Android Mulitilevel listview或expandble listview

Question

我使用多级ExpandableListView，如何达到3级Listview请给出一些参考。

我添加了2个级别，但无法在第2级ExpandableListView子元素中添加第3级子元素。

public class MainActivity extends Activity implements OnClickListener
{

    private LinkedHashMap<String, Header> myDepartments = new LinkedHashMap<String, Header>();
    private ArrayList<Header> deptList = new ArrayList<Header>();

    private ListAdapter listAdapter;
    private ExpandableListView myList;
    List<String> li;
    EditText et;
    Spinner spinner;

    @Override

    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        spinner = (Spinner) findViewById(R.id.department);
        li=new ArrayList<String>();
        Button b=(Button) findViewById(R.id.add1);
        et=(EditText)findViewById(R.id.product1);
        b.setOnClickListener(new View.OnClickListener()
        {
           public void onClick(View v)
           {
                // TODO Auto-generated method stub

                li.add(et.getText().toString());
                et.setText(null);
                add();
            }
        });

        add();



        myList = (ExpandableListView) findViewById(R.id.myList);
        listAdapter = new ListAdapter(MainActivity.this, deptList);
        myList.setAdapter(listAdapter);
        expandAll();
        Button add = (Button) findViewById(R.id.add);
        add.setOnClickListener(this);
        myList.setOnChildClickListener(myListItemClicked);
        myList.setOnGroupClickListener(myListGroupClicked);
    }

    private void add()
    {
        ArrayAdapter<String> adp=new ArrayAdapter<String>(this,
                android.R.layout.simple_dropdown_item_1line,li);
        spinner.setAdapter(adp);
    }


    public void onClick(View v)
    {

        switch (v.getId())
        {

            //add entry to the List
            case R.id.add:

                Spinner spinner = (Spinner) findViewById(R.id.department);
                String department = spinner.getSelectedItem().toString();
                EditText editText = (EditText) findViewById(R.id.product);
                String product = editText.getText().toString();
                editText.setText("");
                int groupPosition = addProduct(department,product);
                listAdapter.notifyDataSetChanged();
                collapseAll();
                myList.expandGroup(groupPosition);
                myList.setSelectedGroup(groupPosition);
              break;

        }
    }


    //method to expand all groups
    private void expandAll() {
        int count = listAdapter.getGroupCount();
        for (int i = 0; i < count; i++){
            myList.expandGroup(i);
        }
    }

    //method to collapse all groups
    private void collapseAll() {
        int count = listAdapter.getGroupCount();
        for (int i = 0; i < count; i++){
            myList.collapseGroup(i);
        }
    }


    //our child listener
    private OnChildClickListener myListItemClicked =  new OnChildClickListener() {

        public boolean onChildClick(ExpandableListView parent, View v,
                                    int groupPosition, int childPosition, long id) {

            //get the group header
            Header headerInfo = deptList.get(groupPosition);
            //get the child info
            Detail detailInfo =  headerInfo.getProductList().get(childPosition);
            //display it or do something with it
            Toast.makeText(getBaseContext(), "Clicked on Detail " + headerInfo.getName()
                    + "/" + detailInfo.getName(), Toast.LENGTH_LONG).show();
            return false;
        }

    };

    //our group listener
    private OnGroupClickListener myListGroupClicked =  new OnGroupClickListener()
    {

        public boolean onGroupClick(ExpandableListView parent, View v,
                                    int groupPosition, long id) {

            //get the group header
            Header headerInfo = deptList.get(groupPosition);
            //display it or do something with it
            Toast.makeText(getBaseContext(), "Child on Header " + headerInfo.getName(),
                    Toast.LENGTH_LONG).show();

            return false;
        }

    };

    private int addProduct(String department, String product){

        int groupPosition = 0;

        //check the hash map if the group already exists
        Header headerInfo = myDepartments.get(department);
        //add the group if doesn't exists
        if(headerInfo == null){
            headerInfo = new Header();
            headerInfo.setName(department);
            myDepartments.put(department, headerInfo);
            deptList.add(headerInfo);
        }

        //get the children for the group
        ArrayList<Detail> productList = headerInfo.getProductList();
        //size of the children list
        int listSize = productList.size();
        //add to the counter
        listSize++;

        //create a new child and add that to the group
        Detail detailInfo = new Detail();
        detailInfo.setSequence(String.valueOf(listSize));
        detailInfo.setName(product);
        productList.add(detailInfo);
        headerInfo.setProductList(productList);

        //find the group position inside the list
        groupPosition = deptList.indexOf(headerInfo);
        return groupPosition;
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }
}