RecycleView 添加底部加载更多

在阅读此文章前 请先看 http://blog.csdn.net/fangchao3652/article/details/43148871

与开头的连接文章思想类似，只不过那个是图片文字按钮等多种布局的混排，而添加底部只是普通Item 与底部Item两种布局的混排。那个是根据bean中的类型进行判断，然后在onCreateViewholder方法中创建不同的viewholder。而此文章先是根据getItemViewType方法判断item是哪中类型，然后成相应的viewholder.
那么我们就先来看一下getItemViewType方法：

  @Override
    public int getItemViewType(int position) {

        if (position == getContentItemCount() && useFooter()) {
            return TYPE_FOOTER;//若是最底下的item加载 footerviewholder
        }
        return Type_putong;//其他正常的item 
    }

然后就是onCreateViewHolder了(里面的两个方法等会贴出)

  @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        if (viewType == TYPE_FOOTER) {
            return onCreateFooterViewHolder(parent, viewType);
        }
        return onCreateContentItemViewHolder(parent, viewType - TYPE_ADAPTEE_OFFSET);
    }

既然创建了不同的viewholder 那绑定的时候也要根据 刚才的返回的viewholder的类型分别绑定：

  @Override
    public final void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        super.onBindViewHolder(holder,position);
        if (position == getContentItemCount() && holder.getItemViewType() == TYPE_FOOTER) {
            onBindFooterView(holder, position);//绑定底部item （可见性·赋值。。。）
        } else {
            onBindContentItemView(holder, position);//绑定普通的item
        }
    }
    //getContentItemCount 是在子类中实现的，获取全部数据的个数

好了主要的就这几个，好了，贴出完整代码：

//用的时候要继承此抽象类，然后实现里面的几个抽象方法即可。
public abstract class FooterAdapter extends BaseAnimAdapter{

    private static final int TYPE_FOOTER = Integer.MIN_VALUE;
    private static final int TYPE_ADAPTEE_OFFSET = 2;
    private boolean canLoadMore = false;

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        if (viewType == TYPE_FOOTER) {
            return onCreateFooterViewHolder(parent, viewType);
        }
        return onCreateContentItemViewHolder(parent, viewType - TYPE_ADAPTEE_OFFSET);
    }

    @Override
    public final void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        super.onBindViewHolder(holder,position);
        if (position == getContentItemCount() && holder.getItemViewType() == TYPE_FOOTER) {
            onBindFooterView(holder, position);
        } else {
            onBindContentItemView(holder, position);
        }
    }

    private static class ViewHolderFooter extends RecyclerView.ViewHolder {
        public ProgressBar pro;
        public TextView title;

        public ViewHolderFooter(View v) {
            super(v);
            pro = (ProgressBar) v.findViewById(R.id.pro);
            title = (TextView) v.findViewById(R.id.footerTitle);
        }
    }

    @Override
    public int getItemCount() {
        int itemCount = getContentItemCount();
        if (useFooter()) {
            itemCount += 1;
        }
        return itemCount;
    }

    @Override
    public int getItemViewType(int position) {

        if (position == getContentItemCount() && useFooter()) {
            return TYPE_FOOTER;
        }
        return getContentItemType(position) + TYPE_ADAPTEE_OFFSET;
    }

    public void setCanLoadMore(boolean canLoadMore){
        this.canLoadMore = canLoadMore;
    }

    public boolean isCanLoadMore() {
        return canLoadMore;
    }

    public abstract boolean useFooter();

    public RecyclerView.ViewHolder onCreateFooterViewHolder(ViewGroup parent, int viewType){
        View v = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.footerview, parent, false);
        ViewHolderFooter vh = new ViewHolderFooter(v);
        return vh;
    }

    public void onBindFooterView(RecyclerView.ViewHolder holder, int position){
        ViewHolderFooter footerHolder = (ViewHolderFooter) holder;
        if (isCanLoadMore()) {
            footerHolder.pro.setVisibility(View.VISIBLE);
            footerHolder.title.setText("加载更多");
        } else {
            footerHolder.pro.setVisibility(View.GONE);
            footerHolder.title.setText("已到底部");
        }
    }

    public abstract RecyclerView.ViewHolder onCreateContentItemViewHolder(ViewGroup parent, int viewType);//创建你要的普通item 

    public abstract void onBindContentItemView(RecyclerView.ViewHolder holder, int position);//绑定数据

    public abstract int getContentItemCount();

    public abstract int getContentItemType(int position);//没用到，返回0即可，为了扩展用的
}

对了，他还有个父类，主要是定义了一个记载时的动画，看一下吧：

public abstract class BaseAnimAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder>{
    private int lastPosition = -1;

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        setAnimation(holder.itemView, position);

    }

    private void setAnimation(View viewToAnimate, int position) {
        if (position > lastPosition) {
            Animation animation = AnimationUtils.loadAnimation(viewToAnimate.getContext(), R.anim.item_slide_bottom_up);
            viewToAnimate.startAnimation(animation);
            lastPosition = position;
        }
    }
}

到这布局控件什么的都有了，怎么上拉加载数据呢？我们来个监听器，并暴露一个onloadmore的抽象方法：

public abstract class RecyclerOnScrollListener extends RecyclerView.OnScrollListener {
    public static String TAG = RecyclerOnScrollListener.class.getSimpleName();
    private LinearLayoutManager manager;
    //用来标记是否正在向最后一个滑动，既是否向右滑动或向下滑动
    boolean isSlidingToLast = false;

    public RecyclerOnScrollListener(LinearLayoutManager linearLayoutManager) {
        this.manager = linearLayoutManager;
    }

    @Override
    public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
        // 当不滚动时
        if (newState == RecyclerView.SCROLL_STATE_IDLE) {
            //获取最后一个完全显示的ItemPosition
            int lastVisibleItem = manager.findLastCompletelyVisibleItemPosition();
            int totalItemCount = manager.getItemCount();

            // 判断是否滚动到底部，并且是向右滚动
            if (lastVisibleItem == (totalItemCount - 1) && isSlidingToLast) {
                //加载更多功能的代码
                onLoadMore();
            }
        }
    }

    @Override
    public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
        super.onScrolled(recyclerView, dx, dy);
        //dx用来判断横向滑动方向，dy用来判断纵向滑动方向
        if (dx > 0 || dy > 0) {
            //大于0表示，正在向右滚动
            isSlidingToLast = true;
        } else {
            //小于等于0 表示停止或向左滚动
            isSlidingToLast = false;
        }

    }


    public abstract void onLoadMore();//要在实现类中实现

}

ok了，最后贴个demo吧：

@EActivity(R.layout.activity_recycler_view)
public class RecyclerViewActivity extends BaseActionBarActivity implements SwipeRefreshLayout.OnRefreshListener {
    @ViewById(R.id.swipe_container)
    SwipeRefreshLayout mSwipeLayout;
    @ViewById(R.id.recycler_view)
    RecyclerView mRecyclerView;
    private RecyclerViewAdapter mAdapter;
    private LinearLayoutManager mLayoutManager;
   List<String> myDataset;

    @AfterViews
    void initView() {

        //下拉刷新属性设置
        mSwipeLayout = (SwipeRefreshLayout) findViewById(R.id.swipe_container);
        mSwipeLayout.setOnRefreshListener(this);
        mSwipeLayout.setColorSchemeResources(android.R.color.holo_blue_bright,
                android.R.color.holo_green_light, android.R.color.holo_orange_light,
                android.R.color.holo_red_light);
        //设置固定大小
//        mRecyclerView.setHasFixedSize(true);
      /*  //设置item动画
        mRecyclerView.setItemAnimator(new SlideInOutBottomItemAnimator(mRecyclerView));

        mRecyclerView.addItemDecoration(new DividerItemDecoration(this, LinearLayoutManager.VERTICAL));
*/
        //设置显示布局方式
        mLayoutManager = new LinearLayoutManager(this);
        mLayoutManager.setOrientation(LinearLayoutManager.VERTICAL);
        mRecyclerView.setLayoutManager(mLayoutManager);
        mRecyclerView.setOnScrollListener(new RecyclerOnScrollListener(mLayoutManager) {
            @Override
            public void onLoadMore() {


if(myDataset.size()<50) {
    myDataset.add("ccccc");
    myDataset.add("ccccc");
    myDataset.add("ccccc");
    myDataset.add("ccccc");
    myDataset.add("ccccc");
    myDataset.add("ccccc");
    myDataset.add("ccccc");
    myDataset.add("ccccc");
    mAdapter.setCanLoadMore(true);
}else
mAdapter.setCanLoadMore(false);
                mAdapter.notifyDataSetChanged();
            }
        });
        // specify an adapter (see also next example)
        myDataset = new ArrayList<>();
        myDataset.add("aa");
        myDataset.add("aa");
        myDataset.add("aa");
        myDataset.add("aa");
        myDataset.add("aa");
        myDataset.add("aa");
        myDataset.add("aa");
        myDataset.add("aa");
        myDataset.add("aa");
        myDataset.add("aa");
        myDataset.add("aa");
        myDataset.add("aa");
        myDataset.add("aa");
        myDataset.add("aa");
        myDataset.add("aa");
        mAdapter = new RecyclerViewAdapter(myDataset);
        mAdapter.setCanLoadMore(true);
        mRecyclerView.setAdapter(mAdapter);

    }

    @Override
    public void onRefresh() {
        new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {
                mSwipeLayout.setRefreshing(false);

//                mAdapter.notifyDataSetChanged();
                mAdapter.notifyItemInserted(0);
            }
        }, 2000);
    }


}