Android ScrollView -- fade a view in or out depending on the vertical scroll postion

gistfile1.txt

mScrollView.getViewTreeObserver().addOnScrollChangedListener(new ViewTreeObserver.OnScrollChangedListener() {
				@Override
				public void onScrollChanged() {
				     // the scrollposition that the fade will start
				     int mScrollThreshold = 100;
				     // how fast the view will fade with the scroll -- use multiples of 10
					int mScrollVariance = 40;
					int scrollY = mScrollView.getScrollY();
					// if the difference between the scrollthreshold is +/-mScrollVariance, show the view accordingly
					float newAlpha = 0;
					float scrollDisparity = scrollY - mScrollThreshold + (mToolbarSeriesTitle.getHeight()/2);
					// scroll is up past the variance, so start to show it
					if(scrollDisparity > 0 && scrollDisparity < mScrollVariance) {
						newAlpha = scrollDisparity / mScrollVariance;
						mToolbarSeriesTitle.setAlpha(newAlpha);
					// scroll is below the variance so start to hide it
					}else if (scrollDisparity >= -mScrollVariance && scrollDisparity < 0) {
						newAlpha = scrollDisparity / mScrollVariance;
						mToolbarSeriesTitle.setAlpha(newAlpha);
					// just in case the user swipes too fast, these are the fallbacks
					}else if(scrollDisparity > mScrollVariance){
						mToolbarSeriesTitle.setAlpha(1);
					}else if(scrollDisparity < -mScrollVariance){
						mToolbarSeriesTitle.setAlpha(0);
					}
				}    
		     });