ExpandableListView-可展开的列表组件

ExpandableListView （可展开的列表）组件，用于实现列表的分组显示，点击组item可弹出子item。
ExpandableListView的使用举例：
(1)在Activity的布局文件（activity_main.xml）中定义ExpandableListView:

<RelativeLayout 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" android:paddingBottom="@dimen/activity_vertical_margin" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" tools:context="com.example.android_expandable_listview.MainActivity" >

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

</RelativeLayout>

(2)定义ExpandableListView的组元素布局（expandable_listview_child_item.xml）和子元素（expandable_listview_child_item.xml）布局。
组元素布局：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" >
    <TextView  android:id="@+id/group_title" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginLeft="20dip" android:textSize="20sp" >
    </TextView>
</RelativeLayout>

子元素布局：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" >
    <TextView  android:id="@+id/child_title" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentLeft="true" android:layout_marginLeft="15dip" android:textSize="15sp" >
    </TextView>
</RelativeLayout>

(3)Activity中的代码：

public class MainActivity extends Activity {
    ExpandableListView listview;
    List<String> groupData = new ArrayList<String>(); // 组数据
    List<List<String>> childData = new ArrayList<List<String>>(); // 子元素数据
    MyExpandableListAdapter adapter;

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

    /** * 初始化数据 */
    public void initData() {
        /* * 初始化组数据 */
        groupData.add("数学");
        groupData.add("计算机");
        groupData.add("语言");
        List<String> child1 = new ArrayList<String>();
        child1.add("线性代数");
        child1.add("解析几何");
        child1.add("概率统计");

        List<String> child2 = new ArrayList<String>();
        child2.add("数据结构");
        child2.add("C语言");
        child2.add("Java程序设计");

        List<String> child3 = new ArrayList<String>();
        child3.add("英语");
        child3.add("日语");
        child3.add("俄语");

        childData.add(child1);
        childData.add(child2);
        childData.add(child3);
    }

    /** * 初始化视图 */
    public void initView() {
        listview = (ExpandableListView) findViewById(R.id.listview);
        adapter = new MyExpandableListAdapter(this, groupData, childData);
        listview.setAdapter(adapter);
    }

    public class MyExpandableListAdapter extends BaseExpandableListAdapter {
        List<String> groupData;
        List<List<String>> childData;
        Context context;

        public MyExpandableListAdapter(Context context, List<String> groupData, List<List<String>> childData) {
            // TODO Auto-generated constructor stub
            this.context = context;
            this.groupData = groupData;
            this.childData = childData;
        }

        @Override
        public Object getChild(int groupPosition, int childPosition) {
            // TODO Auto-generated method stub

            return childData.get(groupPosition).get(childPosition);
        }

        @Override
        public long getChildId(int groupPosition, int childPosition) {
            // TODO Auto-generated method stub
            return childPosition;
        }

        @Override
        public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView,
                ViewGroup parent) {
            // TODO Auto-generated method stub
            ChildViewHolder childViewHolder = new ChildViewHolder();
            if (convertView == null) {
                convertView = LayoutInflater.from(context).inflate(R.layout.expandable_listview_child_item, parent,
                        false);
                childViewHolder.childTitle = (TextView) convertView.findViewById(R.id.child_title);
                convertView.setTag(childViewHolder);
            } else {
                childViewHolder = (ChildViewHolder) convertView.getTag();
            }
            childViewHolder.childTitle.setText(childData.get(groupPosition).get(childPosition));
            return convertView;
        }

        @Override
        public int getChildrenCount(int groupPosition) {
            // TODO Auto-generated method stub
            return childData.get(groupPosition).size();
        }

        @Override
        public Object getGroup(int groupPosition) {
            // TODO Auto-generated method stub
            return groupData.get(groupPosition);
        }

        @Override
        public int getGroupCount() {
            // TODO Auto-generated method stub
            return groupData.size();
        }


        @Override
        public long getGroupId(int groupPosition) {
            // TODO Auto-generated method stub
            return groupPosition;
        }

        @Override
        public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {
            // TODO Auto-generated method stub
            GroupViewHolder groupViewHolder = new GroupViewHolder();
            if (convertView == null) {
                convertView = LayoutInflater.from(context).inflate(R.layout.expandable_listview_group_item, parent,
                        false);
                groupViewHolder.groupTitle = (TextView) convertView.findViewById(R.id.group_title);
                convertView.setTag(groupViewHolder);
            } else {
                groupViewHolder = (GroupViewHolder) convertView.getTag();
            }
            groupViewHolder.groupTitle.setText(groupData.get(groupPosition));
            return convertView;
        }

        @Override
        public boolean hasStableIds() {
            // TODO Auto-generated method stub
            return true;
        }

        @Override
        public boolean isChildSelectable(int groupPosition, int childPosition) {
            // TODO Auto-generated method stub
            return true;
        }

        class ChildViewHolder {
            TextView childTitle;
        }

        class GroupViewHolder {
            TextView groupTitle;
        }
    }
}