[안드로이드 Paging] 시작하기

설정

ㆍ종속성 설정

dependencies {
    implementation "androidx.paging:paging-runtime:2.1.0" // For Kotlin use paging-runtime-ktx
}

ConcertViewModel.java

ㆍViewModel 생성

public class ConcertViewModel extends ViewModel {
    private ConcertDao concertDao;
    public final LiveData<PagedList<Concert>> concertList;
 
    public ConcertViewModel(ConcertDao concertDao) {
        this.concertDao = concertDao;
        concertList = new LivePagedListBuilder<>(
            concertDao.concertsByDate(), /* page size */ 50).build();
    }
}

ConcertDao.java

ㆍDAO 생성

@Dao
public interface ConcertDao {
    // The Integer type parameter tells Room to use a PositionalDataSource
    // object, with position-based loading under the hood.
    @Query("SELECT * FROM concerts ORDER BY date DESC")
    DataSource.Factory<Integer, Concert> concertsByDate();
}

ConcertAdapter.java

ㆍPagedListAdapter 생성

public class ConcertAdapter
        extends PagedListAdapter<Concert, ConcertViewHolder> {
    protected ConcertAdapter() {
        super(DIFF_CALLBACK);
    }
 
    @Override
    public void onBindViewHolder(@NonNull ConcertViewHolder holder,
            int position) {
        Concert concert = getItem(position);
        if (concert != null) {
            holder.bindTo(concert);
        } else {
            // Null defines a placeholder item - PagedListAdapter automatically
            // invalidates this row when the actual object is loaded from the
            // database.
            holder.clear();
        }
    }
 
    private static DiffUtil.ItemCallback<Concert> DIFF_CALLBACK =
            new DiffUtil.ItemCallback<Concert>() {
        // Concert details may have changed if reloaded from the database,
        // but ID is fixed.
        @Override
        public boolean areItemsTheSame(Concert oldConcert, Concert newConcert) {
            return oldConcert.getId() == newConcert.getId();
        }
 
        @Override
        public boolean areContentsTheSame(Concert oldConcert,
                Concert newConcert) {
            return oldConcert.equals(newConcert);
        }
    };
}

ConcertActivity.java

ㆍViewModel과 Adapter 연결

public class ConcertActivity extends AppCompatActivity {
    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        ConcertViewModel viewModel =
                ViewModelProviders.of(this).get(ConcertViewModel.class);
        RecyclerView recyclerView = findViewById(R.id.concert_list);
        ConcertAdapter adapter = new ConcertAdapter();
        viewModel.concertList.observe(this, adapter::submitList);
        recyclerView.setAdapter(adapter);
    }
}

다른 예제 with RxJava2

public class ConcertViewModel extends ViewModel {
    private ConcertDao concertDao;
    public final Observable<PagedList<Concert>> concertList;
 
    public ConcertViewModel(ConcertDao concertDao) {
        this.concertDao = concertDao;
 
        concertList = new RxPagedListBuilder<>(
                concertDao.concertsByDate(), /* page size */ 50)
                        .buildObservable();
    }
}

public class ConcertActivity extends AppCompatActivity {
    private ConcertAdapter adapter = new ConcertAdapter();
    private ConcertViewModel viewModel;
 
    private CompositeDisposable disposable = new CompositeDisposable();
 
    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        RecyclerView recyclerView = findViewById(R.id.concert_list);
 
        viewModel = ViewModelProviders.of(this).get(ConcertViewModel.class);
        recyclerView.setAdapter(adapter);
    }
 
    @Override
    protected void onStart() {
        super.onStart();
        disposable.add(viewModel.concertList
                .subscribe(adapter.submitList(flowableList)
        ));
    }
 
    @Override
    protected void onStop() {
        super.onStop();
        disposable.clear();
    }
}

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출처

https://developer.android.com/topic/libraries/architecture/paging