结合 MultiType 实现加载更多

MultiType 是一个分发管理类,帮助我们轻松实现复杂布局.建议大家阅读源码,作者的思路并不复杂但很巧妙.

下面附上主要源码:

public class LoadMoreDelegate {

    private Items mItems;

    private MultiTypeAdapter mMultiTypeAdapter;
    private OnLoadMoreListener mOnLoadMoreListener;
    private ScrollListener mScrollListener;


    public LoadMoreDelegate(MultiTypeAdapter multiTypeAdapter, Items items, OnLoadMoreListener onLoadMoreListener) {
        mMultiTypeAdapter = multiTypeAdapter;
        mItems = items;
        this.mOnLoadMoreListener = onLoadMoreListener;
    }

    public void attach(RecyclerView recyclerView) {
        LinearLayoutManager linearLayoutManager = (LinearLayoutManager) recyclerView.getLayoutManager();
        mScrollListener = new ScrollListener(mMultiTypeAdapter, mItems, linearLayoutManager, mOnLoadMoreListener);
        recyclerView.addOnScrollListener(mScrollListener);
    }

    public void loadMoreComplete() {
        mScrollListener.setLoading(false);
    }

    public void addData(Items items) {
        int originSize = mItems.size() - 1;
        mItems.remove(originSize);//删除"加载更多"
        mItems.addAll(items);//添加新数据
        //从最后的位置插入新数据
        mMultiTypeAdapter.notifyItemRangeInserted(originSize, items.size() - 1);
    }

    public interface OnLoadMoreListener {
        void onLoadMore();
    }

    private static class ScrollListener extends RecyclerView.OnScrollListener {
        private final int size = 2;
        private boolean mLoading = false;
        private Items mItems;
        private final LoadMore mLoadMore = new LoadMore();

        private LinearLayoutManager mLinearLayoutManager;
        private OnLoadMoreListener mOnLoadMoreListener;
        private MultiTypeAdapter mMultiTypeAdapter;

        ScrollListener(MultiTypeAdapter multiTypeAdapter, Items datas, LinearLayoutManager linearLayoutManager, OnLoadMoreListener onLoadMoreListener) {
            mItems = datas;
            mMultiTypeAdapter = multiTypeAdapter;
            this.mLinearLayoutManager = linearLayoutManager;
            this.mOnLoadMoreListener = onLoadMoreListener;
        }

        @Override
        public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
            if (dy < 0) {//下滑忽略
                return;
            }
            int totalNum = mLinearLayoutManager.getItemCount();
            int lastVisiblePosition = mLinearLayoutManager.findLastCompletelyVisibleItemPosition();
            if (!mLoading && lastVisiblePosition == totalNum - size) {//最后可见的view的位置为倒数第size个,触发加载更多
                mLoading = true;
                mItems.add(mLoadMore);
                mMultiTypeAdapter.notifyItemInserted(mItems.size() - 1);
                mOnLoadMoreListener.onLoadMore();
            }
        }

        void setLoading(boolean loading) {
            this.mLoading = loading;
        }
    }

}

这里提下有些加载更多只是简单的直接使用 notifyDataSetChanged() 方法,效率上我没有研究过,不敢说哪个效率更好,但至少 RecycleView 给我们提供的动画效果没有了,所以建议还是采用 notifyItemInserted().

完整示例:multitypeloadmore

public class PullUpTestActivity extends AppCompatActivity implements LoadMoreDelegate.OnLoadMoreListener {

    private Items mItems = new Items();

    private LoadMoreDelegate mLoadMoreDelegate;
    @Bind(R.id.show)
    RecyclerView mShow;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_pull_up);
        ButterKnife.bind(this);
        for (int i = 0; i < 20; i++) {
            mItems.add("data***" + i);
        }


        MultiTypeAdapter multiTypeAdapter = new MultiTypeAdapter(mItems);
        multiTypeAdapter.register(String.class, new NormalViewProvider());
        multiTypeAdapter.register(LoadMore.class, new LoadMoreViewProvider());
        mShow.setLayoutManager(new LinearLayoutManager(this));
        mShow.setAdapter(multiTypeAdapter);
        mLoadMoreDelegate = new LoadMoreDelegate(multiTypeAdapter, mItems, this);
        mLoadMoreDelegate.attach(mShow);
    }

    @Override
    public void onLoadMore() {
        getMore();
    }

    private void getMore() {
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    Thread.sleep(2000);
                    runOnUiThread(new Runnable() {
                        @Override
                        public void run() {
                            Items strings = new Items();
                            for (int i = 0; i < 20; i++) {
                                strings.add("data***more" + i);
                            }
                            mLoadMoreDelegate.addData(strings);
                            mLoadMoreDelegate.loadMoreComplete();
                        }
                    });

                } catch (InterruptedException e) {
                    e.printStackTrace();
                }


            }
        }).start();
    }
}

还有一点提一下,这样的必须需要滑动界面才可以触发加载更多,如果第一屏数据不超过一屏,将没法触发加载更多.但这样我认为是合理的,如果第一页数据的请求就不满一屏,所以后面应该是在没有数据的.有些加载更多的实现是一到最后一个数据,就开始加载更多.但在第一页数据不满一屏的情况下,触发了加载很多,很违背直觉. BaseRecyclerViewAdapterHelper 就采用了这种实现,大家可以去看源码. 而且一般第一页的请求,我们一般会有自己的一个 loading 视图,这样不满一屏的情况下,还有一个加载更多的视图,这是不太合理的.

以上 demo 仅供参考,大家可以进一步自己封装和实现.可以自己实现个 MultiTypeAdapter 并把代码整合到里面去,这样用起来可能会更方便点.

效果图

loadmore.gif