ListViewScrollEvent.java

import android.support.annotation.CheckResult;
import android.support.annotation.NonNull;
import android.widget.AbsListView;

import com.jakewharton.rxbinding.view.ViewEvent;

public final class ListViewScrollEvent extends ViewEvent<AbsListView> {

    @CheckResult
    @NonNull
    public static ListViewScrollEvent create(AbsListView listView, int scrollState,
            int firstVisibleItem, int visibleItemCount, int totalItemCount) {
        return new ListViewScrollEvent(listView, scrollState, firstVisibleItem, visibleItemCount,
                totalItemCount);
    }

    public final int scrollState;
    public final int firstVisibleItem;
    public final int visibleItemCount;
    public final int totalItemCount;

    private ListViewScrollEvent(@NonNull AbsListView view, int scrollState,
            int firstVisibleItem, int visibleItemCount, int totalItemCount) {
        super(view);
        this.scrollState = scrollState;
        this.firstVisibleItem = firstVisibleItem;
        this.visibleItemCount = visibleItemCount;
        this.totalItemCount = totalItemCount;
    }

    public int scrollState() {
        return scrollState;
    }

    public int firstVisibleItem() {
        return firstVisibleItem;
    }

    public int visibleItemCount() {
        return visibleItemCount;
    }

    public int totalItemCount() {
        return totalItemCount;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        ListViewScrollEvent that = (ListViewScrollEvent) o;

        if (scrollState != that.scrollState) return false;
        if (firstVisibleItem != that.firstVisibleItem) return false;
        if (visibleItemCount != that.visibleItemCount) return false;
        return totalItemCount == that.totalItemCount;

    }

    @Override
    public int hashCode() {
        int result = scrollState;
        result = 31 * result + firstVisibleItem;
        result = 31 * result + visibleItemCount;
        result = 31 * result + totalItemCount;
        return result;
    }

    @Override
    public String toString() {
        return "ListViewScrollEvent{" +
                "scrollState=" + scrollState +
                ", firstVisibleItem=" + firstVisibleItem +
                ", visibleItemCount=" + visibleItemCount +
                ", totalItemCount=" + totalItemCount +
                '}';
    }
}

ListViewScrollEventOnSubscribe.java

import android.widget.AbsListView;

import rx.Observable;
import rx.Subscriber;
import rx.android.MainThreadSubscription;

import static com.jakewharton.rxbinding.internal.Preconditions.checkUiThread;

public final class ListViewScrollEventOnSubscribe
        implements Observable.OnSubscribe<ListViewScrollEvent> {

    final AbsListView view;

    public ListViewScrollEventOnSubscribe(AbsListView view) {
        this.view = view;
    }

    @Override
    public void call(final Subscriber<? super ListViewScrollEvent> subscriber) {
        checkUiThread();

        final AbsListView.OnScrollListener listener = new AbsListView.OnScrollListener() {
            int currentScrollState = SCROLL_STATE_IDLE;

            @Override
            public void onScrollStateChanged(AbsListView view, int scrollState) {
                this.currentScrollState = scrollState;
            }

            @Override
            public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount,
                    int totalItemCount) {
                if (!subscriber.isUnsubscribed()) {
                    ListViewScrollEvent event = ListViewScrollEvent
                            .create(view, this.currentScrollState, firstVisibleItem,
                                    visibleItemCount, totalItemCount);
                    subscriber.onNext(event);
                }
            }
        };

        view.setOnScrollListener(listener);

        subscriber.add(new MainThreadSubscription() {
            @Override
            protected void onUnsubscribe() {
                view.setOnScrollListener(null);
            }
        });
    }
}

RxListView.java

import android.support.annotation.CheckResult;
import android.support.annotation.NonNull;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;

import rx.Observable;

import static com.google.common.base.Preconditions.checkNotNull;

public final class RxListView {

    /**
     * Create an observable of scroll events on {@code listView}.
     * <p>
     * <em>Warning:</em> The created observable keeps a strong reference to {@code listView}.
     * Unsubscribe to free this reference.
     * * <p>
     * <em>Warning:</em> The created observable uses {@link AbsListView#setOnScrollListener(OnScrollListener)}
     * to observe scroll changes. Only one observable can be used for a view at a time.
     * <p>
     */
    @CheckResult
    @NonNull
    public static Observable<ListViewScrollEvent> scrollEvents(@NonNull AbsListView view) {
        checkNotNull(view, "view == null");

        return Observable.create(new ListScrollEventOnSubscribe(view));
    }
}

RxListViewTest.java

import android.app.Instrumentation;
import android.support.test.InstrumentationRegistry;
import android.support.test.rule.ActivityTestRule;
import android.support.test.runner.AndroidJUnit4;
import android.widget.ListView;

import com.jakewharton.rxbinding.RecordingObserver;

import org.junit.Before;
import org.junit.Rule;
import org.junit.Test;
import org.junit.runner.RunWith;

import rx.Subscription;
import rx.android.schedulers.AndroidSchedulers;

import static com.google.common.truth.Truth.assertThat;

@RunWith(AndroidJUnit4.class)
public final class RxListViewTest {
    @Rule
    public final ActivityTestRule<RxListViewTestActivity> activityRule =
            new ActivityTestRule<>(RxListViewTestActivity.class);

    private Instrumentation instrumentation = InstrumentationRegistry.getInstrumentation();

    private RxListViewTestActivity activity;
    private ListView listView;

    @Before
    public void setUp() {
        activity = activityRule.getActivity();
        listView = activity.listView;
    }

    @Test
    public void scrollEvents() {
        RecordingObserver<ListViewScrollEvent> o = new RecordingObserver<>();
        Subscription subscription = RxListView.scrollEvents(listView) //
                .subscribeOn(AndroidSchedulers.mainThread()) //
                .subscribe(o);
        o.assertNoMoreEvents();

        instrumentation.runOnMainSync(new Runnable() {
            @Override
            public void run() {
                listView.smoothScrollToPosition(50);
            }
        });
        ListViewScrollEvent event = o.takeNext();
        assertThat(event.view()).isEqualTo(listView);
        assertThat(event.firstVisibleItem()).isEqualTo(2);
        assertThat(event.totalItemCount()).isEqualTo(100);

        subscription.unsubscribe();

        instrumentation.runOnMainSync(new Runnable() {
            @Override
            public void run() {
                listView.smoothScrollToPosition(100);
            }
        });
        o.assertNoMoreEvents();
    }
}

RxListViewTestActivity.java

import android.app.Activity;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.FrameLayout;
import android.widget.ListView;

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

public final class RxListViewTestActivity extends Activity {
    ListView listView;

    List<String> values;
    ArrayAdapter<String> adapter;

    @Override protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        values = createValues(100);
        adapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, values);

        listView = new ListView(this);
        listView.setAdapter(adapter);

        FrameLayout layout = new FrameLayout(this);
        layout.addView(listView);
        setContentView(layout);
    }

    private static List<String> createValues(int count) {
        final List<String> values = new ArrayList<String>(count);
        for (int i = 0; i < count; i++) {
            values.add(String.valueOf(i));
        }
        return values;
    }
}

prob does the same but use this import static com.jakewharton.rxbinding.internal.Preconditions.checkNotNull;