<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <ExpandableListView
        android:id="@+id/expandablelistview"
        android:layout_width="match_parent"
        android:layout_height="match_parent">
    </ExpandableListView>

</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/text1"
    android:layout_width="match_parent"
    android:layout_height="45dp"
    android:text="内容"
    android:textSize="15sp"
    android:textColor="@color/fontBlack3"
    android:gravity="center"
    android:background="@color/colorWhite">
</TextView>

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseExpandableListAdapter;
import android.widget.TextView;
import java.util.List;

public class DemoAdapter extends BaseExpandableListAdapter {
    List<String> mGroupList;//一级List
    List<List<String>> mChildList;//二级List 注意!这里是List里面套了一个List<String>,实际项目你可以写一个pojo类来管理2层数据


    public DemoAdapter(List<String> groupList, List<List<String>> childList){
        mGroupList = groupList;
        mChildList = childList;

    }

    @Override
    public int getGroupCount() {//返回第一级List长度
        return mGroupList.size();
    }

    @Override
    public int getChildrenCount(int groupPosition) {//返回指定groupPosition的第二级List长度
        return mChildList.get(groupPosition).size();
    }

    @Override
    public Object getGroup(int groupPosition) {//返回一级List里的内容
        return mGroupList.get(groupPosition);
    }

    @Override
    public Object getChild(int groupPosition, int childPosition) {//返回二级List的内容
        return mChildList.get(groupPosition).get(childPosition);
    }

    @Override
    public long getGroupId(int groupPosition) {//返回一级View的id 保证id唯一
        return groupPosition;
    }

    @Override
    public long getChildId(int groupPosition, int childPosition) {//返回二级View的id 保证id唯一
        return groupPosition + childPosition;
    }

    /**
     * 指示在对基础数据进行更改时子ID和组ID是否稳定
     * @return
     */
    @Override
    public boolean hasStableIds() {
        return true;
    }

    /**
     *  返回一级父View
     */
    @Override
    public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {
        convertView = LayoutInflater.from(parent.getContext()).inflate(R.layout.text_item, parent,false);
        ((TextView)convertView).setText((String)getGroup(groupPosition));
        return convertView;
    }

    /**
     *  返回二级子View
     */
    @Override
    public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
        convertView = LayoutInflater.from(parent.getContext()).inflate(R.layout.text_item, parent,false);
        ((TextView)convertView).setText((String)getChild(groupPosition,childPosition));
        return convertView;
    }

    /**
     *  指定位置的子项是否可选
     */
    @Override
    public boolean isChildSelectable(int groupPosition, int childPosition) {
        return true;
    }
}

        mExpandableListView = findViewById(R.id.expandablelistview);

        List<String> groupList = new ArrayList<>();
        groupList.add("一");
        groupList.add("二");
        groupList.add("三");

        List<List<String>> childList = new ArrayList<>();
        List<String> childList1 = new ArrayList<>();
        childList1.add("1");
        childList1.add("1");
        childList1.add("1");
        List<String> childList2 = new ArrayList<>();
        childList2.add("2");
        childList2.add("2");
        childList2.add("2");
        List<String> childList3 = new ArrayList<>();
        childList3.add("3");
        childList3.add("3");
        childList3.add("3");

        childList.add(childList1);
        childList.add(childList2);
        childList.add(childList3);

        DemoAdapter demoAdapter = new DemoAdapter(groupList, childList);
        mExpandableListView.setAdapter(demoAdapter);

        mExpandableListView.setOnGroupClickListener(new ExpandableListView.OnGroupClickListener() {//一级点击监听
            @Override
            public boolean onGroupClick(ExpandableListView parent, View v, int groupPosition, long id) {

                //如果你处理了并且消费了点击返回true,这是一个基本的防止onTouch事件向下或者向上传递的返回机制
                return false;
            }
        });

        mExpandableListView.setOnChildClickListener(new ExpandableListView.OnChildClickListener() {//二级点击监听
            @Override
            public boolean onChildClick(ExpandableListView parent, View v, int groupPosition, int childPosition, long id) {

                //如果你处理了并且消费了点击返回true
                return false;
            }
        });