java - 在 Recycler View 中实现无限滚动

Question

我有一个 Recycler View，它使用 AsyncTask 来填充 UI。

目前它从数据库中检索所有数据并一次性显示出来，但是

我只想一次性检索 15 条记录，在滚动结束后我想加载更多 15 条记录等等...有人可以帮忙吗？我粘贴了下面的代码:

FeedActivity.java

package com.bbau.ankit.test_splash;

import android.app.Activity;
import android.graphics.Color;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.Window;

import com.yqritc.recyclerviewflexibledivider.HorizontalDividerItemDecoration;

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

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;import java.net.URL;
import java.util.ArrayList;
import java.util.List;

/**
 * Created by Ankit on 8/14/2015.
 */
public class FeedListActivity extends Activity {
    private static final String TAG = "RecyclerViewExample";

    private List<FeedItem> feedItemList = new ArrayList<FeedItem>();

    private RecyclerView mRecyclerView;

    private MyRecyclerAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        /* Allow activity to show indeterminate progressbar */
        requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);

        setContentView(R.layout.news);

        /* Initialize recyclerview */
        mRecyclerView = (RecyclerView) findViewById(R.id.recycler_view);
        mRecyclerView.addItemDecoration(new HorizontalDividerItemDecoration.Builder(this).color(Color.BLACK).build());
        mRecyclerView.setLayoutManager(new LinearLayoutManager(this));

        /*Downloading data from below url*/
        final String url = "http://192.168.170.72/bbau_news.php?before=1&after=5";
        new AsyncHttpTask().execute(url);

    }

    public class AsyncHttpTask extends AsyncTask<String, Void, Integer> {

        @Override
        protected void onPreExecute() {
            setProgressBarIndeterminateVisibility(true);
        }

        @Override
        protected Integer doInBackground(String... params) {
            InputStream inputStream = null;
            Integer result = 0;
            HttpURLConnection urlConnection = null;

            try {
                /* forming th java.net.URL object */
                URL url = new URL(params[0]);

                urlConnection = (HttpURLConnection) url.openConnection();

                /* for Get request */
                urlConnection.setRequestMethod("GET");

                int statusCode = urlConnection.getResponseCode();

                /* 200 represents HTTP OK */
                if (statusCode ==  200) {

                    BufferedReader r = new BufferedReader(new InputStreamReader(urlConnection.getInputStream()));
                    StringBuilder response = new StringBuilder();
                    String line;
                    while ((line = r.readLine()) != null) {
                        response.append(line);
                    }

                    parseResult(response.toString());
                    result = 1; // Successful
                }else{
                    result = 0; //"Failed to fetch data!";
                }

            } catch (Exception e) {
                Log.d(TAG, e.getLocalizedMessage());
            }

            return result; //"Failed to fetch data!";
        }

        @Override
        protected void onPostExecute(Integer result) {

            setProgressBarIndeterminateVisibility(false);

            /* Download complete. Lets update UI */
            if (result == 1) {
                adapter = new MyRecyclerAdapter(FeedListActivity.this, feedItemList);
                mRecyclerView.setAdapter(adapter);
            } else {
                Log.e(TAG, "Failed to fetch data!");
            }
        }
    }

    private void parseResult(String result) {
        try {
            JSONObject response = new JSONObject(result);
            JSONArray posts = response.optJSONArray("NEWS");

            /*Initialize array if null*/
            if (null == feedItemList) {
                feedItemList = new ArrayList<FeedItem>();
            }

            for (int i = 0; i < posts.length(); i++) {
                JSONObject post = posts.optJSONObject(i);

                FeedItem item = new FeedItem();
                item.setTitle(post.optString("news_desc"));
                item.setDescription(post.optString("Date"));
                item.setUrl(post.optString("News"));
                feedItemList.add(item);
            }
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }

}

MyRecyclerAdapter.java

package com.bbau.ankit.test_splash;

import android.content.Context;
import android.content.Intent;
import android.support.v7.widget.RecyclerView;
import android.text.Html;
import android.text.style.AlignmentSpan;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.widget.Toast;

import org.w3c.dom.Text;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.List;

/**
 * Created by Ankit on 8/14/2015.
 */
public class MyRecyclerAdapter extends RecyclerView.Adapter<FeedListRowHolder> {



    private List<FeedItem> feedItemList;

    private Context mContext;

    public MyRecyclerAdapter(Context context, List<FeedItem> feedItemList) {
        this.feedItemList = feedItemList;
        this.mContext = context;
    }

    @Override
    public FeedListRowHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
        View v = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.list_row, null);
        FeedListRowHolder mh = new FeedListRowHolder(v);
        mh.relativeLayout.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Log.d("List Size", Integer.toString(getItemCount()));
                TextView redditUrl = (TextView) v.findViewById(R.id.url);
                String postUrl = redditUrl.getText().toString();
                Log.d("The URL:", postUrl);
                Intent intent = new Intent(mContext, WebViewActivity.class);
                intent.putExtra("url", postUrl);
                mContext.startActivity(intent);
            }
        });

        return mh;
    }

    @Override
    public void onBindViewHolder(FeedListRowHolder feedListRowHolder, int i) {
        final FeedItem feedItem = feedItemList.get(i);

        feedListRowHolder.title.setText(Html.fromHtml(feedItem.getTitle()));
        feedListRowHolder.description.setText(feedItem.getDescription());
        feedListRowHolder.url.setText(feedItem.getUrl());
    }

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

}

Answer 1

当然你可以像this那样组合使用Recycler view和EndlessScrool。 ..

这是一个例子

private boolean loading = true;
int pastVisiblesItems, visibleItemCount, totalItemCount;

mRecyclerView.setOnScrollListener(new RecyclerView.OnScrollListener() {
    @Override
    public void onScrolled(RecyclerView recyclerView, int dx, int dy) {

            visibleItemCount = mLayoutManager.getChildCount();
            totalItemCount = mLayoutManager.getItemCount();
            pastVisiblesItems = mLayoutManager.findFirstVisibleItemPosition();

            if (loading) {
                if ( (visibleItemCount + pastVisiblesItems) >= totalItemCount) {
                    loading = false;
                    Log.v("...", "Last Item Wow !");
                }
            }
     }
});

不要忘记添加

LinearLayoutManager mLayoutManager;
mLayoutManager = new LinearLayoutManager(this);
mRecyclerView.setLayoutManager(mLayoutManager);

这是一个 Github 示例:EndlessRecyclerOnScrollListener