HideShowRecyclerParallaxActivity.java

/**
 * Created by Saurabh(aqua) in 2017.
 */

public class HideShowRecyclerParallaxActivity extends BaseActivity {

    /* view binding */
    @BindView(R.id.recycler_view)RecyclerView recyclerView;
    @BindView(R.id.parallax_image)ImageView parallaxImage;
    @BindView(R.id.tv_heading)AppTextView heading;
   
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        /* hide the heading initially */
        heading.setAlpha(0f);
        ParallaxAdapter adapter = new ParallaxAdapter();
        recyclerView.setAdapter(adapter);
        recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
            @Override
            public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
                super.onScrolled(recyclerView, dx, dy);
                /* calcaulate the range we need to cover */
                int maxDistance = recyclerView.getPaddingTop();
                /* calculate the amount of scroll */
                int movement = maxDistance - recyclerView.getChildAt(0).getTop();
                /* calculate the alpha value for heading based on scrolling */
                float alphaFactor = ((movement * 1.0f) / (maxDistance - heading.getHeight()));
                if (movement >= 0 && movement <= maxDistance) {
                    /* parallaxing the image */
                    parallaxImage.setTranslationY(-movement/2);
                    /* hide/show the heading based on alpha */
                    heading.setAlpha(alphaFactor);
                } else {
                    parallaxImage.setTranslationY(-maxDistance);
                }
            }
        });
    }

    @Override
    protected int getActivityLayout() {
        return R.layout.ac_parallax;
    }
}