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

public class ScrollActivity extends BaseActivity {

    /* view binding */
    @BindView(R.id.scrollView)ScrollView scrollView;
    @BindView(R.id.parallax_image)ImageView parallaxImage;
    @BindView(R.id.tv_perhour)TextView textView;
    @BindView(R.id.tv_heading)TextView heading;
    /* color binding */
    @BindColor(R.color.white)int whiteColor;
    @BindColor(android.R.color.transparent)int transparentColor;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        /* intially hide the view */
        heading.setAlpha(0f);
        /* set the scroll change listener on scrollview */
        scrollView.getViewTreeObserver().addOnScrollChangedListener(new ViewTreeObserver.OnScrollChangedListener() {
            @Override
            public void onScrollChanged() {
                /* get the maximum height which we have scroll before performing any action */
                int maxDistance = parallaxImage.getHeight();
                /* how much we have scrolled */
                int movement = scrollView.getScrollY();
                /*finally calculate the alpha factor and set on the view */
                float alphaFactor = ((movement * 1.0f) / (maxDistance - heading.getHeight()));
                if (movement >= 0 && movement <= maxDistance) {
                    /*for image parallax with scroll */
                    parallaxImage.setTranslationY(-movement/2);
                    /* set visibility */
                    heading.setAlpha(alphaFactor);
                }
            }
        });
    }

    /* can be replaced with setContentView() in onCreate() */
    /* kept for brevity */
    @Override
    protected int getActivityLayout() {
        return R.layout.ac_parallax;
    }
}