android Recyclerview仿京东，滚动屏幕标题栏渐变（启动页面动画）

首先，本文代码部分参考了conglida博主写的自定义scrollview 实现标题栏渐变：

http://download.csdn.net/download/conglida/9183723

此资源只使用自定义scrollview 实现标题栏渐变和上拉下拉刷新。如果需要listview，等其他控件，需实现onScrollListener，在onscroll中嵌入渐变代码。

再次感谢conglida博主的无私奉献！

由于Recyclerview已经推出很长时间了，不得不说这个控件确实好，可以替代scrollview、listview、gridview，功能很强大，目前我已经用这个新控件实现了标题栏渐变的效果。

本代码使用了三方开源组件：

HeaderAndFooterRecyclerView

HeaderAndFooterRecyclerView是支持addHeaderView、 addFooterView、分页加载的RecyclerView解决方案，滑动底部自动加载更多。

项目地址：https://github.com/cundong/HeaderAndFooterRecyclerView

开始正题。

布局文件：

部分代码：

CommonHeader headerView;
    private void initView(View view) {

        mSwipeRefreshLayout = (SwipeRefreshLayout)view.findViewById(R.id.swipe_container);
        mSwipeRefreshLayout.setProgressViewOffset(false, 0, Util.dip2px(getActivity(), 92));
        //设置刷新时动画的颜色，可以设置4个
        mSwipeRefreshLayout.setColorSchemeResources(android.R.color.holo_blue_light, android.R.color.holo_red_light, android.R.color.holo_orange_light, android.R.color.holo_green_light);
        mSwipeRefreshLayout.setOnRefreshListener(this);
        mSwipeRefreshLayout.setRefreshing(true);

        mRecyclerView = (RecyclerView) view.findViewById(R.id.recycler_view);
        mGridAdapter = new HotsGridAdapter(getActivity(),mHandler);
        mHeaderAndFooterRecyclerViewAdapter = new HeaderAndFooterRecyclerViewAdapter(mGridAdapter);
        mRecyclerView.setAdapter(mHeaderAndFooterRecyclerViewAdapter);

        layoutManager = new GridLayoutManager(getActivity(), 2);
        layoutManager.setSpanSizeLookup(new HeaderSpanSizeLookup((HeaderAndFooterRecyclerViewAdapter) mRecyclerView.getAdapter(), layoutManager.getSpanCount()));
        layoutManager.setOrientation(GridLayoutManager.VERTICAL);
        layoutManager.setSmoothScrollbarEnabled(true);
        mRecyclerView.setHasFixedSize(true);
        mRecyclerView.setLayoutManager(layoutManager);

        headerView = new CommonHeader(getActivity(),R.layout.layout_home_header);
        RecyclerViewUtils.setHeaderView(mRecyclerView, headerView);

        mTitlebar = (RelativeLayout) view.findViewById(R.id.index_title_bar);
        mTitlebar.setVisibility(View.VISIBLE);
        mTitlebar.getBackground().setAlpha(0);
        keyTextView = (TextView) mTitlebar.findViewById(R.id.tv_title);
        mCurCityText = (TextView) mTitlebar.findViewById(R.id.current_city_text);
        categorizeTextView = (TextView) view.findViewById(R.id.image_right);

        slideShowView = (SlideShowView) headerView.findViewById(R.id.slideshowView);
        moreSpecialProduct = headerView.findViewById(R.id.special_more);

        mCurCityText.setOnClickListener(this);
        keyTextView.setOnClickListener(this);
        moreSpecialProduct.setOnClickListener(this);
        categorizeTextView.setOnClickListener(this);

        slideShowView = (SlideShowView) headerView.findViewById(R.id.slideshowView);
        cart_btn = getActivity().findViewById(R.id.shop_cart_btn);
        animation_viewGroup = createAnimLayout();

        imageLoader = ImageLoader.getInstance();
        mRecyclerView.addOnScrollListener(mOnScrollListener);


    }

关键代码：

headerView = new CommonHeader(getActivity(),R.layout.layout_home_header);
        RecyclerViewUtils.setHeaderView(mRecyclerView, headerView);

为RecyclerView添加headerview，headview包括了所有的其他view，如下图所示，所看到的view都包含在headerView里面，不包括titlebar哦。

滑动监听事件：

boolean pauseOnScroll = false, pauseOnFling=true;
    private RecyclerOnScrollListener mOnScrollListener = new RecyclerOnScrollListener() {

        @Override
        public void onScrolled(int dx, int dy) {
            super.onScrolled(dx, dy);
            if (slideShowView.getHeight() > 0) {
                //define it for scroll height
                int lHeight = slideShowView.getHeight();
                if(dy < 0){
                    mTitlebar.getBackground().setAlpha(0);
                }else {
                    if (dy < lHeight) {
                        int progress = (int) (new Float(dy) / new Float(lHeight) * 200);//255
                        mTitlebar.getBackground().setAlpha(progress);
                    } else {
                        mTitlebar.getBackground().setAlpha(255 - 55);
                    }
                }

            }

        }

        @Override
        public void onBottom() {
            super.onBottom();
            Log.d(TAG, "onBottom");
            LoadingFooter.State state = RecyclerViewStateUtils.getFooterViewState(mRecyclerView);
            if(state == LoadingFooter.State.Loading) {
                Log.d(TAG, "the state is Loading, just wait..");
                return;
            }

            if (mCurPageIndex < totalPage) {
                // loading more
                RecyclerViewStateUtils.setFooterViewState(getActivity(), mRecyclerView, REQUEST_COUNT, LoadingFooter.State.Loading, null);
                mHandler.sendEmptyMessage(GET_LIST_DATA);
                Log.d(TAG, "onBottom loading");
            } else {
                //the end
                RecyclerViewStateUtils.setFooterViewState(getActivity(), mRecyclerView, REQUEST_COUNT, LoadingFooter.State.TheEnd, null);
            }
        }

        @Override
        public void onScrollStateChanged(int newState) {
            //根据newState状态做处理
            if (imageLoader != null) {
                switch (newState) {
                    case 0:
                        imageLoader.resume();
                        break;

                    case 1:
                        if (pauseOnScroll) {
                            imageLoader.pause();
                        } else {
                            imageLoader.resume();
                        }
                        break;

                    case 2:
                        if (pauseOnFling) {
                            imageLoader.pause();
                        } else {
                            imageLoader.resume();
                        }
                        break;
                }
            }
        }


    };

代码中涉及到的封装控件下载：http://download.csdn.net/detail/jdsjlzx/9391838，没有demo，请大家自行实现效果。

具体原理请参考

conglida博主写的自定义scrollview 实现标题栏渐变：

http://download.csdn.net/download/conglida/9183723