, requestUrl, new Response.Listener<String>() {
            @Override
            public void onResponse(String jsonResponse) {
                try {
                    JSONObject gitJSONOBject = new JSONObject(jsonResponse);
                    JSONArray gitItemsArray = gitJSONOBject.getJSONArray("items");

                    for (int i = 0; i < gitItemsArray.length(); i++) {
                        JSONObject developerObject = gitItemsArray.getJSONObject(i);
                        developer = new Developer(developerObject.getString("login"),
                                developerObject.getString("html_url"),
                                developerObject.getString("avatar_url"));
                        developerList.add(developer);
                        Log.w("developer_data ", developer.getGitUsername());
                    }
                    Log.w("JSON DATA", "getting the json data");
                } catch (JSONException e) {
                    e.printStackTrace();
                }
            }
        },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError volleyError) {
                        Log.e("Volley error", volleyError.getMessage());
                    }
                });

        RequestQueue requestQueue = Volley.newRequestQueue(this);
        requestQueue.add(jsonSringRequest);
    }
//get the location and language and the page of the api data you want to load
    private String prepareQuery(String language, String location, int page){
        this.page++;
        String queryUrl = GIT_BASE_URL+location+"+language:"+language+"&page="+page+"&per_page=50";
        Log.w("Query URL = > ", queryUrl);
        return queryUrl;
    }

}

誰能幫我這個？

Answer 1

嘗試將數據添加到數組列表后在getDevelopersData（）中通知適配器，例如添加以下行developer_rv_adapter.notifyDataSetChanged（）;

Answer 2

代替使用notifyItemInserted（）插入

notifyItemRangedChanged(fromIndex,toIndex);

這將通知適配器整個數據中的某些數據集已更改，並告訴適配器適配器應刷新數據並將其重新裝入到傳遞自方法的fromIndex到toIndex的recyclerView中。

如果所有數據都已更改，請使用：

notifyDataSetChanged();

如果僅更改一個dataItem，則使用：

notifyItemChanged(dataPosition);

我也認為此陳述引起了問題。請嘗試刪除此陳述，然后再次檢查。

new Handler().postDelayed(new Runnable() {
                @Override
                public void run() {
                    developerList.remove(developerList.size()-1);
                    developer_rv_adapter.notifyItemRemoved(developerList.size());
                    getDevelopersData(prepareQuery("java", "lagos", page));
                    developer_rv_adapter.notifyDataSetChanged();
                    developer_rv_adapter.setLoaded();
                }
            }, 5000);

Answer 3

通過添加developer_rv_adapter.notifyDataSetChanged（）;解決了該問題。 就在developerList.add（developer）;之下 這會通知適配器新項目已添加到列表中。