下拉刷新，上拉加载，在Android项目中可谓是随处可见，其实现方式也是各种各样。今天介绍一个android support v4包下提供的下拉刷新控件SwipeRefreshLayout,个人觉得这个还是比较好看的

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一、下拉刷新

看看知乎中的下拉刷新效果图：

SwipeRefreshLayout【截图来自：知乎app】

如何使用

//xml布局
<android.support.v4.widget.SwipeRefreshLayout
    android:id="@+id/wifi_swipe_refresh"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_below="@+id/fl_title">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/rv_wifi_table"
        android:layout_width="match_parent"
         android:layout_height="match_parent" />
    </android.support.v4.widget.SwipeRefreshLayout>

//Activity中使用
wifi_swipe_refresh = (SwipeRefreshLayout) findViewById(R.id.wifi_swipe_refresh);
wifi_swipe_refresh.setOnRefreshListener(this);//SwipeRefreshLayout.OnRefreshListener
wifi_swipe_refresh.setColorSchemeResources(
                R.color.google_blue,
                R.color.google_green,
                R.color.google_red,
                R.color.google_yellow
    );

上述监听事件（这里使用 RxJava实现定时操作）

    @Override
    public void onRefresh() {
        Observable.timer(1, TimeUnit.SECONDS, AndroidSchedulers.mainThread()).map(new Func1<Long, Object>() {
            @Override
            public Object call(Long aLong) {
                initData();
                if (null != wifi_swipe_refresh) {
                    wifi_swipe_refresh.setRefreshing(false);
                }
                return null;
            }
        }).subscribe();
    }   
    

进入时加载circleview 加载动画：

1、默认setRefreshing(true)方法，无法实线初次加载显示动画的效果。我们可以这样处理：

    swipeRefreshLayout.setProgressViewOffset(false, 0,
        (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 24, getResources().
        getDisplayMetrics()));
    swipeRefreshLayout.setRefreshing(true);.0

2、使用swipeRefreshLayout.post()方式来加载显示动画

    swipeRefreshLayout.post(new Runnable() {
        @Override
        public void run() {
            swipeRefreshLayout.setRefreshing(true);
        }
    });

关闭circleview 加载动画：

由于子线程中不能更新UI，所以需要通过hander来定时关闭加载动画

使用handler计时 定时关闭

    final Handler handler = new Handler();

    handler.postDelayed(new Runnable() {
        @Override
        public void run() {
            swipeRefreshLayout.setRefreshing(false);
        }
    },2000);//2000ms后取消（关闭）

避免刷新过程中仍可以操作界面,自定义SwipeRefreshLayout，通过父类拿到refresh状态，从而进行事件的传递机制控制

public class MySwipeRefreshLayout extends SwipeRefreshLayout {
    public MySwipeRefreshLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
    }
    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        if (super.isRefreshing()) {//调用父view中的isRefreshing（）方法，从而拿到刷新状态。刷新时消化点击事件
            return true;
        }
        return super.onInterceptTouchEvent(ev);
    }
}

二、上拉加载(滑到底部自动加载)

滑动底部，自动加载

结合HeaderViewRecyclerAdapter

private void initView() {
        firstCreateFootView = true;//首次加载headview，headview始终只能创建一次

        manager = new LinearLayoutManager(getActivity());
        manager.setOrientation(LinearLayoutManager.VERTICAL);
        recyclerView_fans.setLayoutManager(manager);

        adapter = new FansInfoAdapter(getActivity());
        /**
         * 核心代码：RecyclerView.Adapter的adapter作为参数，初始化HeaderViewRecyclerAdapter
         * headerViewRecyclerAdapter才是作为RecyclerView的adapter，也是在这一步完成绑定headerView
         */
        headerViewRecyclerAdapter = new HeaderViewRecyclerAdapter(adapter);
        recyclerView_fans.setAdapter(headerViewRecyclerAdapter);
        recyclerView_fans.addOnScrollListener(new RecyclerView.OnScrollListener() {
            @Override
            public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
                super.onScrolled(recyclerView, dx, dy);
                int lastVisiableItemPosition = manager.findLastVisibleItemPosition();
                if (lastVisiableItemPosition + 1 == headerViewRecyclerAdapter.getItemCount() && headerViewRecyclerAdapter.getItemCount() >= pageSize) {
                    LogUtil.i("info", "滑动到底了pos:" + lastVisiableItemPosition);
                    //执行加载更多数据
                    simulateLoadMoreData();
                }
            }
        });

        /**
         * 下拉刷新监听
         */
        swipe_refresh_layout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
            @Override
            public void onRefresh() {
                Observable.timer(1, TimeUnit.SECONDS, AndroidSchedulers.mainThread()).map(new Func1<Long, Object>() {
                    @Override
                    public Object call(Long aLong) {
                        initData();
                        swipe_refresh_layout.setRefreshing(false);
                        headerViewRecyclerAdapter.notifyDataSetChanged();
//                        ToastUtils.show(getActivity(), "刷新成功");
                        return null;
                    }
                }).subscribe();
            }
        });
    }

核心的点在于何时去创建底部的headerview，这很有讲究，因为我们这里做的是滑动到底部自动加载更多数据，因此判断这个临界点成为核心，解决思路：从每次的请求网络数据回调中判断数据条目是否满一页即是否等于pageSize,瞒着条件即可调用创建hederview方法，动态添加headerview，注意：全程只可以创建一次，因此这边还要控制好。

    //第一次网络请求，数据回调时进行判断，满足条件才创建
    private void createLoadMoreView() {
        if (getActivity() == null) {
            return;
        }
        //headerView 布局可以自行定义
        View loadMoreView = LayoutInflater.from(getActivity()).inflate(R.layout.item_view_load_more, recyclerView_fans, false);
        headerViewRecyclerAdapter.addFooterView(loadMoreView);
    }

同时当数据已加载全部时还需要将headerview隐藏（remove）

      //此处进行判断，满足条件时调用headerViewRecyclerAdapter.notifyItemRemoved(headerViewRecyclerAdapter.getItemCount());去掉headerview
      if (null != fansCardTableBeen.get(0).getUser_phone() && fansCardTableBeen.get(0).getUser_phone().equals("")) {//已滑到最后一页
                        if (currentPage != 0) {
                            currentPage--;
                            ToastUtils.show(getActivity(), "没有更多数据");
                            headerViewRecyclerAdapter.notifyItemRemoved(headerViewRecyclerAdapter.getItemCount());
                        } else {
                            tv_empty_data.setVisibility(View.VISIBLE);
                            recyclerView_fans.setVisibility(View.GONE);
                        }
                    } else {
                        for (FansCardTableBean bean : fansCardTableBeen) {
                            list.add(bean);
                        }
                        adapter.setData(list);
                        adapter.notifyDataSetChanged();
                    }
      }

这里贴上HeaderViewRecyclerAdapter 源码(来源于网络博友博客)

/** * Created by Android Studio * User: Ailurus(ailurus@foxmail.com) * Date: 2015-10-26 * Time: 18:23 */
public class HeaderViewRecyclerAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {

    private static final int HEADERS_START = Integer.MIN_VALUE;
    private static final int FOOTERS_START = Integer.MIN_VALUE + 10;
    private static final int ITEMS_START = Integer.MIN_VALUE + 20;
    private static final int ADAPTER_MAX_TYPES = 100;

    private RecyclerView.Adapter mWrappedAdapter;
    private List<View> mHeaderViews, mFooterViews;
    private Map<Class, Integer> mItemTypesOffset;

    public HeaderViewRecyclerAdapter(RecyclerView.Adapter adapter) {
        mHeaderViews = new ArrayList<>();
        mFooterViews = new ArrayList<>();
        mItemTypesOffset = new HashMap<>();
        setWrappedAdapter(adapter);
    }

    public void setAdapter(RecyclerView.Adapter adapter) {
        if (mWrappedAdapter != null && mWrappedAdapter.getItemCount() > 0) {
            notifyItemRangeRemoved(getHeaderCount(), mWrappedAdapter.getItemCount());
        }
        setWrappedAdapter(adapter);
        notifyItemRangeInserted(getHeaderCount(), mWrappedAdapter.getItemCount());
    }

    @Override
    public int getItemViewType(int position) {
        int hCount = getHeaderCount();
        if (position < hCount) return HEADERS_START + position;
        else {
            int itemCount = mWrappedAdapter.getItemCount();
            if (position < hCount + itemCount) {
                return getAdapterTypeOffset() + mWrappedAdapter.getItemViewType(position - hCount);
            } else return FOOTERS_START + position - hCount - itemCount;
        }
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup viewGroup, int viewType) {
        if (viewType < HEADERS_START + getHeaderCount())
            return new StaticViewHolder(mHeaderViews.get(viewType - HEADERS_START));
        else if (viewType < FOOTERS_START + getFooterCount())
            return new StaticViewHolder(mFooterViews.get(viewType - FOOTERS_START));
        else {
            return mWrappedAdapter.onCreateViewHolder(viewGroup, viewType - getAdapterTypeOffset());
        }
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder viewHolder, int position) {
        int hCount = getHeaderCount();
        if (position >= hCount && position < hCount + mWrappedAdapter.getItemCount())
            mWrappedAdapter.onBindViewHolder(viewHolder, position - hCount);
    }

    public void addHeaderView(View view) {
        mHeaderViews.add(view);
    }

    public void addFooterView(View view) {
        mFooterViews.add(view);
    }

    @Override
    public int getItemCount() {
        return getHeaderCount() + getFooterCount() + getWrappedItemCount();
    }

    public int getWrappedItemCount() {
        return mWrappedAdapter.getItemCount();
    }

    public int getHeaderCount() {
        return mHeaderViews.size();
    }

    public int getFooterCount() {
        return mFooterViews.size();
    }


    private void setWrappedAdapter(RecyclerView.Adapter adapter) {
        if (mWrappedAdapter != null) mWrappedAdapter.unregisterAdapterDataObserver(mDataObserver);
        mWrappedAdapter = adapter;
        Class adapterClass = mWrappedAdapter.getClass();
        if (!mItemTypesOffset.containsKey(adapterClass)) putAdapterTypeOffset(adapterClass);
        mWrappedAdapter.registerAdapterDataObserver(mDataObserver);
    }


    private void putAdapterTypeOffset(Class adapterClass) {
        mItemTypesOffset.put(adapterClass, ITEMS_START + mItemTypesOffset.size() * ADAPTER_MAX_TYPES);
    }


    private int getAdapterTypeOffset() {
        return mItemTypesOffset.get(mWrappedAdapter.getClass());
    }


    private RecyclerView.AdapterDataObserver mDataObserver = new RecyclerView.AdapterDataObserver() {
        @Override
        public void onChanged() {
            super.onChanged();
            notifyDataSetChanged();
        }

        @Override
        public void onItemRangeChanged(int positionStart, int itemCount) {
            super.onItemRangeChanged(positionStart, itemCount);
            notifyItemRangeChanged(positionStart + getHeaderCount(), itemCount);
        }


        @Override
        public void onItemRangeInserted(int positionStart, int itemCount) {
            super.onItemRangeInserted(positionStart, itemCount);
            notifyItemRangeInserted(positionStart + getHeaderCount(), itemCount);
        }


        @Override
        public void onItemRangeRemoved(int positionStart, int itemCount) {
            super.onItemRangeRemoved(positionStart, itemCount);
            notifyItemRangeRemoved(positionStart + getHeaderCount(), itemCount);
        }


        @Override
        public void onItemRangeMoved(int fromPosition, int toPosition, int itemCount) {
            super.onItemRangeMoved(fromPosition, toPosition, itemCount);
            int hCount = getHeaderCount();
            // TODO: No notifyItemRangeMoved method?
            notifyItemRangeChanged(fromPosition + hCount, toPosition + hCount + itemCount);
        }
    };

    private static class StaticViewHolder extends RecyclerView.ViewHolder {
        public StaticViewHolder(View itemView) {
            super(itemView);
        }
    }
}