Android上 ExpandableListActivity及CursorTreeAdapter的使用简介

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ExpandableListeActivity顾名思义是ListActivity的一种，但与ListActivy不同的是，ExpandableListeActivity的展示效果是有可以呈现多级目录的ExpandableListView。下面我简单介绍一下如何使用ExpandableListeActivity。

首先，我们在想要实现的Activity继承ExpandableListeActivity如下：

public classGroupListActivity extends ExpandableListActivity

在这个布局中我们用到了布局文件setContentView(R.layout.group_list)中的group_list.xml。让我们来看看group_list里都有什么

<RelativeLayoutxmlns:android=http://schemas.android.com/apk/res/android

android:layout_width="fill_parent"android:layout_height="fill_parent"

android:orientation="vertical">

<ExpandableListViewandroid:layout_width="fill_parent"

android:layout_height="wrap_content"android:id="@android:id/list"

android:layout_alignParentTop="true"></ExpandableListView>

</RelativeLayout>

可见，与ListActivity类似，我们在使用ExpandableListView的布局文件里必须声明一个ExpandableListView的控件，其ID为list。这样我们在自己的Activity里才能找到这个ExpandableListview。与ExpandableListview对应的Adapter有几种。在此我们只介绍CursorTreeAdapter，因为这个属于不是很常用的Adapter，国内的介绍也很少。CursorTreeAdapter是BaseExpandableListAdapter的一个子类。其实现代码如下：

public class GroupListAdapter extends CursorTreeAdapter {

private GroupViewCachecache;

private ChildViewCachechildCache;

public static final int LoadHead = 100;

private DrawabledefaultDrawable;

private GroupListPhotoCachephotoCache;

private Contextctx;

public GroupListAdapter(Cursor cursor, Context context,boolean autoRequery) {

super(cursor, context, autoRequery);

// TODO Auto-generatedconstructor stub

this.photoCache = GroupListPhotoCache.getInstance(context,this);

this.defaultDrawable = context.getResources().getDrawable(

com.littlerain.ui.R.drawable.skinclassic_default_thumbnai);

this.ctx = context;

}

@Override

protected void bindChildView(View view, Context context, Cursor cursor,

boolean isLastChild) {

// TODO Auto-generatedmethod stub

childCache = (ChildViewCache) view.getTag();

// 显示名字

cursor.copyStringToBuffer(cursor.getColumnIndex(Contacts.DISPLAY_NAME),

childCache.nameBuffer);

int size =childCache.nameBuffer.sizeCopied;

childCache.nameView.setText(childCache.nameBuffer.data, 0, size);

/* 显示头像 */

long photoId = cursor.getLong(cursor.getColumnIndex(Contacts.PHOTO_ID));

childCache.photoView.setImageDrawable(photoCache.getHeadImg(photoId)

.getHead());

final String lookupKey = cursor.getString(cursor

.getColumnIndex(Contacts.LOOKUP_KEY));

childCache.photoView.assignContactUri(Contacts.getLookupUri(

cursor.getLong(cursor.getColumnIndex(Data.CONTACT_ID)),

lookupKey));

/* 显示自定义信息 */

String ringstoneUri = null;

ringstoneUri = cursor.getString(cursor

.getColumnIndex(Contacts.CUSTOM_RINGTONE));

if (ringstoneUri ==null) {

childCache.info.setText("铃声:默认");

} else {

Cursor c = ctx.getContentResolver().query(Uri.parse(ringstoneUri),

new String[] { MediaColumns.TITLE },null,null,

null);

if (c.moveToNext()) {

childCache.info.setText("铃声:"

+ c.getString(c

.getColumnIndex(MediaColumns.TITLE)));

}

view.setId((int) cursor.getLong(cursor.getColumnIndex(Data.CONTACT_ID)));

}

@Override

protected void bindGroupView(View view, Context context, Cursor cursor,

boolean isExpanded) {

cache = (GroupViewCache) view.getTag();

cache.groupName.setText(cursor.getString(cursor

.getColumnIndex(Groups.TITLE)));

cache.groupCount.setText("["

+ ContactsManager.getInstance().getMemberCountByGroupId(

cursor.getString(cursor.getColumnIndex(BaseColumns._ID)))

+ "]");

view.setId((int) cursor.getLong(cursor.getColumnIndex(BaseColumns._ID)));

}

@Override

protected Cursor getChildrenCursor(Cursor groupCursor) {

// TODO Auto-generatedmethod stub

Cursor c = ContactsManager.getInstance().getGroupMember(

groupCursor.getString(groupCursor.getColumnIndex(BaseColumns._ID)));

return c;

}

@Override

protected View newChildView(Context context, Cursor cursor,

boolean isLastChild, ViewGroup parent) {

// TODO Auto-generatedmethod stub

LayoutInflater inflater = LayoutInflater.from(context);

View view = inflater.inflate(R.layout.contact_layout,null);

ChildViewCache cache = new ChildViewCache();

cache.nameView = (TextView) view

.findViewById(com.littlerain.ui.R.id.contact_name);

cache.photoView = (QuickContactBadge) view

.findViewById(com.littlerain.ui.R.id.contact_head);

cache.info = (TextView) view

.findViewById(com.littlerain.ui.R.id.contact_info);

view.setTag(cache);

return view;

}

@Override

protected ViewnewGroupView(Contextcontext, Cursor cursor,

boolean isExpanded, ViewGroup parent) {

// TODO Auto-generatedmethod stub

LayoutInflater inflater = LayoutInflater.from(context);

View view = inflater.inflate(R.layout.group_list_view,null);

GroupViewCache cache = new GroupViewCache();

cache.groupName = (TextView) view.findViewById(R.id.group_name);

cache.groupCount = (TextView) view

.findViewById(R.id.group_member_count);

view.setTag(cache);

return view;

}

final class GroupViewCache {

public TextViewgroupName;

public TextViewgroupCount;

}

final class ChildViewCache {

public TextViewnameView;

public QuickContactBadgephotoView;

public TextViewinfo;

public CharArrayBuffernameBuffer =new CharArrayBuffer(128);

}

@Override

public boolean isChildSelectable(int groupPosition,int childPosition) {

// TODO Auto-generatedmethod stub

return true;

}

需要实现的方法有bindChildView，bindGroupView，getChildrenCursor，newChildView，newGroupView。其中newChildView是每个分组里的子列表每个列表的view，newGroupView是每个分组的标题列表的view。BindChildView及bindGroupView是分别将数据render到相应的view上。getChildrenCursor是为子列表获取Cursor。之后在需要的Activity中使用以下代码即可：

GroupListAdapter adapter = newGroupListAdapter(groupCursor, this, true);

setListAdapter(adapter);

getExpandableListView().setCacheColorHint(0);//拖动时避免出现黑色

getExpandableListView().setDivider(null);//去掉每项下面的黑线(分割线)

getExpandableListView().setGroupIndicator(

getResources().getDrawable(R.drawable.expander_ic_folder));//自定义下拉图标

以上只是对ExpandableListActivity作了一个入门的介绍，帮助大家快速上手。若要详细了解具体的每个方法，请自行查阅Android SDK。

from:http://blog.csdn.net/pku_android/article/details/7597282

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