Yahoo News Digest ViewPager animation

MainActivity.java

import android.support.v4.view.ViewPager;
public class MainActivity extends AppCompatActivity {

    TextView tv;
    ViewPager pager;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tv = (TextView) findViewById(R.id.tv);
        pager = (ViewPager) findViewById(R.id.pager);
        pager.setAdapter(new ParallaxPagerAdapter(getApplicationContext()));
        pager.setPageMargin(20);
        pager.setPageMarginDrawable(R.color.black);
//       using tag find view
//        pager.setPageTransformer(true, new ParallaxViewTransformer(ParallaxViewTransformer.IMAGE_TAG));
//      using id find view
        pager.setPageTransformer(true, new ParallaxViewTransformer(R.id.imageview));
    }
}

ParallaxPagerAdapter.java

public class ParallaxPagerAdapter extends PagerAdapter {

    Context context;
    
   static  int[] imgRes = {R.mipmap.m1, R.mipmap.m2, R.mipmap.m3, R.mipmap.m4};

    public ParallaxPagerAdapter(Context context) {
        this.context = context;
    }

    @Override
    public void destroyItem(ViewGroup container, int position, Object object) {
        container.removeView((View) object);
    }

    @Override
    public int getCount() {
        return imgRes.length;
    }

    @Override
    public boolean isViewFromObject(View view, Object object) {
        return view ==object;
    }

    @Override
    public Object instantiateItem(ViewGroup container, int position) {

        LayoutInflater inflater = LayoutInflater.from(context);
        View views = inflater.inflate(R.layout.pager_item, container,false);

        ImageView image = (ImageView) views.findViewById(R.id.imageview);
        image.setImageResource(imgRes[position]);

//     if using tag find view
        image.setTag(ParallaxViewTransformer.IMAGE_TAG);

        container.addView(views);
        
        return views;
    }
}

ParallaxViewTransformer.java

import android.support.v4.view.ViewPager;
import android.text.TextUtils;
import android.view.View;

import com.nineoldandroids.animation.ObjectAnimator;

/**
 * Created by shau-lok on 3/23/16.
 */
public class ParallaxViewTransformer implements ViewPager.PageTransformer {


    int mImageId = -1;

    public static final String IMAGE_TAG = "parallaxViewTag";
    String imgTag = null;

    @Override
    public void transformPage(View page, float position) {

        int pageWidth = page.getWidth();

        if (mImageId > 0) {
            if (page.findViewById(mImageId) != null) {
                page = page.findViewById(mImageId);
            }

            if (position <= 0) { //[-1,0]
                if (page.getId() == mImageId) {
                    page.setTranslationX(pageWidth * -position / 1.4f);
                } else {
                    page.setTranslationX(0);
                }
            } else {//(0,1]
                page.setTranslationX(pageWidth * -position / 1.4f);
            }
        }

        if (!TextUtils.isEmpty(imgTag)) {
            if (page.findViewWithTag(imgTag) != null) {
                page = page.findViewWithTag(imgTag);
            }
            if (position <= 0) {
                if (page.getTag() == imgTag) {
//                    page.setTranslationX(pageWidth * -position / 1.4f);
                    ObjectAnimator.ofFloat(page,"translationX",pageWidth * -position / 1.4f).start();
                } else {
//                    page.setTranslationX(0);
                    ObjectAnimator.ofFloat(page,"translationX",0).start();
                }
            } else {
//                page.setTranslationX(pageWidth * -position / 1.4f);
                ObjectAnimator.ofFloat(page,"translationX",pageWidth * -position / 1.4f).start();
            }
        }



    }


    public ParallaxViewTransformer(int mImageId) {
        this.mImageId = mImageId;
    }

    public ParallaxViewTransformer(String imgTag) {
        this.imgTag = imgTag;
    }


}