public class Expandable_test extends Activity {
  private ExpandableListView listView;
  private Map<String, List<String>> dataset = new HashMap<>();
  private String[] parentList = new String[]{"第一個菜單", "第二個菜單"};

  private ExpandableListViewAdpter adpter;
  private Context mContext = this;
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_expandable_test);
    listView=(ExpandableListView)findViewById(R.id.expandableListViewtext);
    adpter=new ExpandableListViewAdpter(this,parentList);
    listView.setAdapter(adpter);
  }

}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:app="http://schemas.android.com/apk/res-auto"
  xmlns:tools="http://schemas.android.com/tools"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  tools:context="com.fae.mobile.testActivity.Expandable_test">
<ExpandableListView
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:id="@+id/expandableListViewtext">

</ExpandableListView>
</LinearLayout>

public class ExpandableListViewAdpter extends BaseExpandableListAdapter {
  private Context mContext;
  private Map<String, List<String>> dataset = new HashMap<>();
  private String[] parentList = new String[]{"第一個菜單", "第二個菜單"};
  private String[][] chdrenList=new String[][]
      {{"菜單1","菜單1","菜單1","菜單1","菜單1","菜單1"},{"菜單2","菜單2","菜單2","菜單2","菜單2"}};

  public ExpandableListViewAdpter(Context context, String[] parentList){
    this.mContext=context;
    this.dataset=dataset;
    this.parentList=parentList;
  }

  @Override
  public int getGroupCount() {
    return parentList.length;
  }

  @Override
  public int getChildrenCount(int groupPosition) {
    return chdrenList[groupPosition].length;
  }

  @Override
  public Object getGroup(int groupPosition) {
    return parentList[groupPosition];
  }

  @Override
  public Object getChild(int groupPosition, int childPosition) {
    return chdrenList[groupPosition][childPosition];
  }

  @Override
  public long getGroupId(int groupPosition) {
    return groupPosition;
  }

  @Override
  public long getChildId(int groupPosition, int childPosition) {
    return childPosition;
  }

  @Override
  public boolean hasStableIds() {
    return true;
  }

  @Override
  public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {
    GroupViewHolder holder=null;
    if(convertView==null){
      convertView = LayoutInflater.from(mContext).inflate(R.layout.itemlayoutexpandable, null);
      holder=new GroupViewHolder();
      holder.text=(TextView)convertView.findViewById(R.id.item_text);
      convertView.setTag(holder);
    }
    else {
      holder=(GroupViewHolder)convertView.getTag();
    }
    holder.text.setText(parentList[groupPosition]);
    return convertView;
  }

  @Override
  public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
    ChildViewHolder holder=null;
      if(convertView==null){
        convertView = LayoutInflater.from(mContext).inflate(R.layout.itemlayoutexpandable, null);
        holder=new ChildViewHolder();
        holder.text=(TextView)convertView.findViewById(R.id.item_text);
        convertView.setTag(holder);
    }
    else {
        holder=(ChildViewHolder)convertView.getTag();
      }
      holder.text.setText(chdrenList[groupPosition][childPosition]);
    return convertView;
  }

  @Override
  public boolean isChildSelectable(int groupPosition, int childPosition) {
    return true;
  }
  class GroupViewHolder {
    TextView text;
  }

  class ChildViewHolder {
    TextView text;
  }
}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="match_parent"
  android:layout_height="match_parent">
<TextView
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:gravity="bottom"
  android:id="@+id/item_text"/>
</LinearLayout>