<?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"
  tools:context="com.studying.expandablelistviewdemo.MainActivity">

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

</LinearLayout>

public class MainActivity extends Activity {

  private ExpandableListView elv;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    elv = (ExpandableListView) findViewById(R.id.elv_local_data);
    MyBaseExpandableListAdapter adapter = new MyBaseExpandableListAdapter(this, LoadData.getGroupData(), LoadData.getChildData());
    elv.setAdapter(adapter);
  }
}

public class LoadData {

  // 组的数据内容
  public static List<String> getGroupData() {
    List<String> groupDataList = new ArrayList<>();
    groupDataList.add("计算机基础");
    groupDataList.add("安卓开发");
    return groupDataList;
  }

  // 子条目的数据内容
  public static List<List<String>> getChildData() {
    List<List<String>> childDataList = new ArrayList<>();

    List<String> group1 = new ArrayList<>();
    group1.add("数据结构");
    group1.add("算法");
    group1.add("计算机网络");
    childDataList.add(group1);

    List<String> group2 = new ArrayList<>();
    group2.add("控件使用");
    group2.add("网络操作");
    group2.add("数据存储");
    group2.add("四大组件");
    childDataList.add(group2);

    return childDataList;
  }
}

public class MyBaseExpandableListAdapter extends BaseExpandableListAdapter {

  private Context mContext;

  private List<String> groupName;
  private List<List<String>> childName;

  public MyBaseExpandableListAdapter(Context mContext, List<String> groupName, List<List<String>> childName) {
    this.mContext = mContext;
    this.groupName = groupName;
    this.childName = childName;
  }

  @Override
  public int getGroupCount() {
    return groupName.size();
  }

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

  @Override
  public String getGroup(int groupPosition) {
    return groupName.get(groupPosition);
  }

  @Override
  public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {
  
    convertView = View.inflate(mContext, R.layout.item_group_name, null);

    TextView groupName = (TextView) convertView.findViewById(R.id.group_name);
    groupName.setText(getGroup(groupPosition));

    return convertView;
  }

  @Override
  public int getChildrenCount(int groupPosition) {
    return childName.get(groupPosition).size();
  }

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

  @Override
  public String getChild(int groupPosition, int childPosition) {
    return childName.get(groupPosition).get(childPosition);
  }

  @Override
  public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
  
    convertView = View.inflate(mContext, R.layout.item_child_name, null);

    TextView childName = (TextView) convertView.findViewById(R.id.child_name);
    childName.setText(getChild(groupPosition, childPosition));

    return convertView;
  }

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

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