Inner class used to calculate if a view is visible within it's parent.

VisibilityTracker.java

static class VisibilityChecker {
        private final Rect mClipRect = new Rect();


        boolean isVisible(@Nullable final View view, final int minPercentageViewed) {
            if (view == null || view.getVisibility() != View.VISIBLE || view.getParent() == null) {
                return false;
            }

            if (!view.getGlobalVisibleRect(mClipRect)) {
                return false;
            }

            final long visibleArea = (long) mClipRect.height() * mClipRect.width();
            final long totalViewArea = (long) view.getHeight() * view.getWidth();

            return totalViewArea > 0 && 100 * visibleArea >= minPercentageViewed * totalViewArea;

        }


    }