如何在android中实现加载更多的recyclerview

Question

我想在Recyclerview中实现更多的加载.这是代码.代码来自github.https://gist.github.com/ssinss/e06f12ef66c51252563e

MainActivity代码:

package com.example.tatson.bila;
import android.app.ProgressDialog;
import android.os.AsyncTask;

import android.support.v4.widget.SwipeRefreshLayout;
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 android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.JsonArrayRequest;
import com.android.volley.toolbox.Volley;
import com.example.tatson.bila.CardAdapter;
import com.example.tatson.bila.Config;
import com.example.tatson.bila.SuperHeroes;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import org.w3c.dom.Text;

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


public class MainActivity extends AppCompatActivity  implements SwipeRefreshLayout.OnRefreshListener{

    SwipeRefreshLayout swipeLayout;

    LinearLayoutManager mLayoutManager;

    // initially offset will be 0, later will be updated while parsing the json
    private int offSet = 0;

    private int previousTotal = 0;


    int pastVisiblesItems, visibleItemCount, totalItemCount;
    private boolean loading = true; // True if we are still waiting for the last set of data to load.
    private int visibleThreshold = 5; // The minimum amount of items to have below your current scroll position before loading more.
    int firstVisibleItem;
    private int current_page = 1;
    //Creating a List of superheroes
    private List<SuperHeroes> listSuperHeroes;

    //Creating Views
    private RecyclerView recyclerView;
    private RecyclerView.LayoutManager layoutManager;
    private RecyclerView.Adapter adapter;
    public String Img;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        //Initializing Views
        recyclerView = (RecyclerView) findViewById(R.id.recyclerView);
        recyclerView.setHasFixedSize(true);
        layoutManager = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(layoutManager);

        LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);

        //Initializing our superheroes list
        listSuperHeroes = new ArrayList<>();


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

        swipeLayout = (SwipeRefreshLayout) findViewById(R.id.swipe_container);
        swipeLayout.setOnRefreshListener(this);
        swipeLayout.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);

        swipeLayout.post(new Runnable() {
                             @Override
                             public void run() {
                                 swipeLayout.setRefreshing(true);

                                 getData();
                             }
                         }
        );

        recyclerView.addOnScrollListener(new EndlessRecyclerOnScrollListener(linearLayoutManager) {
            @Override
            public void onLoadMore(int current_page) {

               Log.d("End","Sucess");

            }
        });

    }


    //This method will get data from the web api
    private void getData(){
        //Showing a progress dialog
        // final ProgressDialog loading = ProgressDialog.show(this,"Loading Data", "Please wait...",false,false);

// appending offset to url
        String url = Config.DATA_URL;
        String url1 = url + offSet;
        //Creating a json array request
        JsonArrayRequest jsonArrayRequest = new JsonArrayRequest(url1,
                new Response.Listener<JSONArray>() {
                    @Override
                    public void onResponse(JSONArray response) {
                        //Dismissing progress dialog
                        // loading.dismiss();

                        //calling method to parse json array
                        parseData(response);
                        adapter.notifyDataSetChanged();
                        // stopping swipe refresh
                        swipeLayout.setRefreshing(false);
                    }

                },

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

                    }
                });



        //Creating request queue
        RequestQueue requestQueue = Volley.newRequestQueue(this);

        //Adding request to the queue
        requestQueue.add(jsonArrayRequest);


    }

    //This method will parse json data
    private void parseData(JSONArray array){
        for(int i = 0; i<array.length(); i++) {
            SuperHeroes superHero = new SuperHeroes();
            CardAdapter car = new CardAdapter();
            JSONObject json = null;
            try {
                json = array.getJSONObject(i);
                superHero.setImageUrl(json.getString(Config.TAG_IMAGE_URL));
                Img =json.getString(Config.TAG_IMAGE_URL);
                superHero.setName(json.getString(Config.TAG_NAME));
                superHero.setRank(json.getInt(Config.TAG_RANK));
                // superHero.setRealName(json.getString(Config.TAG_REAL_NAME));
                //superHero.setCreatedBy(json.getString(Config.TAG_CREATED_BY));
                //superHero.setFirstAppearance(json.getString(Config.TAG_FIRST_APPEARANCE));
                int rank = json.getInt("pid");

                // updating offset value to highest value
                if (rank >= offSet)
                    offSet = rank;

                //  ArrayList<String> powers = new ArrayList<String>();

                //JSONArray jsonArray = json.getJSONArray(Config.TAG_POWERS);

               /* for(int j = 0; j<jsonArray.length(); j++){
                    powers.add(((String) jsonArray.get(j))+"\n");
                }*/
                //superHero.setPowers(powers);
                Log.d("test",Img);
                car.setImageUrl(Img);


            } catch (JSONException e) {
                e.printStackTrace();
            }
            listSuperHeroes.add(superHero);

        }

        //Finally initializing our adapter
        adapter = new CardAdapter(listSuperHeroes, this);

        //Adding adapter to recyclerview
        recyclerView.setAdapter(adapter);

    }


    @Override
    public void onRefresh() {
        listSuperHeroes.clear();

       refreshItems();
    }
    void refreshItems() {
        // Load items
        getData();

        // Load complete
        onItemsLoadComplete();
    }
    void onItemsLoadComplete() {
        // Update the adapter and notify data set changed
        adapter.notifyDataSetChanged();
        //Finally initializing our adapter
        adapter = new CardAdapter(listSuperHeroes, this);

        //Adding adapter to recyclerview
        recyclerView.setAdapter(adapter);

        // Stop refresh animation

    }
} 

EndlessRecyclerOnScrollListener类代码:

 package com.example.tatson.bila;

/**
 * Created by Tatson on 23-11-2015.
 */
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;

public abstract class EndlessRecyclerOnScrollListener extends RecyclerView.OnScrollListener {
    public static String TAG = EndlessRecyclerOnScrollListener.class.getSimpleName();

    private int previousTotal = 0; // The total number of items in the dataset after the last load
    private boolean loading = true; // True if we are still waiting for the last set of data to load.
    private int visibleThreshold = 5; // The minimum amount of items to have below your current scroll position before loading more.
    int firstVisibleItem, visibleItemCount, totalItemCount;

    private int current_page = 1;

    private LinearLayoutManager mLinearLayoutManager;

    public EndlessRecyclerOnScrollListener(LinearLayoutManager linearLayoutManager) {
        this.mLinearLayoutManager = linearLayoutManager;
    }

    @Override
    public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
        super.onScrolled(recyclerView, dx, dy);

        visibleItemCount = recyclerView.getChildCount();
        totalItemCount = mLinearLayoutManager.getItemCount();
        firstVisibleItem = mLinearLayoutManager.findFirstVisibleItemPosition();

        if (loading) {
            if (totalItemCount > previousTotal) {
                loading = false;
                previousTotal = totalItemCount;
            }
        }
        if (!loading ) {
            // End has been reached

            // Do something
            current_page++;
            Log.d("End", "Sucess");

            onLoadMore(current_page);

            loading = true;
        }
    }

    public abstract void onLoadMore(int current_page);
}

谢谢.

Answer 1

我在这里找到了一个答案,我相信,这比我在SO和其他地方看到的大多数要好得多.

这个想法很简单:在onScrolled您的RecyclerView的ScrollListener中,检查最后一个完全可见的项是否是数据集中的最后一项.

        if(llm.findLastCompletelyVisibleItemPosition() == data.length() -1){
            //bottom of list!
            loadMoreData();
        }

这种情况发生在LinearLayoutManager.调用LinearLayoutManager#findLastCompletelyVisibleItemPosition()可以将它与数据集中最后一项的位置进行比较,让您知道什么时候可以加载更多.

我没有试过这个GridLayoutManager.

UPDATE

LinearLayoutManager#findLastVisibleItemPosition()是一个更好的替代品LinearLayoutManager#findLastCompletelyVisibleItemPosition(),尤其是当您的物品长于窗户高度时.

Answer 2

检查您当前是否有要向下滚动的项目 -

if (! recyclerView.canScrollVertically(1))

如果是 - 加载更多项目，例如，使用 HTTP 客户端。

完整代码：

recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
            @Override
            public void onScrolled(@NonNull RecyclerView recyclerView, int dx, int dy) {
                super.onScrolled(recyclerView, dx, dy);
                if (! recyclerView.canScrollVertically(1)){ //1 for down
                    loadMore();
                }
            }
        });

Answer 3

在Kotlin你可以使用下面的代码片段。

    recyclerView.addOnScrollListener(object : RecyclerView.OnScrollListener() {
        override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
            super.onScrolled(recyclerView, dx, dy)
            if(!recyclerView.canScrollVertically(1)) {
                // LOAD MORE
            }
        }
    })

Answer 4

尝试这个....

  static boolean loadmore=true;
  LinearLayoutManager layoutManager = ((LinearLayoutManager)recyclerView.getLayoutManager());
   recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
        @Override
        public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
            // super.onScrolled(recyclerView, dx, dy);
            int lastVisiblePosition = layoutManager.findLastVisibleItemPosition();
            if (lastVisiblePosition == recyclerView.getChildCount()) {
                if (loadmore) {
                    loadmore = false;
                   method();
                }
            }
        }
    });


  private void method(){
      loadmore=true;
  }