在Android上滚动时如何在RecyclerView中加载更多数据 [英] How to load more data in RecyclerView when Scrolling on Android

问题描述

我想为一个网站开发android应用程序.我从json中读取网站帖子，并在RecyclerView中每10个帖子中显示一次，当用户在RecyclerView上滚动时，显示更多10个帖子并结束！ 我是业余爱好者，我在下面编写代码，但我不知道，在滚动并转到下一页时要读取更多数据！ (我想在任何页面上显示任何10条帖子.)
Json链接: JSON链接

I want develop android application for one website. I read website posts from json and show its in RecyclerView every 10 posts and when user scrolling on RecyclerView show more 10 post and go to end!
I am amateur and i write below codes, but I don't know to to read more data when scrolling and go to next page! (I want show any 10 posts in any pages).
Json link : JSON LINK

AsyncTask代码:

public class MainDataInfo {
    private Context mContext;
    private String ServerAddress = ServerIP.getIP();

    public void getMainDataInfo(Context context) {
        mContext = context;
        new getInfo().execute(ServerAddress + "page=1");
    }

    private class getInfo extends AsyncTask<String, Void, String> {
        EventBus bus = EventBus.getDefault();
        private String ou_response;
        private List<MainDataModel> infoModels;

        @Override
        protected void onPreExecute() {
            CustomProcessDialog.createAndShow(mContext);
            infoModels = new ArrayList<>();
        }

        @Override
        protected String doInBackground(String... params) {
            OkHttpClient client = new OkHttpClient();

            Request request = new Request.Builder()
                    .url(ServerAddress + "page=1")
                    .cacheControl(CacheControl.FORCE_NETWORK)
                    .build();

            Response response;
            try {
                response = client.newCall(request).execute();
                ou_response = response.body().string();
                response.body().close();
                if (ou_response != null) {
                    try {
                        JSONObject postObj = new JSONObject(ou_response);
                        JSONArray postsArray = postObj.optJSONArray("posts");
                        infoModels = new ArrayList<>();

                        for (int i = 0; i <= infoModels.size(); i++) {
                            JSONObject postObject = (JSONObject) postsArray.get(i);
                            JSONObject images=postObject.optJSONObject("thumbnail_images");
                            JSONObject imagesPair=images.optJSONObject("medium");

                            int id = postObject.getInt("id");
                            String title = postObject.getString("title");
                            String content = postObject.getString("content");
                            String thumbnail = imagesPair.getString("url");
                            Log.d("Data", "Post id: " + id);
                            Log.d("Data", "Post title: " + title);
                            Log.d("Data", "Post title: " + thumbnail);

                            //Use the title and id as per your requirement
                            infoModels.add(new MainDataModel(id, title, content, thumbnail));
                        }
                    } catch (JSONException e) {
                        e.printStackTrace();
                    }
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
            return ou_response;
        }

        @Override
        protected void onPostExecute(String result) {
            CustomProcessDialog.dissmis();
            if (result != null) {
                bus.post(infoModels);
            }
        }
    }
}

我使用此代码显示所有页面帖子: ServerAddress + "page=1"

I use this code for show any pages posts : ServerAddress + "page=1"

适配器代码:

public class MainAdapter2 extends RecyclerView.Adapter {

    private List<MainDataModel> mDateSet;
    private Context mContext;

    private final int VIEW_ITEM = 1;
    private final int VIEW_PROG = 0;

    // The minimum amount of items to have below your current scroll position
    // before loading more.
    private int visibleThreshold = 5;
    private int lastVisibleItem, totalItemCount;
    private boolean loading;
    private OnLoadMoreListener onLoadMoreListener;

    public MainAdapter2(Context context, RecyclerView recyclerView, List<MainDataModel> dataSet) {
        this.mContext = context;
        this.mDateSet = dataSet;

        if (recyclerView.getLayoutManager() instanceof LinearLayoutManager) {

            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 (!loading
                                    && totalItemCount <= (lastVisibleItem + visibleThreshold)) {
                                // End has been reached
                                // Do something
                                if (onLoadMoreListener != null) {
                                    onLoadMoreListener.onLoadMore();
                                }
                                loading = true;
                            }
                        }
                    });
        }
    }

    @Override
    public int getItemViewType(int position) {
        return mDateSet.get(position) != null ? VIEW_ITEM : VIEW_PROG;
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

        RecyclerView.ViewHolder vh;
        if (viewType == VIEW_ITEM) {
            View v = LayoutInflater.from(parent.getContext()).inflate(
                    R.layout.post_card_layout, parent, false);

            vh = new DataViewHolder(v);
        } else {
            View v = LayoutInflater.from(parent.getContext()).inflate(
                    R.layout.progressbar_item, parent, false);

            vh = new ProgressViewHolder(v);
        }
        return vh;
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {

        if (holder instanceof DataViewHolder) {
            ((DataViewHolder) holder).main_post_title.setText(mDateSet.get(position).getTitle());
            Glide.with(mContext)
                    .load(mDateSet.get(position).getThumbnail())
                    .placeholder(R.drawable.post_image)
                    .crossFade()
                    .into(((DataViewHolder) holder).main_post_image);
            ((DataViewHolder) holder).main_post_content.setText(Html.fromHtml(mDateSet.get(position).getContent()));

        } else {
            ((ProgressViewHolder) holder).progressBar.setIndeterminate(true);
        }
    }

    public void setLoaded() {
        loading = false;
    }

    @Override
    public int getItemCount() {
        return mDateSet.size();
    }

    public void setOnLoadMoreListener(OnLoadMoreListener onLoadMoreListener) {
        this.onLoadMoreListener = onLoadMoreListener;
    }

    public void remove(int position) {
        mDateSet.remove(position);
        notifyItemRemoved(position);
    }

    public void clear() {
        mDateSet.clear();
        notifyDataSetChanged();
    }


    public void add(List<MainDataModel> models) {
        mDateSet.addAll(models);
        notifyDataSetChanged();
    }

    public void update(List<MainDataModel> models) {
        mDateSet.clear();
        mDateSet.addAll(models);
        notifyDataSetChanged();
    }

    public class DataViewHolder extends RecyclerView.ViewHolder {

        private TextView main_post_title, main_post_content;
        private ImageView main_post_image;

        public DataViewHolder(View itemView) {
            super(itemView);

            main_post_title = (TextView) itemView.findViewById(R.id.post_content_title);
            main_post_image = (ImageView) itemView.findViewById(R.id.post_picture_image);
            main_post_content = (TextView) itemView.findViewById(R.id.post_content_text);
        }
    }

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

        public ProgressViewHolder(View v) {
            super(v);
            progressBar = (ProgressBar) v.findViewById(R.id.progressBar1);
        }
    }
}

MainActivity代码:

public class Main_page extends AppCompatActivity {

    private static final long RIPPLE_DURATION = 250;
    private Toolbar toolbar;
    private RelativeLayout root;
    private ImageView menu_image;
    private RecyclerView main_recyclerView;
    private MainAdapter2 mAdaper;
    private List<MainDataModel> dataModels = new ArrayList<MainDataModel>();
    private List<MainDataModel> dataModelsArray;
    private Context context;
    protected Handler handler;
    private RelativeLayout loadLayout;
    private LinearLayoutManager mLayoutManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main_page);
        if (!EventBus.getDefault().isRegistered(this)) {
            EventBus.getDefault().register(this);
        }
        handler = new Handler();
        context = getApplicationContext();
        loadLayout = (RelativeLayout) findViewById(R.id.main_empty_layout);
        toolbar = (Toolbar) findViewById(R.id.main_toolbar);
        if (toolbar != null) {
            setSupportActionBar(toolbar);
            getSupportActionBar().setTitle(null);
        }
        LoadData();
        mLayoutManager = new LinearLayoutManager(this);
        // Menu
        root = (RelativeLayout) findViewById(R.id.main_root);
        View guillotineMenu = LayoutInflater.from(this).inflate(R.layout.menu_layout, null);
        root.addView(guillotineMenu);
        menu_image = (ImageView) toolbar.findViewById(R.id.toolbar_logo);
        new GuillotineAnimation.GuillotineBuilder(guillotineMenu, guillotineMenu.findViewById(R.id.menu_layout_image), menu_image)
                .setStartDelay(RIPPLE_DURATION)
                .setActionBarViewForAnimation(toolbar)
                .setClosedOnStart(true)
                .build();
        // RecyclerView and setData
        main_recyclerView = (RecyclerView) findViewById(R.id.main_recycler);
        main_recyclerView.setHasFixedSize(true);
        main_recyclerView.setLayoutManager(mLayoutManager);

        mAdaper = new MainAdapter2(this, main_recyclerView, dataModels);
        main_recyclerView.setAdapter(mAdaper);

        mAdaper.setOnLoadMoreListener(new OnLoadMoreListener() {
            @Override
            public void onLoadMore() {

            }
        });


    }


    @Subscribe
    public void onEvent(List<MainDataModel> mainInfoModels) {
        mAdaper.add(mainInfoModels);

        if (dataModels.isEmpty()) {
            main_recyclerView.setVisibility(View.GONE);
            loadLayout.setVisibility(View.VISIBLE);

        } else {
            main_recyclerView.setVisibility(View.VISIBLE);
            loadLayout.setVisibility(View.GONE);
        }
    }

    private void LoadData() {
        final MainDataInfo dataInfo = new MainDataInfo();
        dataInfo.getMainDataInfo(this);
    }

为了加载更多数据，我使用 Interface 类:OnLoadMoreListener

for load more data i use Interface class : OnLoadMoreListener

注意::我知道此方法的名称是无止境的！但是我是业余爱好者，我不知道在mAdapter.setOnMoreListener中编写代码来加载更多数据！请不要给我负面点，帮助我，我真的需要您的帮助！谢谢所有< 3

Attention : I know the name of this method is endless! but i am amateur and i don't know to write code in mAdapter.setOnMoreListener to load more data! Please don't give me negative points, help me and i really need you helps! thanks all <3

推荐答案

将onLoadMoreListener添加到您的适配器中，

Add onLoadMoreListener to your adapter,

  adapter.setOnLoadMoreListener(onLoadMoreListener);

然后在onLoadMore()中实现以下代码:

Then Implement below code in onLoadMore():

OnLoadMoreListener onLoadMoreListener = new OnLoadMoreListener() {
    @Override
    public void onLoadMore() {
        //Here adding null object to last position,check the condition in getItemViewType() method,if object is null then display progress
        dataModels.add(null);
        adapter.notifyItemInserted(dataModels.size() - 1);

        new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {
                dataModels.remove(dataModels.size() - 1);
                adapter.notifyItemRemoved(dataModels.size());

                // Call you API, then update the result into dataModels, then call adapter.notifyDataSetChanged(). 
                //Update the new data into list object
                loadData();
                adapter.notifyDataSetChanged();
                loading = false;
            }
        }, 1000);
    }
};

您的方法:

      private void LoadData() {
             MainDataInfo dataInfo = new MainDataInfo();
            // here getMainDataInfo() should return the server response
             dataInfo.getMainDataInfo(this);
      }

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