MultiType 是一個(gè)分發(fā)管理類,幫助我們輕松實(shí)現(xiàn)復(fù)雜布局.建議大家閱讀源碼,作者的思路并不復(fù)雜但很巧妙.

下面附上主要源碼:

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);//刪除"加載更多"
        mItems.addAll(items);//添加新數(shù)據(jù)
        //從最后的位置插入新數(shù)據(jù)
        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) {//最后可見(jiàn)的view的位置為倒數(shù)第size個(gè),觸發(fā)加載更多
                mLoading = true;
                mItems.add(mLoadMore);
                mMultiTypeAdapter.notifyItemInserted(mItems.size() - 1);
                mOnLoadMoreListener.onLoadMore();
            }
        }

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

}

這里提下有些加載更多只是簡(jiǎn)單的直接使用 notifyDataSetChanged() 方法,效率上我沒(méi)有研究過(guò),不敢說(shuō)哪個(gè)效率更好,但至少 RecycleView 給我們提供的動(dòng)畫效果沒(méi)有了,所以建議還是采用 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();
    }
}

還有一點(diǎn)提一下,這樣的必須需要滑動(dòng)界面才可以觸發(fā)加載更多,如果第一屏數(shù)據(jù)不超過(guò)一屏,將沒(méi)法觸發(fā)加載更多.但這樣我認(rèn)為是合理的,如果第一頁(yè)數(shù)據(jù)的請(qǐng)求就不滿一屏,所以后面應(yīng)該是在沒(méi)有數(shù)據(jù)的.有些加載更多的實(shí)現(xiàn)是一到最后一個(gè)數(shù)據(jù),就開始加載更多.但在第一頁(yè)數(shù)據(jù)不滿一屏的情況下,觸發(fā)了加載很多,很違背直覺(jué). BaseRecyclerViewAdapterHelper 就采用了這種實(shí)現(xiàn),大家可以去看源碼. 而且一般第一頁(yè)的請(qǐng)求,我們一般會(huì)有自己的一個(gè) loading 視圖,這樣不滿一屏的情況下,還有一個(gè)加載更多的視圖,這是不太合理的.

以上 demo 僅供參考,大家可以進(jìn)一步自己封裝和實(shí)現(xiàn).可以自己實(shí)現(xiàn)個(gè) MultiTypeAdapter 并把代碼整合到里面去,這樣用起來(lái)可能會(huì)更方便點(diǎn).

效果圖

loadmore.gif