Android二级列表BaseExpandableList

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

public class ListViewAdapter extends BaseExpandableListAdapter {
    private Context context;
    private ArrayList<String> titleList;
    private ArrayList<List<String>> childrenList;

    public ListViewAdapter(
        Context context, ArrayList<String> titleList, 
        ArrayList<List<String>> childrenList)
    {     
        this.context = context;
        this.titleList = titleList;
        this.childrenList = childrenList;
    }

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

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

    @Override
    public Object getGroup(int groupPosition) {
        return titleList.get(groupPosition);
    }

    @Override
    public Object getChild(int groupPosition, int childPosition) {
        return childrenList.get(groupPosition).get(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) {
        //获取文本
        String text = titleList.get(groupPosition);
        if(convertView == null){
            //组列表界面只有一个文本框，直接生成
            convertView = new TextView(context);
            //设定界面，AbsListView:用于实现条目的虚拟列表的基类
            AbsListView.LayoutParams lp = new AbsListView.LayoutParams(
                    ViewGroup.LayoutParams.FILL_PARENT, 60);
            ((TextView) convertView)
            .setGravity(Gravity.CENTER_VERTICAL | Gravity.LEFT); //文本框放在中央
            convertView.setPadding(45, 0, 0, 0);    //设置文本里那个下拉的图标远一点
            convertView.setLayoutParams(lp);
        }
        ((TextView) convertView).setText(text);
        return convertView;
    }

    @Override
    public View getChildView(
        int groupPosition, 
        int childPosition, 
        boolean isLastChild, 
        View convertView, 
        ViewGroup parent) {
        //子列表控件通过界面文件设计
        if(convertView ==null){//convert在运行中会重用，如果不为空，则表明不用重新获取
            LayoutInflater layoutInflater;//使用这个来载入界面
            layoutInflater = LayoutInflater.from(context);
            convertView = layoutInflater.inflate(R.layout.list_item, null);
        }
        TextView tv = (TextView)convertView.findViewById(R.id.text);
        String text = childrenList.get(groupPosition).get(childPosition);
        tv.setText(text);
        //获取文本控件，并设置值
        return convertView;
    }

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

public class MainActivity extends AppCompatActivity {
    private ExpandableListView expandableListView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        expandableListView = (ExpandableListView) findViewById(R.id.list_view);

        ArrayList<String> titleList = new ArrayList<String>();
        ArrayList<List<String>> childrenList = new ArrayList<List<String>>();

        titleList.add("AAA");
        titleList.add("BBB");
        titleList.add("CCC");

        ArrayList<String> cat1 = new ArrayList<String>();
        cat1.add("AAA_1");
        cat1.add("AAA_2");
        cat1.add("AAA_3");
        childrenList.add(cat1);

        ArrayList<String> cat2 = new ArrayList<String>();
        cat2.add("BBB_1");
        cat2.add("BBB_2");
        cat2.add("BBB_3");
        childrenList.add(cat2);

        ArrayList<String> cat3 = new ArrayList<String>();
        cat3.add("CCC_1");
        cat3.add("CCC_2");
        cat3.add("CCC_3");
        childrenList.add(cat3);

        ListViewAdapter listViewAdapter = new ListViewAdapter(
            MainActivity.this, 
            titleList, 
            childrenList);
        expandableListView.setAdapter(listViewAdapter);

        //展开所有组,也可以单独选择某一组展开
        for(int a=0; a<titleList.size(); a++) {
            expandableListView.expandGroup(a);
        }

        expandableListView.setGroupIndicator(null);     //设置组展开标记图,设为null表示没有
        expandableListView.setOnGroupClickListener(new ExpandableListView.OnGroupClickListener() {
            @Override
            public boolean onGroupClick(ExpandableListView parent, View v, int groupPosition, long id) {
                return true;
            }
        });

        //分组项点击事件
        expandableListView.setOnGroupClickListener(new ExpandableListView.OnGroupClickListener() {
            @Override
            public boolean onGroupClick(ExpandableListView parent, View v, int groupPosition, long id) {
                return false;
            }
        });


        //子列表项点击事件
        expandableListView.setOnChildClickListener(new ExpandableListView.OnChildClickListener() {
            @Override
            public boolean onChildClick(ExpandableListView parent, View v, int groupPosition, int childPosition, long id) {
                return false;
            }
        });

    }
}