talk is cheap show me the pictures！

Linearlayoutmanager

另外兩種布局與LinearlayoutManager類似，頭部布局獨(dú)占一行，正常item跟平時(shí)使用的recyclerView一致

sample

demo目錄

enter description here

values目錄下的attrs中添加資源

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="MyRecyclerView">
        <attr name="layout" format="reference"/>
        <attr name="parallaxMultiplier" format="float"/>
    </declare-styleable>
</resources>

使用布局文件中引入控件

    <com.pandaq.collapsingheaderrecyclerview.myrecyclerview.MyRecyclerView
        android:id="@+id/myrecycler"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout="@layout/recycler_header"
        app:parallaxMultiplier="0.8"/>

layout對(duì)應(yīng)的是頭部視圖的布局文件
parallaxMultiplier是滑動(dòng)視差因子默認(rèn)值是1

使用時(shí)寫一個(gè)繼承自BaseRecyclerAdapter類的方法并重寫其中的必要方法onCreate和onBaind

class RecyclerAdapter extends BaseRecyclerAdapter<String> {

    private Context mContext;

    RecyclerAdapter(Context context) {
        mContext = context;
    }

    @Override
    public RecyclerView.ViewHolder onCreate(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(mContext).inflate(R.layout.recycler_item, parent, false);
        return new ViewHolder(view);
    }

    @Override
    public void onBind(RecyclerView.ViewHolder viewHolder, int RealPosition, String data) {
        ViewHolder holder = (ViewHolder) viewHolder;
        holder.mText.setText(data);
    }

     private class ViewHolder extends BaseRecyclerAdapter.Holder {
        @BindView(R.id.text)
        TextView mText;
        ViewHolder(View view) {
            super(view);
            ButterKnife.bind(this, view);
        }
    }
}

使用recyclerView的地方與普通recyclerview一樣，設(shè)置布局，為適配器添加數(shù)據(jù)，設(shè)置適配器

    mMyrecycler.setLayoutManager(new LinearLayoutManager(this));

    adapter.addDatas(dataList);
    mMyrecycler.setAdapter(adapter);

實(shí)現(xiàn)

頭部視圖的滑動(dòng)視差效果是通過(guò)滑動(dòng)的時(shí)候不斷設(shè)置更新頭部的底部margin來(lái)實(shí)現(xiàn)的即MyrecyclerView類中的onScrolled方法的這段代碼

    //當(dāng)添加了頭部視圖且當(dāng)前頭部視圖可見的時(shí)候給頭部視圖添加滾動(dòng)視差效果
    if (headerView != null&&firstVisibleItemPosition == 0) {
        if (distance <= headerView.getHeight()) {                       
            distance = dy;
        } else {
            distance = headerView.getHeight();
        }            
        LayoutParams layoutParams = (LayoutParams) headerView.getLayoutParams();
        //重新賦值給底部邊距
        scrolledMargin = -distance + scrolledMargin;
        if (scrolledMargin > 0) {
            scrolledMargin = 0;
        }
        layoutParams.setMargins(0, 0, 0, (int) (multiplier * scrolledMargin));
        headerView.setLayoutParams(layoutParams);
    }

其中的firstVisibleItemPosition的值 LinearLayoutManager和GridLayoutManager可用findFirstVisibleItemPosition()方法獲取。（PS:findLastVisibleItemPosition()可以獲取最后一個(gè)item的position?？梢杂眠@兩個(gè)方法來(lái)判斷是否滑動(dòng)到底部或頂部，滑動(dòng)是否進(jìn)行加載或刷新）

StaggeredFridLayoutManager則只有findLastVisibleItemPositions（int []positions）和findFirstVisibleItemPositions(int[]positions)方法。這兩個(gè)方法會(huì)將每一頁(yè)顯示的第一個(gè)或者最后一個(gè)item的position放置到傳入的數(shù)組中。取出數(shù)組中的最大最小值則是整個(gè)recyclerView的最后一個(gè)或者第一個(gè)Item的位置

布局兼容

如果不對(duì)Adapter進(jìn)行任何處理像正常使用recyclerView一樣使用會(huì)發(fā)現(xiàn)除了LinearLayoutManager布局會(huì)正常顯示其他兩種方式頭部視圖都是占一個(gè)item的位置而不是一整行。對(duì)于這個(gè)問題我在這兒找到了答案

通過(guò)構(gòu)建一個(gè)繼承自RecyclerView.Adapter<RecyclerView.ViewHolder>的抽象類BaseRecyclerAdapter<T>重寫其中的onAttachedToRecyclerView(RecyclerView recyclerView)方法和onViewAttachedToWindow(RecyclerView.ViewHolder holder)方法來(lái)實(shí)現(xiàn)頭部視圖獨(dú)占一行。使用Adapter的時(shí)候直接繼承這個(gè)類就好了。

    @Override
    public void onAttachedToRecyclerView(RecyclerView recyclerView) {
        super.onAttachedToRecyclerView(recyclerView);

        RecyclerView.LayoutManager manager = recyclerView.getLayoutManager();
        if (manager instanceof GridLayoutManager) {
            final GridLayoutManager gridManager = ((GridLayoutManager) manager);
            gridManager.setSpanSizeLookup(new GridLayoutManager.SpanSizeLookup() {
                @Override
                public int getSpanSize(int position) {
                    return getItemViewType(position) == TYPE_HEADER
                            ? gridManager.getSpanCount() : 1;
                }
            });
        }
    }

    @Override
    public void onViewAttachedToWindow(RecyclerView.ViewHolder holder) {
        super.onViewAttachedToWindow(holder);
        ViewGroup.LayoutParams lp = holder.itemView.getLayoutParams();
        if (lp != null
                && lp instanceof StaggeredGridLayoutManager.LayoutParams
                && holder.getLayoutPosition() == 0) {
            StaggeredGridLayoutManager.LayoutParams p = (StaggeredGridLayoutManager.LayoutParams) lp;
            p.setFullSpan(true);
        }
    }

HeaderView

headerView使用也很簡(jiǎn)單，MyRecyclerView中構(gòu)造了一個(gè)getHeaderView()方法。該方法會(huì)返回一個(gè)View對(duì)象，獲取到這個(gè)對(duì)象之后想怎么處理就隨便你自己發(fā)揮了。我正在寫的這個(gè)項(xiàng)目中headerView就是一個(gè)頂部的ViewPager實(shí)現(xiàn)的輪播Bander，目前還沒有發(fā)現(xiàn)什么不良反應(yīng)。

最后貼上demo下載地址