ExpandRecycleView

Expand RecycleView 是单个RecycleView 来实现 ExpandableListView 的效果。好处是可以添加展开和搜索动画。我们先看下效果：

展开的动画我用的是默认的，大家需要其他的动画的话，可以自己重写一下动画效果。这里主要看一下代码这么实现以及数据结构的整理。

这是我再做项目的时候，从服务器获取的数据。这个数据，我们再做的时候需要进一步处理。

1：处理数据，设置RecycleView 的布局

       /**
           * 整理数据
           */
          private void initData() {
              String json = new String(getAssertsFile(this, "data.json"));
              Gson gson = new Gson();
              myDataBean = gson.fromJson(json, MyDataBean.class);
              categories = myDataBean.getData().getCategories();
              if (subCategoriesBeansListShow.size() == 0) {
                  int size = categories.size();
                  //1：遍历大集合 categories (下面叫一级分类)  SubCategories（下面叫二级分类）
                  for (int i = 0; i < size; i++) {
                      MyDataBean.DataBean.CategoriesBean categoriesBean = categories.get(i);
                      //2：创建二级分类对象，把一级分类的数据（name:aaaaaaa）放到二级分类对象中，并设置title为true
                      MyDataBean.DataBean.CategoriesBean.SubCategoriesBean subCategoriesBean = new MyDataBean.DataBean.CategoriesBean.SubCategoriesBean();
                      subCategoriesBean.setName(categoriesBean.getName());
                      subCategoriesBean.setTitle(true);
                      subCategoriesBean.setTitleOldListPos(i);
                      //3:创建二级分类对象，把一级分类的数据（introduce:bbbbbbb）放到二级分类对象中,并设置子View 的title为true
                      MyDataBean.DataBean.CategoriesBean.SubCategoriesBean subCategoriesBean2 = new MyDataBean.DataBean.CategoriesBean.SubCategoriesBean();
                      subCategoriesBean2.setName(categoriesBean.getIntroduce());
                      subCategoriesBean2.setChildTitle(true);
                      //4:把子View 的title 放到二级分类第一个
                      categoriesBean.getSub_categories().add(0, subCategoriesBean2);
                      //5：创建一个三级分类集合，放入我们创建的第一个二级分类对象
                      subCategoriesBeansListShow.add(subCategoriesBean);
                  }
                  rvExpand.setLayoutManager(new LinearLayoutManager(this));
                  homeCategoriesAdapter = new HomeCategoriesAdapter(this, categories, subCategoriesBeansListShow, this);
              }
              rvExpand.setAdapter(homeCategoriesAdapter);
              //以下是对布局进行控制，3表示3个条目做为一行
              final GridLayoutManager manager = new GridLayoutManager(this, 3);
              manager.setSpanSizeLookup(new GridLayoutManager.SpanSizeLookup() {
                  @Override
                  public int getSpanSize(int position) {
                      //如果条目的 type 是 1 ， 那么这个条目就占3个位置。也就是一行
                      if (homeCategoriesAdapter.getItemViewType(position) == 1) {
                          return 3;
                          //如果条目的 type 是 2 ， 那么这个条目就占3个位置。也就是一行
                      } else if (homeCategoriesAdapter.getItemViewType(position) == 2) {
                          return 3;
                      } else {
                          return 1;
                      }
                  }
              });
              rvExpand.setLayoutManager(manager);
          }

2：在Adapter里面根据 type 填充布局

      @Override
          public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
              View itemView;
              if (viewType == 1) {
                  itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_home_categories, parent, false);
                  return new ViewHolder(itemView);
              } else if (viewType == 2 ) {
                  itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.categories_header, parent, false);
                  return new ViewHolderChildTitle(itemView);
              } else {
                  itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_home_categories_gridview1, parent, false);
                  return new ViewHolder1(itemView);
              }
          }

3：如何优雅的为横向排列的 item 设置间距。

  //计算出横向排列的数据的大小 size (减1是减掉type = 2的情况)
        int size = categories.get(titleOldListPos).getSub_categories().size()-1;
        //每行是3个 就 %3  如果等于0   结果就是行数，
        if (size % 3 == 0) {
            pos = size / 3;
        } else {
            //如果不等于0  先将结果转为int 然后加一
            pos = size / 3 + 1;
        }
        //postion - 3*行数 = 2+titleOldListPos  如果等式成立表示第一列
        //postion - 3*行数 = 3+titleOldListPos  如果等式成立表示第二列
        //postion - 3*行数 = 4+titleOldListPos  如果等式成立表示第三列
        for (int i = 0; i <= pos; i++) {
            if (position - 3 * i == titleOldListPos + 2) {
                RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.MATCH_PARENT, RelativeLayout.LayoutParams.WRAP_CONTENT);
                layoutParams.setMargins(30, 0, 10, 30);
                itemSectionHolder.item_categories_relas.setLayoutParams(layoutParams);
            } else if (position - 3 * i == titleOldListPos + 3) {
                RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.MATCH_PARENT, RelativeLayout.LayoutParams.WRAP_CONTENT);
                layoutParams.setMargins(10, 0, 10, 30);
                itemSectionHolder.item_categories_relas.setLayoutParams(layoutParams);
            } else if (position - 3 * i == titleOldListPos + 4) {
                RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.MATCH_PARENT, RelativeLayout.LayoutParams.WRAP_CONTENT);
                layoutParams.setMargins(10, 0, 30, 30);
                itemSectionHolder.item_categories_relas.setLayoutParams(layoutParams);
            }
        }

4：如何展开和收起布局

  /**
       * 展开某个item
       *
       * @param titleIndex 点击的title的position,还需要这个position在categories集合下面的角标时多少。这里算出来
       */
      private void expand(int titleIndex, int categoriesPos) {
          categoriesBeanListShow.addAll(categoriesPos + 1, categories.get(categoriesPos).getSub_categories());
          curExpandChapterIndex = categoriesPos;
          categories.get(categoriesPos).setExpand(true);
          notifyItemRangeInserted(categoriesPos + 1, categories.get(categoriesPos).getSub_categories().size());
          notifyItemRangeChanged(0, getItemCount(), "change_position");
      }

      /**
       * 收起某个item
       *
       * @param titleIndex
       */
      private void narrow(int titleIndex) {
          if (titleIndex != -1) {
              int removeStart = titleIndex + 1;
              int removeCount = 0;
              for (int i = removeStart; i < categoriesBeanListShow.size() && (getItemViewType(i) == 3 || getItemViewType(i) == 2); i++) {
                  removeCount++;
              }
              categoriesBeanListShow.removeAll(categories.get(titleIndex).getSub_categories());
              categories.get(titleIndex).setExpand(false);
              notifyItemRangeRemoved(removeStart, removeCount);
              notifyItemRangeChanged(0, getItemCount(), "change_position");
          }
      }

xiebinJava/ExpandRecycleView

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