@Override public void onScroll(int l, int t, int oldl, int oldt) { int height = mHeader.getMeasuredHeight() - mToolbar.getMeasuredHeight(); Drawable drawable = mToolbarContainer.getBackground(); int alpha = 255 * (Math.min(Math.max(t, 0), height)) / height; drawable.setAlpha(alpha); if (alpha >= 255) { ViewCompat.setElevation(mToolbarContainer, mElevation); ViewCompat.setElevation(mHeader, 0); } else { ViewCompat.setElevation(mToolbarContainer, 0); ViewCompat.setElevation(mHeader, mElevation); } }