reactive scrollview (able to detect scroll gesture)

ReactiveScrollView.java

package evalu.com.evalu.utils.rx;

import android.content.Context;
import android.os.Build;
import android.support.annotation.RequiresApi;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.widget.ScrollView;

import io.reactivex.subjects.PublishSubject;
import io.reactivex.subjects.Subject;

/**
 * Created by Lukasz Marczak on 10.03.17.
 */

public class ReactiveScrollView extends ScrollView {

    public Subject<Boolean> scrolledUpSubject = PublishSubject.create();

    public float threshold = 20;

    public ReactiveScrollView(Context context) {
        super(context);
    }

    public ReactiveScrollView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public ReactiveScrollView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
    public ReactiveScrollView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);
    }

    private float mTouchPosition;
    private float mReleasePosition;

    @Override
    public boolean onTouchEvent(MotionEvent event) {

        if (event.getAction() == MotionEvent.ACTION_DOWN) {
            mTouchPosition = event.getY();
        }
        if (event.getAction() == MotionEvent.ACTION_UP) {
            mReleasePosition = event.getY();

            float diff = mTouchPosition - mReleasePosition;

            if (diff > threshold) {
                // user scroll down
                scrolledUpSubject.onNext(false);
            } else if (diff < -threshold) {
                scrolledUpSubject.onNext(true);
                //user scroll up
            }
        }
        return super.onTouchEvent(event);
    }
}