UkolListFragment.java

package cz.grejtCZ.ukolnicek.android.headeredList;

import android.arch.lifecycle.LifecycleOwner;
import android.arch.lifecycle.LiveData;
import android.arch.lifecycle.Observer;
import android.arch.lifecycle.ViewModel;
import android.arch.lifecycle.ViewModelProviders;
import android.arch.paging.LivePagedListBuilder;
import android.arch.paging.PagedList;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.design.widget.FloatingActionButton;
import android.support.v4.app.Fragment;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import cz.grejtCZ.ukolnicek.android.R;
import cz.grejtCZ.ukolnicek.android.activity.MainActivity;
import cz.grejtCZ.ukolnicek.android.sql.DMO;
import cz.grejtCZ.ukolnicek.android.sql.MojeDAO;

/**
 */
public class UkolListFragment extends Fragment {
    private static final String SIS_LIST_ID = "listID";
    private byte pripravenost = 0; //readyness; indikuje jak moc je fragment pripraven 0 - vůbec; 1 - vytvořeny View; 2 - data připravena; 3 - View naplněny

    private long listID;

    RecyclerView recyclerView;
    FloatingActionButton addButton;

    UkolListAdapter adapter;
    UkolViewModel model;

    private MainActivity.ClickCallback clickCallBack;

    public UkolListFragment() {
        // Required empty public constructor
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (savedInstanceState != null && savedInstanceState.containsKey(SIS_LIST_ID)) {
            listID = savedInstanceState.getLong(SIS_LIST_ID);
            if (pripravenost == 1) {
                pripravenost = 3;
                postInit();
            } else {
                pripravenost = 2;
            }
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_ukol_list, container, false);

        recyclerView = view.findViewById(R.id.recyclerView);
        addButton = view.findViewById(R.id.addButton);

        if (pripravenost == 2) {
            pripravenost = 3;
            postInit();
        } else {
            pripravenost = 1;
        }
        return view;
    }

    public void init(long listID, MainActivity.ClickCallback clickCallBack) {
        this.clickCallBack = clickCallBack;
        this.listID = listID;
        if (pripravenost == 1 || pripravenost == 3) {
            pripravenost = 3;
            postInit();
        } else {
            pripravenost = 2;
        }
    }

    /**
     * nacte data a naplni Viewy
     * loads data and fill Views
     */
    private void postInit() {
        adapter = new UkolListAdapter(getContext(), clickCallBack);
        if (model != null){ //odstaneni starych observeru
            model.list.removeObservers(this);
        }
        model = ViewModelProviders.of(this).get(UkolViewModel.class);
        model.init(DMO.getDao(), listID, this);
        recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
        recyclerView.setAdapter(adapter);
        model.list.observe(this, new Observer<PagedList<UkolOrHeader>>() {
            @Override
            public void onChanged(@Nullable PagedList<UkolOrHeader> ukolOrHeaders) {
                adapter.submitList(ukolOrHeaders);
            }
        });

        addButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                clickCallBack.add();
            }
        });
    }

    @Override
    public void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        //outState.putLong(SIS_LIST_ID, listID);
    }

    public static class UkolViewModel extends ViewModel {
        public LiveData<PagedList<UkolOrHeader>> list;
        public LiveData<Integer> headers;

        public void init(MojeDAO dao, Long listID, LifecycleOwner owner) {
            if (headers != null){ //odstraneni predchozich observeru
                headers.removeObservers(owner);
            }
            final MyDatasource.Factory factory = new MyDatasource.Factory(dao.loadUkolsFactory(listID), listID);
            list = new LivePagedListBuilder<>(factory, 20).build();
        }

        public UkolViewModel() {
        }
    }
}