在某些android开发群里，看到有些新手问怎么实现QQ好友列表，其实网上一搜挺多的。接触Android，也才一年的时间，大部分时间花在工作上（解bug。。。），界面上开发很少参与。自己维护的系统应用里，有个ExpandableListView的界面（其实android例子APIDemo也有类似的例子）就在这里写个Demo供新手参考。
ExpandableListView的用法：难点就是重写BaseExpandableListAdapter及提供的数据源。
下面看看继承BaseExpandableListAdapter的适配器：
[java]
<span xmlns="http://www.w3.org/1999/xhtml" style="">package com.xyz.expande;
import java.util.List;
import android.app.AlertDialog;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseExpandableListAdapter;
import android.widget.ImageView;
import android.widget.TextView;
public class ExpandAdapter extends BaseExpandableListAdapter {
private Context mContext;
private LayoutInflater mInflater = null;
private String[]mGroupStrings = null;
private List<List<Item>>mData = null;
public ExpandAdapter(Context ctx, List<List<Item>> list) {
mContext = ctx;
mInflater = (LayoutInflater) mContext
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
mGroupStrings = mContext.getResources().getStringArray(R.array.groups);
mData = list;
}
public void setData(List<List<Item>> list) {
mData = list;
}
@Override
public int getGroupCount() {
// TODO Auto-generated method stub
return mData.size();
}
@Override
public int getChildrenCount(int groupPosition) {
// TODO Auto-generated method stub
return mData.get(groupPosition).size();
}
@Override
public List<Item> getGroup(int groupPosition) {
// TODO Auto-generated method stub
return mData.get(groupPosition);
}
@Override
public Item getChild(int groupPosition, int childPosition) {
// TODO Auto-generated method stub
return mData.get(groupPosition).get(childPosition);
}
@Override
public long getGroupId(int groupPosition) {
// TODO Auto-generated method stub
return groupPosition;
}
@Override
public long getChildId(int groupPosition, int childPosition) {
// TODO Auto-generated method stub
return childPosition;
}
@Override
public boolean hasStableIds() {
// TODO Auto-generated method stub
return false;
}
@Override
public View getGroupView(int groupPosition, boolean isExpanded,
View convertView, ViewGroup parent) {
// TODO Auto-generated method stub
if (convertView == null) {
convertView = mInflater.inflate(R.layout.group_item_layout, null);
}
GroupViewHolder holder = new GroupViewHolder();
holder.mGroupName = (TextView) convertView
.findViewById(R.id.group_name);
holder.mGroupName.setText(mGroupStrings[groupPosition]);
holder.mGroupCount = (TextView) convertView
.findViewById(R.id.group_count);
holder.mGroupCount.setText("[" + mData.get(groupPosition).size() + "]");
return convertView;
}
@Override
public View getChildView(int groupPosition, int childPosition,
boolean isLastChild, View convertView, ViewGroup parent) {
// TODO Auto-generated method stub
if (convertView == null) {
convertView = mInflater.inflate(R.layout.child_item_layout, null);
}
ChildViewHolder holder = new ChildViewHolder();
holder.mIcon = (ImageView) convertView.findViewById(R.id.img);
holder.mIcon.setBackgroundResource(getChild(groupPosition,
childPosition).getImageId());
holder.mChildName = (TextView) convertView.findViewById(R.id.item_name);
holder.mChildName.setText(getChild(groupPosition, childPosition)
.getName());
holder.mDetail = (TextView) convertView.findViewById(R.id.item_detail);
holder.mDetail.setText(getChild(groupPosition, childPosition)
.getDetail());
return convertView;
}
@Override
public boolean isChildSelectable(int groupPosition, int childPosition) {
// TODO Auto-generated method stub
<span style="color:#cc0000;">/*很重要：实现ChildView点击事件，必须返回true*/
</span>return true;
}
private class GroupViewHolder {
TextView mGroupName;
TextView mGroupCount;
}
private class ChildViewHolder {
ImageView mIcon;
TextView mChildName;
TextView mDetail;
}
}
</span>
里面用到的有两个布局，GroupView（子list没展开的view）如图：
布局group_item_layout.xml如下:
[java]
<span xmlns="http://www.w3.org/1999/xhtml" style=""><span xmlns="http://www.w3.org/1999/xhtml" style=""><?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="?android:attr/listPreferredItemHeight"
android:orientation="horizontal" >
<TextView
android:id="@+id/group_name"
android:layout_width="wrap_content"
android:layout_height="?android:attr/listPreferredItemHeight"
android:textAppearance="?android:attr/textAppearanceMedium"
android:layout_marginLeft="35dip"
android:gravity="center_vertical"
android:singleLine="true" />
<TextView
android:id="@+id/group_count"
android:layout_width="wrap_content"
android:layout_height="?android:attr/listPreferredItemHeight"
android:textAppearance="?android:attr/textAppearanceMedium"
android:layout_marginLeft="5dip"
android:gravity="center_vertical"
android:singleLine="true"/>
</LinearLayout></span></span>
另外一个就是ChildView，本例仿QQ好友列表，如图：
哈哈，熟悉吧。布局child_item_layout.xml如下：
[java]
<span xmlns="http://www.w3.org/1999/xhtml" style=""><span xmlns="http://www.w3.org/1999/xhtml" style=""><?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:minHeight="@dimen/min_Height"
<span style="color:#ff0000;">android:descendantFocusability="blocksDescendants"
</span>android:orientation="horizontal" >
<ImageButton
android:id="@+id/img"
android:layout_width="@dimen/image_width"
android:layout_height="@dimen/image_width"
android:layout_marginLeft="2dip"
android:layout_marginRight="10dip"
android:layout_gravity="center_vertical" />
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:descendantFocusability="blocksDescendants"
android:orientation="vertical" >
<TextView
android:id="@+id/item_name"
android:layout_width="wrap_content"
android:layout_height="0.0dip"
android:gravity="center_vertical"
android:layout_weight="1" />
<TextView
android:id="@+id/item_detail"
android:layout_width="wrap_content"
android:layout_height="0.0dip"
android:gravity="center_vertical"
android:singleLine="true"
android:ellipsize="end"
android:layout_weight="1" />
</LinearLayout>
</LinearLayout></span></span>
适配器弄好了，ExpandableListView就用系统的，现在只剩下显示的问题啦
先来几张效果图：
主Activity如下：
onChildClick
[java]
<span xmlns="http://www.w3.org/1999/xhtml" style=""><span xmlns="http://www.w3.org/1999/xhtml" style="">package com.xyz.expande;
import java.util.ArrayList;
import java.util.List;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.DialogInterface.OnClickListener;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup.LayoutParams;
import android.widget.ExpandableListView;
import android.widget.ExpandableListView.OnChildClickListener;
public class HomeActivity extends Activity implements OnChildClickListener {
private ExpandableListView mListView = null;
private ExpandAdapter mAdapter = null;
private List<List<Item>> mData = new ArrayList<List<Item>>();
private int[] mGroupArrays = new int[] {
R.array.tianlongbabu,
R.array.shediaoyingxiongzhuan,
R.array.shendiaoxialv };
private int[] mDetailIds = new int[] {
R.array.tianlongbabu_detail,
R.array.shediaoyingxiongzhuan_detail,
R.array.shendiaoxialv_detail };
private int[][] mImageIds = new int[][] {
{ R.drawable.img_00,
R.drawable.img_01,
R.drawable.img_02 },
{ R.drawable.img_10,
R.drawable.img_11,
R.drawable.img_12,
R.drawable.img_13,
R.drawable.img_14,
R.drawable.img_15,
R.drawable.img_16 },
{ R.drawable.img_20,
R.drawable.img_21 } };
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
initData();
mListView = new ExpandableListView(this);
mListView.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT,
LayoutParams.FILL_PARENT));
setContentView(mListView);
mListView.setGroupIndicator(getResources().getDrawable(
R.drawable.expander_floder));
mAdapter = new ExpandAdapter(this, mData);
mListView.setAdapter(mAdapter);
mListView
.setDescendantFocusability(ExpandableListView.FOCUS_AFTER_DESCENDANTS);
mListView.setOnChildClickListener(this);
}
<span style="color:#ff0000;">/*
* ChildView 设置 布局很可能onChildClick进不来，要在 ChildView layout 里加上
* android:descendantFocusability="blocksDescendants",
* 还有isChildSelectable里返回true
*/
</span>@Override
public boolean onChildClick(ExpandableListView parent, View v,
int groupPosition, int childPosition, long id) {
// TODO Auto-generated method stub
Item item = mAdapter.getChild(groupPosition, childPosition);
new AlertDialog.Builder(this)
.setTitle(item.getName())
.setMessage(item.getDetail())
.setIcon(android.R.drawable.ic_menu_more)
.setNegativeButton(android.R.string.cancel,
new OnClickListener() {
@Override
public void onClick(DialogInterface dialog,
int which) {
// TODO Auto-generated method stub
}
}).create().show();
return true;
}
private void initData() {
for (int i = 0; i < mGroupArrays.length; i++) {
List<Item> list = new ArrayList<Item>();
String[] childs = getStringArray(mGroupArrays[i]);
String[] details = getStringArray(mDetailIds[i]);
for (int j = 0; j < childs.length; j++) {
Item item = new Item(mImageIds[i][j], childs[j], details[j]);
list.add(item);
}
mData.add(list);
}
}
private String[] getStringArray(int resId) {
return getResources().getStringArray(resId);
}
}</span></span>
这这个demo的时候，想实现ChildView的点击事件，实现接口onChildClick，发现不进来，很尴尬。。。最后还是在网上找到答案了，第一，在适配器里isChildSelectable 必须返回true，第二，ChildView布局child_item_layout.xml最外层的layout设置个属性：
[java]
<span xmlns="http://www.w3.org/1999/xhtml" style=""><span xmlns="http://www.w3.org/1999/xhtml" style=""><span xmlns="http://www.w3.org/1999/xhtml" style=""><span xmlns="http://www.w3.org/1999/xhtml" style="">android:descendantFocusability="blocksDescendants"</span></span></span></span>
上面已标示红色的啦。
细心的同学会发现 Item 是啥？也贴出来吧
[java]
package com.xyz.expande;
public class Item {
private int resId;
private String name;
private String detail;
public Item(int resId, String name, String detail) {
this.resId= resId;
this.name= name;
this.detail = detail;
}
public void setImageId(int resId) {
this.resId= resId;
}
public int getImageId() {
return resId;
}
public void setName(String name) {
this.name= name;
}
public String getName() {
return name;
}
public void setDetail(String detail) {
this.detail = detail;
}
public String getDetail() {
return detail;
}
public String toString() {
return "Item[" + resId + ", " + name + ", " + detail + "]";
}
}
。。。这不是面向对象程序设计（OOP)类及类的实现最简单的例子么。
谢谢观看，有不对的地方请指正，互相学习！
