android只title背景色隨着滾動漸變顏色

	scrollView.setScrollViewListener(new ScrollViewListener() {
			@Override
			public void onScrollChanged(MallHomePageScrollView scrollView, int x, int y, int oldx, int oldy)
				{
					float scale = (float) y / (float) backgroundHeight;
					newAlpha = scale * 255.000f;
					if (newAlpha > 255) {
						newAlpha = 255.00f;
					}
					titleRl.getBackground().setAlpha((int) newAlpha);
				}
		});

backgroundHeight = Tools.dip2px(UserDetailAct.this, 251);