由于工作需要，今天简单研究了一下ExpandableListView，做了一个类似QQ列表的Demo，和大家分享一下。
效果图如下：
先来看看主布局文件：
<RelativeLayout xmlns:android="/apk/res/android"xmlns:tools="/tools"android:layout_width="match_parent"android:layout_height="match_parent"android:background="#EDEDED"tools:context="com.example.expandablelistview.MainActivity" ><ExpandableListView android:id="@+id/my_listview"android:layout_width="match_parent"android:layout_height="match_parent"android:layout_marginLeft="8dp"android:layout_marginRight="8dp"android:layout_marginTop="10dp"android:divider="@null"android:dividerHeight="8dip" ></ExpandableListView></RelativeLayout>
这里我们不使用系统默认的分隔线，两个组之间的距离为8dp.
对于ExpandableListView，系统为我们提供了专门的适配器BaseExpandableListAdapter，我们可以自定义一个适配器继承BaseExpandableListAdapter，实现该类中的一些方法即可。
代码如下：
public class MyAdapter extends BaseExpandableListAdapter {private List<GroupBean> list;private Context context;public MyAdapter(List<GroupBean> list, Context context) {this.list = list;this.context = context;}public MyAdapter() {}@Overridepublic int getGroupCount() {return list.size();}@Overridepublic int getChildrenCount(int groupPosition) {return list.get(groupPosition).getChildren().size();}@Overridepublic Object getGroup(int groupPosition) {return list.get(groupPosition);}@Overridepublic Object getChild(int groupPosition, int childPosition) {return list.get(groupPosition).getChildren().get(childPosition);}@Overridepublic long getGroupId(int groupPosition) {return groupPosition;}@Overridepublic long getChildId(int groupPosition, int childPosition) {return childPosition;}@Overridepublic boolean hasStableIds() {return false;}@Overridepublic View getGroupView(int groupPosition, boolean isExpanded,View convertView, ViewGroup parent) {GroupHolder holder;if (convertView == null) {holder = new GroupHolder();convertView = LayoutInflater.from(context).inflate(R.layout.item_group, null);holder.title = (TextView) convertView.findViewById(R.id.group_title);holder.iv = (ImageView) convertView.findViewById(R.id.group_ico);convertView.setTag(holder);} else {holder = (GroupHolder) convertView.getTag();}holder.title.setText(list.get(groupPosition).getGroupName());if (isExpanded) {holder.iv.setImageResource(R.drawable.rounds_open);} else {holder.iv.setImageResource(R.drawable.rounds_close);}return convertView;}@Overridepublic View getChildView(int groupPosition, int childPosition,boolean isLastChild, View convertView, ViewGroup parent) {ChildHolder holder;if (convertView == null) {holder = new ChildHolder();convertView = LayoutInflater.from(context).inflate(R.layout.item_child, null);holder.name = (TextView) convertView.findViewById(R.id.child_name);holder.sign = (TextView) convertView.findViewById(R.id.child_sign);convertView.setTag(holder);} else {holder = (ChildHolder) convertView.getTag();}ChildBean cb = list.get(groupPosition).getChildren().get(childPosition);holder.name.setText(cb.getName());holder.sign.setText("[签名]"+cb.getSign());return convertView;}@Overridepublic boolean isChildSelectable(int groupPosition, int childPosition) {return false;}class GroupHolder {TextView title;ImageView iv;}class ChildHolder {TextView name, sign;}}
这里的代码有点长，我们稍微解释一下，先是构造方法中传入两个参数，一个是数据源list，另外一个是上下文，list是一个GroupBean集合，GroupBean如下：
public class GroupBean {private String groupName;private List<ChildBean> children;public String getGroupName() {return groupName;}public void setGroupName(String groupName) {this.groupName = groupName;}public List<ChildBean> getChildren() {return children;}public void setChildren(List<ChildBean> children) {this.children = children;}public GroupBean(String groupName, List<ChildBean> children) {this.groupName = groupName;this.children = children;}public GroupBean() {}}
很明显，GroupBean有两个属性，一个是组名字，另外一个是该组下子项的一个集合，这个ChildBean就是每个组下面的每一个对象的数据，ChildBean代码如下：
public class ChildBean {private String name;private String sign;public String getName() {return name;}public void setName(String name) {this.name = name;}public String getSign() {return sign;}public void setSign(String sign) {this.sign = sign;}public ChildBean(String name, String sign) {this.name = name;this.sign = sign;}public ChildBean() {}}
说完list，下面就是getGroupCount()和getChildrenCount(),这个有点类似于我们使用BaseAdapter时的getCount(),不同的是这里分别要返回每个组的数量，以及组内成员的数量，那么组的数量当然就是list.size()，组内成员的数量由于每组不同，所以要先拿到每个组，再拿到该组里成员的数量，代码就是list.get(groupPosition).getChildren().size();。接下来的两个方法就是getGroup()和getChild(),这个类似于BaseAdapter中的getItem，我们返回的时候还是组和组内的子项分开返回，代码很简单，就不多说了。稍微长一点的方法就是getGroupView和getChildView，不多也都没啥逻辑，和我们在ListView中使用BaseAdapter中的getView方法差不多，不同的是数据赋值的时候有差别。
我个人觉得，使用ExpandableListView关键在于把数据结构搞清楚，Group和Child搞清楚了，其他的都很简单。
这里我把Group的布局和Child的布局贴出来给大家看看：
item_group.xml
<?xml version="1.0" encoding="utf-8"?><RelativeLayout xmlns:android="/apk/res/android"android:layout_width="match_parent"android:layout_height="48dp"android:background="@drawable/item_background_select" ><TextView android:id="@+id/group_title"android:layout_width="wrap_content"android:layout_height="48dp"android:layout_marginLeft="36dp"android:gravity="center"android:text="好友分组"android:textSize="18sp" /><ImageView android:id="@+id/group_ico"android:layout_width="24dip"android:layout_height="24dip"android:layout_alignParentRight="true"android:layout_marginBottom="12dp"android:layout_marginLeft="24dp"android:layout_marginRight="24dp"android:layout_marginTop="12dp"android:scaleType="centerInside"android:src="@drawable/rounds_close" /><TextView android:id="@+id/split_lines"android:layout_width="1dip"android:layout_height="48dp"android:layout_toLeftOf="@id/group_ico"android:background="#E6E6E6" /></RelativeLayout>
item_child.xml
<?xml version="1.0" encoding="utf-8"?><RelativeLayout xmlns:android="/apk/res/android"android:layout_width="match_parent"android:layout_height="36dp"android:orientation="vertical" ><TextView android:id="@+id/child_name"android:layout_width="match_parent"android:layout_height="wrap_content"android:paddingLeft="10dip"android:text="姓名"android:textSize="18sp" /><TextView android:id="@+id/child_sign"android:layout_width="match_parent"android:layout_height="wrap_content"android:layout_below="@id/child_name"android:paddingLeft="10dip"android:paddingRight="10dip"android:text="签名"android:textSize="12sp" /><View android:layout_width="match_parent"android:layout_height="1dp"android:background="#B2DFEE" /></RelativeLayout>
这里还涉及到一个圆角方框，代码是这样的：
item_background_select.xml
<?xml version="1.0" encoding="utf-8"?><shape xmlns:android="/apk/res/android" ><corners android:radius="8dip" /><solid android:color="#FFFFFFFF" /></shape>
好了，所有的准备工作都已经完成，下面看看怎么使用
public class MainActivity extends Activity {private ExpandableListView mListView;private MyAdapter adapter;private List<GroupBean> list;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);//初始化数据initData();mListView = (ExpandableListView) this.findViewById(R.id.my_listview);adapter = new MyAdapter(list, this);mListView.setAdapter(adapter);mListView.setGroupIndicator(null);//mListView.expandGroup(0);}private void initData() {list = new ArrayList<GroupBean>();{List<ChildBean> list1 = new ArrayList<ChildBean>();ChildBean cb1 = new ChildBean("妈妈", "123");ChildBean cb2 = new ChildBean("爸爸", "456");ChildBean cb3 = new ChildBean("爷爷", "789");ChildBean cb4 = new ChildBean("妹妹", "000");list1.add(cb1);list1.add(cb2);list1.add(cb3);list1.add(cb4);GroupBean gb1 = new GroupBean("家", list1);list.add(gb1);}{List<ChildBean> list1 = new ArrayList<ChildBean>();ChildBean cb1 = new ChildBean("张三", "123");ChildBean cb2 = new ChildBean("李四", "456");ChildBean cb3 = new ChildBean("王五", "789");ChildBean cb4 = new ChildBean("赵六", "000");ChildBean cb5 = new ChildBean("风起", "1111");ChildBean cb6 = new ChildBean("马坝", "222");ChildBean cb7 = new ChildBean("迁就", "3333333");list1.add(cb1);list1.add(cb2);list1.add(cb3);list1.add(cb4);list1.add(cb5);list1.add(cb6);list1.add(cb7);GroupBean gb1 = new GroupBean("我的朋友", list1);list.add(gb1);}{List<ChildBean> list1 = new ArrayList<ChildBean>();ChildBean cb1 = new ChildBean("Tom", "123");ChildBean cb2 = new ChildBean("Jerry", "456");ChildBean cb4 = new ChildBean("Bush", "000");list1.add(cb1);list1.add(cb2);list1.add(cb4);GroupBean gb1 = new GroupBean("国际友人", list1);list.add(gb1);}{List<ChildBean> list1 = new ArrayList<ChildBean>();ChildBean cb1 = new ChildBean("赵工", "123");ChildBean cb2 = new ChildBean("马工", "456");ChildBean cb3 = new ChildBean("王工", "789");ChildBean cb4 = new ChildBean("李工", "000");ChildBean cb5 = new ChildBean("为工", "000");list1.add(cb1);list1.add(cb2);list1.add(cb3);list1.add(cb4);list1.add(cb5);GroupBean gb1 = new GroupBean("同事", list1);list.add(gb1);}}}
这里有两行代码我稍微说一下mListView.setGroupIndicator(null);表示不使用系统提供的展开和收起的图标，mListView.expandGroup(0);表示默认打开第一项。
好了，就说这些，有问题欢迎留言讨论。
本文源码下载地址/lenve/expandablelistviewtest1
