06.实例篇：仿QQ好友列表——ExpandableListView和ListView（下篇）

1.前言

本篇主要ExpandableListView和ListView一些基础知识点介绍，主要包括一些类和接口的使用介绍，主要是参照google 最新的API文档摘要总结的；

2.什么是ListView

是一种ViewGroup，用于滚动展示一组列表，这些列表项自动由Adapter从数据源读取数据产生特定的View填充到ListView；
当布局中的内容是动态的或者预先不可知的，可以使用AdapterView（ListView,GridView是其子类）运行时填充；
AdapterView（包括子类）使用Adapter绑定数据到自己，Adapter是数据源和AdapterView布局的中介；

3.ListView重要方法和属性：

  用于垂直滚动列表视图，列表项来自ListAdapter；
  类继承结构：具体的类
  public class  ListView  extends AbsListView 
    java.lang.Object
       ↳ android.view.View
         ↳ android.view.ViewGroup
           ↳ android.widget.AdapterView<T extends android.widget.Adapter>
                ↳ android.widget.AbsListView
                   ↳ android.widget.ListView
  直接子类：
        ExpandableListView ：用于展示两级列表；
 
  重要的XML属性：
    android:divider：两个列表项之间的分割线（可以使color或者Drawable）
    android:dividerHeight：分割线的高度（厚度）
    android:entries：静态引用一个数组资源，用来填充ListView的
    android:footerDividersEnabled：对于footer view是否有divider
    android:headerDividersEnabled:
  从AbsListView继承的重要属性：
    android:choiceMode:设置列表项的选择行为，是否可以选择，是否支持多选
    android:listSelector ：设置列表中被选中的项的Drawable
    android:textFilterEnabled：是否支持过滤

  重要方法：
      void  addFooterView(View v)：添加固定的View到列表的底部，在setAdapter之前调用，可以添加多次，显示多个
      void addFooterView(View v, Object data, boolean isSelectable)      
      void addHeaderView(View v)
    
      ListAdapter getAdapter()：返回与之绑定的Adapter
      void setAdapter (ListAdapter adapter) ：设置ListView的数据

      long[] getCheckItemIds ()：api8过期，获取选择的多个Items的id，仅当模式不是CHOICE_MODE_NONE.有效
      void setSelection (int position)：设置选定的列表项，从0开始

4.ListView相关的类：ListAdapter（也是接口）

   public interface Adapter  android.widget.Adapter    
   间接子类：
   ArrayAdapter<T>, BaseAdapter, CursorAdapter, HeaderViewListAdapter, ListAdapter,    
   ResourceCursorAdapter, SimpleAdapter, SimpleCursorAdapter,SpinnerAdapter, WrapperListAdapter 
   方法：
   abstract int getCount()：有多少数据
   abstract Object getItem(int position):获取特定位置的数据
   abstract long    getItemId(int position):获取特定位置的行id
   abstract View getView(int position, View convertView, ViewGroup parent)：获取特定位置展示的View
   abstract boolean isEmpty()：
  
   public interface ListAdapter implements Adapter （添加了两个抽象方法） android.widget.ListAdapter
   间接子类：
   ArrayAdapter<T>, BaseAdapter（抽象类）, CursorAdapter（抽象类）, HeaderViewListAdapter, 
   ResourceCursorAdapter, SimpleAdapter, SimpleCursorAdapter, WrapperListAdapter
     
   常用的Adapter：
   public class ArrayAdapter extends BaseAdapter implements Filterable：android.widget.ArrayAdapter<T>
   具体简单的Adapter类，数据源是数组，布局中有一个简单的TextView，如果想要其它View，可以重写getView方法
   使用一般重写，或者使用：
   public ArrayAdapter (Context context, int resource, T[] objects)：Resource布局文件必须有特定名称的textview
   public ArrayAdapter (Context context, int resource, int textViewResourceId, T[] objects)
   public ArrayAdapter (Context context, int resource, List<T> objects)
   public ArrayAdapter (Context context, int resource, int textViewResourceId, List<T> objects)
    
   public class  SimpleCursorAdapter extends ResourceCursorAdapter：

   android.support.v4.widget.SimpleCursorAdapter

   构造器：
   SimpleCursorAdapter(Context context, int layout, Cursor c, String[] from, int[] to, int flags)
   参数：layout-定义列表项的布局文件，c-数据源cursor，可以为null（如果不可用），
             from-数组定义了需要绑定的cursor数据列名，to-表明view的id，用来展示数据
             flags-决定adapter的行为，FLAG_AUTO_REQUERY（过期，不建议使用，会在主线程中获取数据，阻塞）                 FLAG_REGISTER_CONTENT_OBSERVER（添加内容监听器，当通知到来，

调用onContentChanged方法，小心内存泄露，当使用CursorAdapter[CursorLoader]时，不需要该标志；

   方法：
   Cursor swapCursor(Cursor c)：换入一个新的Cursor，返回旧的cursor【未关闭】，如果cursor为null或者新的和旧的一样返回null
   public abstract class  CursorAdapter  extends BaseAdapter implements Filterable

5.ListView使用方式：【读取本地数据】

•     需要ListView；
•    需要ListAdapter及其子类；
•    如果Adpater数据发生变化，应该调用notifyDataSetChanged()方法；

   ListView+ArrayAdapter方法：
   定制每一项文本内容，可以重写数组中每个对象的toString方法；
   定制ListView每一项的视图，可以重写getView方法；

   ArrayAdapter adapter = new ArrayAdapter<String>(this,        android.R.layout.simple_list_item_1, myStringArray);   ListView listView = (ListView) findViewById(R.id.listview);   listView.setAdapter(adapter);

   ListView+SimpleCursorAdapter方法：

   String[] fromColumns = {ContactsContract.Data.DISPLAY_NAME,                        ContactsContract.CommonDataKinds.Phone.NUMBER};   int[] toViews = {R.id.display_name, R.id.phone_number};   SimpleCursorAdapter adapter = new SimpleCursorAdapter(this,         R.layout.person_name_and_number, cursor, fromColumns, toViews, 0);   ListView listView = getListView();   listView.setAdapter(adapter);

   处理点击事件：实现AdapterView.onItemClickListener接口

<pre name="code" class="java">    // Create a message handling object as an anonymous class.    private OnItemClickListener mMessageClickedHandler = new OnItemClickListener() {        public void onItemClick(AdapterView parent, View v, int position, long id) {        // Do something in response to the click        }    };    listView.setOnItemClickListener(mMessageClickedHandler); 

   使用CursorLoader+ListView方法：   

  public class ListViewLoader extends ListActivity        implements LoaderManager.LoaderCallbacks<Cursor> {    // This is the Adapter being used to display the list's data    SimpleCursorAdapter mAdapter;    // These are the Contacts rows that we will retrieve    static final String[] PROJECTION = new String[] {ContactsContract.Data._ID,            ContactsContract.Data.DISPLAY_NAME};    // This is the select criteria    static final String SELECTION = "((" +             ContactsContract.Data.DISPLAY_NAME + " NOTNULL) AND (" +            ContactsContract.Data.DISPLAY_NAME + " != '' ))";    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        // Create a progress bar to display while the list loads        ProgressBar progressBar = new ProgressBar(this);        progressBar.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT,                LayoutParams.WRAP_CONTENT, Gravity.CENTER));        progressBar.setIndeterminate(true);        getListView().setEmptyView(progressBar);        // Must add the progress bar to the root of the layout        ViewGroup root = (ViewGroup) findViewById(android.R.id.content);        root.addView(progressBar);        // For the cursor adapter, specify which columns go into which views        String[] fromColumns = {ContactsContract.Data.DISPLAY_NAME};        int[] toViews = {android.R.id.text1}; // The TextView in simple_list_item_1        // Create an empty adapter we will use to display the loaded data.        // We pass null for the cursor, then update it in onLoadFinished()        mAdapter = new SimpleCursorAdapter(this,                 android.R.layout.simple_list_item_1, null,                fromColumns, toViews, 0);        setListAdapter(mAdapter);        // Prepare the loader.  Either re-connect with an existing one,        // or start a new one.        getLoaderManager().initLoader(0, null, this);    }    // Called when a new Loader needs to be created    public Loader<Cursor> onCreateLoader(int id, Bundle args) {        // Now create and return a CursorLoader that will take care of        // creating a Cursor for the data being displayed.        return new CursorLoader(this, ContactsContract.Data.CONTENT_URI,                PROJECTION, SELECTION, null, null);    }    // Called when a previously created loader has finished loading    public void onLoadFinished(Loader<Cursor> loader, Cursor data) {        // Swap the new cursor in.  (The framework will take care of closing the        // old cursor once we return.)        mAdapter.swapCursor(data);    }    // Called when a previously created loader is reset, making the data unavailable    public void onLoaderReset(Loader<Cursor> loader) {        // This is called when the last Cursor provided to onLoadFinished()        // above is about to be closed.  We need to make sure we are no        // longer using it.        mAdapter.swapCursor(null);    }    @Override     public void onListItemClick(ListView l, View v, int position, long id) {        // Do something when a list item is clicked    }}  

5.ListView动态获取网络数据方式【见下一节文章】

6.ExpandableListView相关类和知识点

   public class  ExpandableListView extends ListView：ListView的子类，android.widget.ExpandableListView
   两级列表，分为组和组中Items，使用ExpandableListAdapter接口提供数据；

   重要的接口：
   ExpandableListView.OnChildClickListener 、ExpandableListView.OnGroupClickListener
   ExpandableListView.OnGroupCollapseListener 、ExpandableListView.OnGroupExpandListener

   重要的XML属性：
   android:childDivider：color或者Drawable资源文件，子项目的分隔符
   android:childIndicator ：状态列表的Drawable资源文件，用于定义子项目各种状态对应的效果
   android:groupIndicator 

   重要方法：
   ExpandableListAdapter getExpandableListAdapter()：
   boolean collapseGroup(int groupPos)
   boolean expandGroup(int groupPos)
   boolean expandGroup(int groupPos, boolean animate)
   long getSelectedPosition()：获取选择Group或者child的位置，该位置是打包以后的；综合的
   long getSelectedId ()：获取已经选择的Group或者child的id，如果没选择，则返回-1；
   static int getPackedPositionChild(long packedPosition)  
   public boolean setSelectedChild (int groupPosition, int childPosition, boolean shouldExpandGroup)
   public void setSelectedGroup (int groupPosition)

   相关的类：public interface ExpandableListAdapter：按Group组织数据，为可展开类别提供数据；
   间接子类：
   BaseExpandableListAdapter, CursorTreeAdapter, ResourceCursorTreeAdapter, 
   SimpleCursorTreeAdapter, SimpleExpandableListAdapter
   
   SimpleExpandableListAdapter：

   注意groupTo和ChildTo所对应的视图都是TextView才行（ImageView不行，其它类型的视图，需要重写getGroupView和getChildView方法；）；
       简单的Adapter映射静态数据到group和child view。
       构造器：9个参数

       SimpleExpandableListAdapter(Context context, List<? extends Map<String, ?>> groupData, int groupLayout,                 String[] groupFrom, int[] groupTo, List<? extends List<? extends Map<String, ?>>> childData,                 int childLayout, String[] childFrom, int[] childTo)

                 context：AdapterView运行环境上下文
                 groupData:Map的列表，列表中的每一项代表一组所有属性数据，Map包含组的数据，至少包含groupFrom所有的条目，例如每个Group需要一个textView和ImageView，那么可以map1.put("text","xxxx"); map1.put("image", "ddd")作为第一组的group Item；
                 groupLayout:Group视图的布局文件id，至少包含groupTo中的所有组件id
                 groupFrom：一组keys（用于获取每个组的数据，因为一个组项view可能需要多个数据），用于从Maps获取关联的该组view的数据
                 groupTo：一组view id，用于对应展示groupFrom中列数据
                 childData：Map对象列表的列表，外围的列表代表每个组，里面的列表代表每一组里面的项所有属性数据；

 其它参数类似；   

       SimpleExpandableListAdapter(Context context, List<? extends Map<String, ?>> groupData,                 int expandedGroupLayout, int collapsedGroupLayout, String[] groupFrom,                int[] groupTo, List<? extends List<? extends Map<String, ?>>> childData,                 int childLayout, String[] childFrom, int[] childTo)       SimpleExpandableListAdapter(Context context, List<? extends Map<String, ?>> groupData,                int expandedGroupLayout, int collapsedGroupLayout, String[] groupFrom, int[] groupTo,                 List<? extends List<? extends Map<String, ?>>> childData, int childLayout,                 int lastChildLayout, String[] childFrom, int[] childTo)

        SimpleCursorTreeAdapter：
        

SimpleCursorTreeAdapter(Context context, Cursor cursor, int collapsedGroupLayout,                 int expandedGroupLayout, String[] groupFrom, int[] groupTo, int childLayout,                  int lastChildLayout, String[] childFrom, int[] childTo)        SimpleCursorTreeAdapter(Context context, Cursor cursor, int collapsedGroupLayout,                 int expandedGroupLayout, String[] groupFrom, int[] groupTo, int childLayout,                 String[] childFrom, int[] childTo)        SimpleCursorTreeAdapter(Context context, Cursor cursor, int groupLayout, String[] groupFrom,                 int[] groupTo, int childLayout, String[] childFrom, int[] childTo)

7.ExpandableListView的使用实例

    参见上篇文章：http://blog.csdn.net/meplusplus/article/details/26622261

8.如何定制自己的ExpandableListAdapter

     主要是学习系统的源码实现，继承已有的ListAdapter，以下是系统SimpleExpandableListAdapter的源码实现，我们可以继承然后重写getChildView和getGroupView方法；

package android.widget;import android.content.Context;import android.view.View;import android.view.ViewGroup;import android.view.LayoutInflater;import java.util.List;import java.util.Map;/** * An easy adapter to map static data to group and child views defined in an XML * file. You can separately specify the data backing the group as a List of * Maps. Each entry in the ArrayList corresponds to one group in the expandable * list. The Maps contain the data for each row. You also specify an XML file * that defines the views used to display a group, and a mapping from keys in * the Map to specific views. This process is similar for a child, except it is * one-level deeper so the data backing is specified as a List<List<Map>>, * where the first List corresponds to the group of the child, the second List * corresponds to the position of the child within the group, and finally the * Map holds the data for that particular child. */public class SimpleExpandableListAdapter extends BaseExpandableListAdapter {    private List<? extends Map<String, ?>> mGroupData;    private int mExpandedGroupLayout;    private int mCollapsedGroupLayout;    private String[] mGroupFrom;    private int[] mGroupTo;        private List<? extends List<? extends Map<String, ?>>> mChildData;    private int mChildLayout;    private int mLastChildLayout;    private String[] mChildFrom;    private int[] mChildTo;        private LayoutInflater mInflater;        /**     * Constructor     *      * @param context The context where the {@link ExpandableListView}     *            associated with this {@link SimpleExpandableListAdapter} is     *            running     * @param groupData A List of Maps. Each entry in the List corresponds to     *            one group in the list. The Maps contain the data for each     *            group, and should include all the entries specified in     *            "groupFrom"     * @param groupFrom A list of keys that will be fetched from the Map     *            associated with each group.     * @param groupTo The group views that should display column in the     *            "groupFrom" parameter. These should all be TextViews. The     *            first N views in this list are given the values of the first N     *            columns in the groupFrom parameter.     * @param groupLayout resource identifier of a view layout that defines the     *            views for a group. The layout file should include at least     *            those named views defined in "groupTo"     * @param childData A List of List of Maps. Each entry in the outer List     *            corresponds to a group (index by group position), each entry     *            in the inner List corresponds to a child within the group     *            (index by child position), and the Map corresponds to the data     *            for a child (index by values in the childFrom array). The Map     *            contains the data for each child, and should include all the     *            entries specified in "childFrom"     * @param childFrom A list of keys that will be fetched from the Map     *            associated with each child.     * @param childTo The child views that should display column in the     *            "childFrom" parameter. These should all be TextViews. The     *            first N views in this list are given the values of the first N     *            columns in the childFrom parameter.     * @param childLayout resource identifier of a view layout that defines the     *            views for a child. The layout file should include at least     *            those named views defined in "childTo"     */    public SimpleExpandableListAdapter(Context context,            List<? extends Map<String, ?>> groupData, int groupLayout,            String[] groupFrom, int[] groupTo,            List<? extends List<? extends Map<String, ?>>> childData,            int childLayout, String[] childFrom, int[] childTo) {        this(context, groupData, groupLayout, groupLayout, groupFrom, groupTo, childData,                childLayout, childLayout, childFrom, childTo);    }    /**     * Constructor     *      * @param context The context where the {@link ExpandableListView}     *            associated with this {@link SimpleExpandableListAdapter} is     *            running     * @param groupData A List of Maps. Each entry in the List corresponds to     *            one group in the list. The Maps contain the data for each     *            group, and should include all the entries specified in     *            "groupFrom"     * @param groupFrom A list of keys that will be fetched from the Map     *            associated with each group.     * @param groupTo The group views that should display column in the     *            "groupFrom" parameter. These should all be TextViews. The     *            first N views in this list are given the values of the first N     *            columns in the groupFrom parameter.     * @param expandedGroupLayout resource identifier of a view layout that     *            defines the views for an expanded group. The layout file     *            should include at least those named views defined in "groupTo"     * @param collapsedGroupLayout resource identifier of a view layout that     *            defines the views for a collapsed group. The layout file     *            should include at least those named views defined in "groupTo"     * @param childData A List of List of Maps. Each entry in the outer List     *            corresponds to a group (index by group position), each entry     *            in the inner List corresponds to a child within the group     *            (index by child position), and the Map corresponds to the data     *            for a child (index by values in the childFrom array). The Map     *            contains the data for each child, and should include all the     *            entries specified in "childFrom"     * @param childFrom A list of keys that will be fetched from the Map     *            associated with each child.     * @param childTo The child views that should display column in the     *            "childFrom" parameter. These should all be TextViews. The     *            first N views in this list are given the values of the first N     *            columns in the childFrom parameter.     * @param childLayout resource identifier of a view layout that defines the     *            views for a child. The layout file should include at least     *            those named views defined in "childTo"     */    public SimpleExpandableListAdapter(Context context,            List<? extends Map<String, ?>> groupData, int expandedGroupLayout,            int collapsedGroupLayout, String[] groupFrom, int[] groupTo,            List<? extends List<? extends Map<String, ?>>> childData,            int childLayout, String[] childFrom, int[] childTo) {        this(context, groupData, expandedGroupLayout, collapsedGroupLayout,                groupFrom, groupTo, childData, childLayout, childLayout,                childFrom, childTo);    }    /**     * Constructor     *      * @param context The context where the {@link ExpandableListView}     *            associated with this {@link SimpleExpandableListAdapter} is     *            running     * @param groupData A List of Maps. Each entry in the List corresponds to     *            one group in the list. The Maps contain the data for each     *            group, and should include all the entries specified in     *            "groupFrom"     * @param groupFrom A list of keys that will be fetched from the Map     *            associated with each group.     * @param groupTo The group views that should display column in the     *            "groupFrom" parameter. These should all be TextViews. The     *            first N views in this list are given the values of the first N     *            columns in the groupFrom parameter.     * @param expandedGroupLayout resource identifier of a view layout that     *            defines the views for an expanded group. The layout file     *            should include at least those named views defined in "groupTo"     * @param collapsedGroupLayout resource identifier of a view layout that     *            defines the views for a collapsed group. The layout file     *            should include at least those named views defined in "groupTo"     * @param childData A List of List of Maps. Each entry in the outer List     *            corresponds to a group (index by group position), each entry     *            in the inner List corresponds to a child within the group     *            (index by child position), and the Map corresponds to the data     *            for a child (index by values in the childFrom array). The Map     *            contains the data for each child, and should include all the     *            entries specified in "childFrom"     * @param childFrom A list of keys that will be fetched from the Map     *            associated with each child.     * @param childTo The child views that should display column in the     *            "childFrom" parameter. These should all be TextViews. The     *            first N views in this list are given the values of the first N     *            columns in the childFrom parameter.     * @param childLayout resource identifier of a view layout that defines the     *            views for a child (unless it is the last child within a group,     *            in which case the lastChildLayout is used). The layout file     *            should include at least those named views defined in "childTo"     * @param lastChildLayout resource identifier of a view layout that defines     *            the views for the last child within each group. The layout     *            file should include at least those named views defined in     *            "childTo"     */    public SimpleExpandableListAdapter(Context context,            List<? extends Map<String, ?>> groupData, int expandedGroupLayout,            int collapsedGroupLayout, String[] groupFrom, int[] groupTo,            List<? extends List<? extends Map<String, ?>>> childData,            int childLayout, int lastChildLayout, String[] childFrom,            int[] childTo) {        mGroupData = groupData;        mExpandedGroupLayout = expandedGroupLayout;        mCollapsedGroupLayout = collapsedGroupLayout;        mGroupFrom = groupFrom;        mGroupTo = groupTo;                mChildData = childData;        mChildLayout = childLayout;        mLastChildLayout = lastChildLayout;        mChildFrom = childFrom;        mChildTo = childTo;                mInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);    }        public Object getChild(int groupPosition, int childPosition) {        return mChildData.get(groupPosition).get(childPosition);    }    public long getChildId(int groupPosition, int childPosition) {        return childPosition;    }    public View getChildView(int groupPosition, int childPosition, boolean isLastChild,            View convertView, ViewGroup parent) {        View v;        if (convertView == null) {            v = newChildView(isLastChild, parent);        } else {            v = convertView;        }        bindView(v, mChildData.get(groupPosition).get(childPosition), mChildFrom, mChildTo);        return v;    }    /**     * Instantiates a new View for a child.     * @param isLastChild Whether the child is the last child within its group.     * @param parent The eventual parent of this new View.     * @return A new child View     */    public View newChildView(boolean isLastChild, ViewGroup parent) {        return mInflater.inflate((isLastChild) ? mLastChildLayout : mChildLayout, parent, false);    }        private void bindView(View view, Map<String, ?> data, String[] from, int[] to) {        int len = to.length;        for (int i = 0; i < len; i++) {            TextView v = (TextView)view.findViewById(to[i]);            if (v != null) {                v.setText((String)data.get(from[i]));            }        }    }    public int getChildrenCount(int groupPosition) {        return mChildData.get(groupPosition).size();    }    public Object getGroup(int groupPosition) {        return mGroupData.get(groupPosition);    }    public int getGroupCount() {        return mGroupData.size();    }    public long getGroupId(int groupPosition) {        return groupPosition;    }    public View getGroupView(int groupPosition, boolean isExpanded, View convertView,            ViewGroup parent) {        View v;        if (convertView == null) {            v = newGroupView(isExpanded, parent);        } else {            v = convertView;        }        bindView(v, mGroupData.get(groupPosition), mGroupFrom, mGroupTo);        return v;    }    /**     * Instantiates a new View for a group.     * @param isExpanded Whether the group is currently expanded.     * @param parent The eventual parent of this new View.     * @return A new group View     */    public View newGroupView(boolean isExpanded, ViewGroup parent) {        return mInflater.inflate((isExpanded) ? mExpandedGroupLayout : mCollapsedGroupLayout,                parent, false);    }    public boolean isChildSelectable(int groupPosition, int childPosition) {        return true;    }    public boolean hasStableIds() {        return true;    }}

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