Android可收缩伸展的Expandable分组RecyclerView

Android上的可收缩伸展的Expandable RecyclerView第三方开源项目很多，但是在自己的项目引用了这些github上的类似项目后，发现问题和Bug很多，不稳定，无奈之下，自己在RecyclerView基础上写了一个相对稳定、可以收缩伸展Expandable分组RecyclerView。
代码：

import android.graphics.Color; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.support.v7.widget.LinearLayoutManager; import android.support.v7.widget.RecyclerView; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.TextView; import java.util.ArrayList; import java.util.Iterator; public class MainActivity extends AppCompatActivity { private RecyclerViewAdapter mAdapter; private final int GROUP = 0xf01; private final int CHILD = 0xf02; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); RecyclerView mRecyclerView = findViewById(R.id.recycler_view); LinearLayoutManager layoutManager = new LinearLayoutManager(this); layoutManager.setOrientation(LinearLayoutManager.VERTICAL); mRecyclerView.setLayoutManager(layoutManager); ArrayList<Item> mItems = new ArrayList<>(); mAdapter = new RecyclerViewAdapter(mItems); mRecyclerView.setAdapter(mAdapter); String[] groups = {"A", "B", "C", "D", "E", "F"}; for (int i = 0; i < groups.length; i++) { GroupItem groupItem = new GroupItem(); groupItem.id = i; groupItem.title = groups[i]; int count = (int) (Math.random() * 10) % 5 + 1; for (int j = 0; j < count; j++) { ChildItem childItem = new ChildItem(); childItem.id = j; childItem.group = groupItem; groupItem.addChild(childItem); } mAdapter.addGroup(groupItem); } mAdapter.expand(0); } public class RecyclerViewAdapter extends RecyclerView.Adapter<ItemVH> { private ArrayList<Item> items; public RecyclerViewAdapter(ArrayList<Item> items) { this.items = items; } public void addGroup(GroupItem groupItem) { items.add(groupItem); } @Override public ItemVH onCreateViewHolder(ViewGroup parent, int viewType) { View view; ItemVH itemVH = null; switch (viewType) { case GROUP: view = LayoutInflater.from(parent.getContext()).inflate(android.R.layout.simple_list_item_1, parent, false); itemVH = new GroupVH(view); break; case CHILD: view = LayoutInflater.from(parent.getContext()).inflate(android.R.layout.simple_list_item_1, parent, false); itemVH = new ChildVH(view); break; } return itemVH; } @Override public void onBindViewHolder(ItemVH holder, final int position) { int viewType = getItemViewType(position); Item item = items.get(position); switch (viewType) { case GROUP: final GroupItem groupItem = (GroupItem) item; GroupVH groupVH = (GroupVH) holder; groupVH.text1.setText(groupItem.title); groupVH.itemView.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { action(groupItem, position); } }); break; case CHILD: ChildItem childItem = (ChildItem) item; ChildVH childVH = (ChildVH) holder; childVH.text1.setText(childItem.id + ""); break; } } @Override public int getItemCount() { return items.size(); } @Override public int getItemViewType(int position) { return items.get(position).type(); } public void expand(int groupOrder) { for (int i = 0; i < items.size(); i++) { Item item = items.get(i); if (item.type() == GROUP) { GroupItem groupItem = (GroupItem) item; if (groupItem.id == groupOrder) { items.addAll(i + 1, groupItem.children); groupItem.isExpand = true; } } } mAdapter.notifyDataSetChanged(); } private void action(GroupItem groupItem, int position) { groupItem.isExpand = !groupItem.isExpand; if (groupItem.isExpand) { items.addAll(position + 1, groupItem.children); } else { Iterator<Item> iterator = items.iterator(); while (iterator.hasNext()) { Item it = iterator.next(); if (it.type() == CHILD) { ChildItem cid = (ChildItem) it; if (cid.group.id == groupItem.id) iterator.remove(); } } } mAdapter.notifyDataSetChanged(); } } private abstract class Item { public int id; public abstract int type(); } private abstract class ItemVH extends RecyclerView.ViewHolder { public ItemVH(View itemView) { super(itemView); } public abstract int type(); } private class ChildItem extends Item { public GroupItem group; @Override public int type() { return CHILD; } } private class GroupItem extends Item { public String title; public boolean isExpand = false; public ArrayList<ChildItem> children; public GroupItem() { children = new ArrayList<>(); } @Override public int type() { return GROUP; } public void addChild(ChildItem childItem) { children.add(childItem); } } private class ChildVH extends ItemVH { public TextView text1; public ChildVH(View itemView) { super(itemView); text1 = itemView.findViewById(android.R.id.text1); text1.setBackgroundColor(Color.LTGRAY); } @Override public int type() { return CHILD; } } private class GroupVH extends ItemVH { private TextView text1; public GroupVH(View itemView) { super(itemView); text1 = itemView.findViewById(android.R.id.text1); text1.setTextColor(Color.WHITE); itemView.setBackgroundColor(Color.RED); } @Override public int type() { return GROUP; } } } 

运行结果：

启动后首先为用户伸展开第0组（即第一组）。在以上代码基础上，有兴趣的读者可以再次深度二次定制化开发，比如在group的组GroupVH上增加收缩伸展改变时候的指示箭头。