ViewPager OnPageChangeListener Databinding

ids.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <item name="currentItemSelectedListener" type="id" />
</resources>

ViewPagerBindingAdapter.java

import android.databinding.BindingAdapter;
import android.databinding.InverseBindingAdapter;
import android.databinding.InverseBindingListener;
import android.databinding.InverseBindingMethod;
import android.databinding.InverseBindingMethods;
import android.databinding.adapters.ListenerUtil;
import android.support.v4.view.ViewPager;

import com.zdominguez.sdksandbox.R;

@InverseBindingMethods({
        @InverseBindingMethod(type = ViewPager.class,
                attribute = "currentItem",
                event = "currentItemAttrChanged",
                method = "getCurrentItem")
})
public class ViewPagerBindingAdapter {
    @InverseBindingAdapter(attribute = "currentItem", event = "currentItemAttrChanged")
    public static int getCurrentItem(ViewPager view) {
        return view.getCurrentItem();
    }

    @BindingAdapter(value = {"onPageScrolled", "onPageSelected",
            "onPageScrollStateChanged", "currentItemAttrChanged"},
            requireAll = false)
    public static void updateCurrentItem(ViewPager view, final OnPageScrolledListener onPageScrolledListener,
                                         final OnPageSelectedListener onPageSelectedListener,
                                         final OnPageScrollStateChangedListener onPageScrollStateChangedListener,
                                         final InverseBindingListener currentItemAttrChangedListener) {
        ViewPager.OnPageChangeListener onPageChangeListener;
        if (onPageScrolledListener == null && onPageSelectedListener == null && onPageScrollStateChangedListener == null
                && currentItemAttrChangedListener == null) {
            onPageChangeListener = null;
        } else {
            onPageChangeListener = new ViewPager.OnPageChangeListener() {
                @Override
                public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
                    if (onPageScrolledListener != null) {
                        onPageScrolledListener.onPageScrolled(position, positionOffset, positionOffsetPixels);
                    }
                }

                @Override
                public void onPageSelected(int position) {
                    if (onPageSelectedListener != null) {
                        onPageSelectedListener.onPageSelected(position);
                    }

                    if (currentItemAttrChangedListener != null) {
                        currentItemAttrChangedListener.onChange();
                    }
                }

                @Override
                public void onPageScrollStateChanged(int state) {
                    if (onPageScrollStateChangedListener != null) {
                        onPageScrollStateChangedListener.onPageScrollStateChanged(state);
                    }
                }
            };
        }

        final ViewPager.OnPageChangeListener oldValue = ListenerUtil.trackListener(view,
                onPageChangeListener, R.id.currentItemSelectedListener);
        if (oldValue != null) {
            view.removeOnPageChangeListener(oldValue);
        }
        if (onPageChangeListener != null) {
            view.addOnPageChangeListener(onPageChangeListener);
        }
    }

    public interface OnPageScrolledListener {
        void onPageScrolled(int position, float positionOffset, int positionOffsetPixels);
    }

    public interface OnPageSelectedListener {
        void onPageSelected(int position);
    }

    public interface OnPageScrollStateChangedListener {
        void onPageScrollStateChanged(int state);
    }
}