如何在android中保存可扩展的listview？

// 数据模型类
public class Group {
    private String groupName;
    private List<String> childItems;

    // 构造函数、getter和setter方法

    // ...
}

// 适配器类
public class ExpandableListAdapter extends BaseExpandableListAdapter {
    private List<Group> groups;
    private Context context;

    // 构造函数、重写的方法

    // ...
}

// Activity中的代码
public class MainActivity extends AppCompatActivity {
    private ExpandableListView expandableListView;
    private ExpandableListAdapter expandableListAdapter;
    private List<Group> groups;

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

        // 初始化数据
        groups = new ArrayList<>();
        // 添加组和子项数据

        // 实例化适配器
        expandableListAdapter = new ExpandableListAdapter(groups, this);

        // 实例化ExpandableListView
        expandableListView = findViewById(R.id.expandableListView);
        expandableListView.setAdapter(expandableListAdapter);

        // 添加、删除或修改数据的操作

        // ...

        // 保存数据
        saveData();
    }

    private void saveData() {
        // 使用SharedPreferences或数据库保存数据
        // 示例使用SharedPreferences
        SharedPreferences sharedPreferences = getSharedPreferences("data", MODE_PRIVATE);
        SharedPreferences.Editor editor = sharedPreferences.edit();
        Gson gson = new Gson();
        String json = gson.toJson(groups);
        editor.putString("groups", json);
        editor.apply();
    }

    private void loadData() {
        // 从存储中读取数据
        SharedPreferences sharedPreferences = getSharedPreferences("data", MODE_PRIVATE);
        String json = sharedPreferences.getString("groups", "");
        Gson gson = new Gson();
        groups = gson.fromJson(json, new TypeToken<List<Group>>(){}.getType());
    }
}