Code for paging library

gistPagingLibrary.txt

package com.sw.hc.surge.adapter.fitness


import android.arch.paging.PagedListAdapter
import android.content.Context
import android.support.v7.util.DiffUtil
import android.support.v7.widget.RecyclerView
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import com.sw.hc.surge.R
import com.sw.hc.surge.model.wellbeing.Resource
import kotlinx.android.synthetic.main.row_wellbeing_resource_item.view.*

class ResourcesAdapter(private val context: Context) : PagedListAdapter<Resource, ResourcesAdapter.ViewHolder>(DIFF_CALLBACK) {

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        val itemView = LayoutInflater.from(parent.context)
                .inflate(R.layout.row_wellbeing_resource_item, parent, false)

        return ViewHolder(itemView)
    }

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {

        holder.bind(position)
    }

    inner class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {

        fun bind(position: Int) {

            val resource = getItem(position)

            with(itemView) {

                tv_type.text = resource?.title
            }
        }
    }

    companion object {

        private val DIFF_CALLBACK = object : DiffUtil.ItemCallback<Resource>() {
            override fun areItemsTheSame(oldItem: Resource, newItem: Resource): Boolean {
                return oldItem.postId == newItem.postId // todo: make three =
            }

            override fun areContentsTheSame(oldItem: Resource, newItem: Resource): Boolean {
                return oldItem == newItem
            }
        }
    }
}






public class ItemViewModel extends ViewModel {

    public LiveData<PagedList<Resource>> itemPagedList;
    public LiveData<PageKeyedDataSource<Integer, Resource>> liveDataSource;

    public ItemViewModel() {

        ItemDataSourceFactory itemDataSourceFactory = new ItemDataSourceFactory();
        liveDataSource = itemDataSourceFactory.getItemLiveDataSource();

        PagedList.Config config =
                (new PagedList.Config.Builder())
                        .setEnablePlaceholders(false)
                        .setPageSize(ItemDataSource.Companion.getPAGE_SIZE())
                        .build();

        itemPagedList = (new LivePagedListBuilder(itemDataSourceFactory, config)).build();

    }
}






public class ItemDataSourceFactory extends DataSource.Factory {

    private MutableLiveData<PageKeyedDataSource<Integer, Resource>> itemLiveDataSource = new MutableLiveData<>();


    @Override
    public DataSource create() {
        ItemDataSource itemDataSource = new ItemDataSource();
        itemLiveDataSource.postValue(itemDataSource);
        return itemDataSource;
    }

    public MutableLiveData<PageKeyedDataSource<Integer, Resource>> getItemLiveDataSource() {
        return itemLiveDataSource;
    }
}





public class GetAllResourceListAPI {

    private static String LOG_TAG =  "GetAllResourceListAPI";

    public interface ThisCallback {

        void onSuccess(GetResourceList getResourceList);

        void onFailure(String failureMessage);

        void onError(String errorMessage);
    }


    /* POST */
    public static void postData(JsonObject jo, final ThisCallback callback) {
        Call<JsonObject> call = Service.getService().get_all_resource_list(jo);
        call.enqueue(new Callback<JsonObject>() {

            @Override
            public void onResponse(Call<JsonObject> call, Response<JsonObject> response) {

                try {
                    if (response.body().get("success").getAsBoolean()) {
                        Log.e(LOG_TAG, "success");

                        Gson gson = new GsonBuilder().setPrettyPrinting().create();
                        GetResourceList getResourceList = gson.fromJson(response.body(), GetResourceList.class);

                        callback.onSuccess(getResourceList);

                    } else {
                        Log.e(LOG_TAG, "else");

                        String error = response.body().get("err").getAsString();

                        callback.onError(error);
                    }

                } catch (Exception e) {
                    Log.e(LOG_TAG, "exception" + e.getLocalizedMessage());
                    
                    callback.onFailure(e.getMessage());
                }
            }

            @Override
            public void onFailure(Call<JsonObject> call, Throwable t) {
                Log.e(LOG_TAG, "onFailure" + t.getMessage());

                callback.onFailure(t.getMessage());
            }
        });
    }
}