问题分析的步骤：
如何使用原理分析 如何该框架的分组功能
Adapter:public class SectionAdapter extends BaseSectionQuickAdapter<MySection> { public SectionAdapter(int layoutResId, int sectionHeadResId, List data) { super(layoutResId, sectionHeadResId, data); } @Override protected void convert(BaseViewHolder helper, MySection item) { helper.setImageUrl(R.id.iv, (String) item.t); } @Override protected void convertHead(BaseViewHolder helper,final MySection item) { helper.setText(R.id.header, item.header); } adapter的构造需要传入三个参数，分别是内容的布局和头部的布局和数据源，数据源需要继承SectionEntity如下：
Entity:public class MySection extends SectionEntity<Video> { public MySection(boolean isHeader, String header, boolean isMroe) { super(isHeader, header); } public MySection(Video t) { super(t); } }填充数据public static List<MySection> getSampleData() { List<MySection> list = new ArrayList<>(); list.add(new MySection(true, "Section 1")); list.add(new MySection(new Video(HTTPS_AVATARS1_GITHUBUSERCONTENT_COM_LINK, CYM_CHAD))); list.add(new MySection(new Video(HTTPS_AVATARS1_GITHUBUSERCONTENT_COM_LINK, CYM_CHAD))); list.add(new MySection(new Video(HTTPS_AVATARS1_GITHUBUSERCONTENT_COM_LINK, CYM_CHAD))); list.add(new MySection(new Video(HTTPS_AVATARS1_GITHUBUSERCONTENT_COM_LINK, CYM_CHAD))); list.add(new MySection(true, "Section 2")); list.add(new MySection(new Video(HTTPS_AVATARS1_GITHUBUSERCONTENT_COM_LINK, CYM_CHAD))); list.add(new MySection(new Video(HTTPS_AVATARS1_GITHUBUSERCONTENT_COM_LINK, CYM_CHAD))); list.add(new MySection(new Video(HTTPS_AVATARS1_GITHUBUSERCONTENT_COM_LINK, CYM_CHAD))); list.add(new MySection(true, "Section 3")); list.add(new MySection(new Video(HTTPS_AVATARS1_GITHUBUSERCONTENT_COM_LINK, CYM_CHAD))); list.add(new MySection(new Video(HTTPS_AVATARS1_GITHUBUSERCONTENT_COM_LINK, CYM_CHAD))); list.add(new MySection(true, "Section 4")); list.add(new MySection(new Video(HTTPS_AVATARS1_GITHUBUSERCONTENT_COM_LINK, CYM_CHAD))); list.add(new MySection(new Video(HTTPS_AVATARS1_GITHUBUSERCONTENT_COM_LINK, CYM_CHAD))); list.add(new MySection(true, "Section 5")); list.add(new MySection(new Video(HTTPS_AVATARS1_GITHUBUSERCONTENT_COM_LINK, CYM_CHAD))); list.add(new MySection(new Video(HTTPS_AVATARS1_GITHUBUSERCONTENT_COM_LINK, CYM_CHAD))); return list;} 原理分析 其实头部和内容部分就是通过不同的type来实现的，我们可以查看BaseSectionQuickAdapter源码
@Override protected int getDefItemViewType(int position) { return ((SectionEntity) mData.get(position)).isHeader ? SECTION_HEADER_VIEW : 0; } 它是通过SectionEntity的isHeader属性来区别是否是头部的
public abstract class SectionEntity<T> { public boolean isHeader; public T t; public String header; public SectionEntity(boolean isHeader, String header) { this.isHeader = isHeader; this.header = header; this.t = null; } public SectionEntity(T t) { this.isHeader = false; this.header = null; this.t = t; }} 这就是为什么要求开发者的实体类必须继承SectionEntity的原因了，因为需要通过它的isHeader这个属性来改变type，onCreateViewHolder通过不同的type来加载不同的布局。
@Overrideprotected BaseViewHolder onCreateDefViewHolder(ViewGroup parent, int viewType) { if (viewType == SECTION_HEADER_VIEW) return new BaseViewHolder(getItemView(mSectionHeadResId, parent)); return super.onCreateDefViewHolder(parent, viewType);} 然后在onBindViewHolder里面通过type来区分头部和内容部分调用不同的方法
protected void convert(BaseViewHolder holder, Object item) { switch (holder.getItemViewType()) { case SECTION_HEADER_VIEW: setFullSpan(holder); convertHead(holder, (T) item); break; default: convert(holder, (T) item); break; }}protected abstract void convertHead(BaseViewHolder helper, T item);protected abstract void convert(BaseViewHolder helper, T item); 在此有同学肯定会想这个setFullSpan方法是干嘛的呀？
因为要考虑到RecyclerView的setLayoutManager的三种不同类型的LayoutManager
LinearLayoutManagerGridLayoutManagerStaggeredGridLayoutManager LinearLayoutManager：本身就可以占据一行，所以不需要做特殊的处理
GridLayoutManager：需要特殊处理,才能实现头部占据一行的效果，代码如下：
@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) { int type = getItemViewType(position); return (type == SECTION_HEADER_VIEW) ? gridManager.getSpanCount() : 1; }); } } StaggeredGridLayoutManager：需要特殊处理,才能实现头部占据一行的效果，代码如下：
protected void setFullSpan(RecyclerView.ViewHolder holder) { if (holder.itemView.getLayoutParams() instanceof StaggeredGridLayoutManager.LayoutParams) { StaggeredGridLayoutManager.LayoutParams params = (StaggeredGridLayoutManager.LayoutParams) holder.itemView.getLayoutParams(); params.setFullSpan(true); } } 这就是为什么要在conver方法里判断是head类型的代码块中要调用setFullSpan方法的原因了。
如果还什么疑问都可以在这里进行提问 因为开源项目和技术分享收到 Google 的面试邀请，大家有什么想要讨论的么？