android 可展开（收缩）的列表ListView(ExpandableListView)

每天都在用QQ聊天，今天突然一想，android怎么实现列表的分组展开呢？看了看api，发现其实现过程也很简单。先看一下最终效果吧！

1、首先创建我们的Activity，继承 android.app.ExpandableListActivity，直接看代码吧。

package com.ideasandroid.sample;import android.app.ExpandableListActivity;import android.os.Bundle;import com.ideasandroid.sample.adapter.IdeasExpandableListAdapter; /** * @author IdeasAndroid * 可展开（收缩）列表示例 */public class IdeasExpandableListView extends ExpandableListActivity {    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        //设置列表适配器IdeasExpandableListAdapter        setListAdapter(new IdeasExpandableListAdapter(this));    }}

2、创建适配器，继承android.widget.BaseExpandableListAdapter。

package com.ideasandroid.sample.adapter; import java.util.ArrayList;import java.util.List;import android.content.Context;import android.view.Gravity;import android.view.View;import android.view.ViewGroup;import android.widget.AbsListView;import android.widget.BaseExpandableListAdapter;import android.widget.TextView; /** * @author IdeasAndroid  * 可展开（收缩）列表示例 */public class IdeasExpandableListAdapter extends BaseExpandableListAdapter {         private Context mContext = null;        // 测试数据，开发时可能来自数据库，网络....        private String[] groups = { "家人", "朋友", "同事" };        private String[] familis = { "老爸", "老妈", "妹妹" };        private String[] friends = { "小李", "张三", "李四" };        private String[] colleagues = { "陈总", "李工", "李客户" };         private List<String> groupList = null;        private List<List<String>> itemList = null;         public IdeasExpandableListAdapter(Context context) {                this.mContext = context;                groupList = new ArrayList<String>();                itemList = new ArrayList<List<String>>();                initData();        }         /**         * 初始化数据，将相关数据放到List中，方便处理         */        private void initData() {                for (int i = 0; i < groups.length; i++) {                        groupList.add(groups[i]);                }                List<String> item1 = new ArrayList<String>();                for (int i = 0; i < familis.length; i++) {                        item1.add(familis[i]);                }                 List<String> item2 = new ArrayList<String>();                for (int i = 0; i < friends.length; i++) {                        item2.add(friends[i]);                }                 List<String> item3 = new ArrayList<String>();                for (int i = 0; i < colleagues.length; i++) {                        item3.add(colleagues[i]);                }                 itemList.add(item1);                itemList.add(item2);                itemList.add(item3);        }         public boolean areAllItemsEnabled() {                return false;        }         /*         * 设置子节点对象，在事件处理时返回的对象，可存放一些数据         */        public Object getChild(int groupPosition, int childPosition) {                return itemList.get(groupPosition).get(childPosition);        }         public long getChildId(int groupPosition, int childPosition) {                return childPosition;        }         /*         * 字节点视图，这里我们显示一个文本对象         */        public View getChildView(int groupPosition, int childPosition,                        boolean isLastChild, View convertView, ViewGroup parent) {                TextView text = null;                if (convertView == null) {                        text = new TextView(mContext);                } else {                        text = (TextView) convertView;                }                // 获取子节点要显示的名称                String name = (String) itemList.get(groupPosition).get(childPosition);                // 设置文本视图的相关属性                AbsListView.LayoutParams lp = new AbsListView.LayoutParams(                                ViewGroup.LayoutParams.FILL_PARENT, 40);                text.setLayoutParams(lp);                text.setTextSize(18);                text.setGravity(Gravity.CENTER_VERTICAL | Gravity.LEFT);                text.setPadding(45, 0, 0, 0);                text.setText(name);                return text;        }         /*         * 返回当前分组的字节点个数         */        public int getChildrenCount(int groupPosition) {                return itemList.get(groupPosition).size();        }         /*         * 返回分组对象，用于一些数据传递，在事件处理时可直接取得和分组相关的数据         */        public Object getGroup(int groupPosition) {                return groupList.get(groupPosition);        }         /*         * 分组的个数         */        public int getGroupCount() {                return groupList.size();        }         public long getGroupId(int groupPosition) {                return groupPosition;        }         /*         * 分组视图，这里也是一个文本视图         */        public View getGroupView(int groupPosition, boolean isExpanded,                        View convertView, ViewGroup parent) {                TextView text = null;                if (convertView == null) {                        text = new TextView(mContext);                } else {                        text = (TextView) convertView;                }                String name = (String) groupList.get(groupPosition);                AbsListView.LayoutParams lp = new AbsListView.LayoutParams(                                ViewGroup.LayoutParams.FILL_PARENT, 40);                text.setLayoutParams(lp);                text.setTextSize(18);                text.setGravity(Gravity.CENTER_VERTICAL | Gravity.LEFT);                text.setPadding(36, 0, 0, 0);                text.setText(name);                return text;        }         /*         * 判断分组是否为空，本示例中数据是固定的，所以不会为空，我们返回false          * 如果数据来自数据库，网络时，可以把判断逻辑写到这个方法中，如果为空         * 时返回true         */        public boolean isEmpty() {                return false;        }         /*         * 收缩列表时要处理的东西都放这儿         */        public void onGroupCollapsed(int groupPosition) {         }         /*         * 展开列表时要处理的东西都放这儿         */        public void onGroupExpanded(int groupPosition) {         }         /*         * Indicates whether the child and group IDs are stable across changes to         * the underlying data.         */        public boolean hasStableIds() {                return false;        }         /*         * Whether the child at the specified position is selectable.         */        public boolean isChildSelectable(int groupPosition, int childPosition) {                return true;        }}

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