Android版手风琴(ExpandableListView)

先看效果，过瘾一番。

ExpandableListView是Android中的手风琴，本人感觉效果相当棒。

一、ExpandableListView介绍

一个垂直滚动的显示两个级别（Child,Group）列表项的视图，列表项来自ExpandableListAdapter 。组可以单独展开。

1.重要方法

expandGroup(int groupPos) :在分组列表视图中展开一组，
setSelectedGroup(int groupPosition) ：设置选择指定的组。
setSelectedChild(int groupPosition, int childPosition, boolean shouldExpandGroup) ：设置选择指定的子项。
getPackedPositionGroup(long packedPosition) ：返回所选择的组
getPackedPositionForChild(int groupPosition, int childPosition) ：返回所选择的子项
getPackedPositionType(long packedPosition) ：返回所选择项的类型（Child,Group）
isGroupExpanded(int groupPosition) :判断此组是否展开

2.代码：

ExpandableListContextMenuInfo menuInfo=(ExpandableListContextMenuInfo)item.getMenuInfo();
String title=((TextView)menuInfo.targetView).getText().toString();
int type=ExpandableListView.getPackedPositionType(menuInfo.packedPosition);
  
if (type==ExpandableListView.PACKED_POSITION_TYPE_CHILD) {
    int groupPos =ExpandableListView.getPackedPositionGroup(menuInfo.packedPosition);
    int childPos =ExpandableListView.getPackedPositionChild(menuInfo.packedPosition);
}

二、ExpandableListAdapter

一个接口，将基础数据链接到一个ExpandableListView。此接口的实施将提供访问Child的数据（由组分类），并实例化的Child和Group。

1.重要方法

getChildId(int groupPosition, int childPosition) //获取与在给定组给予孩子相关的数据。
getChildrenCount(int groupPosition) //返回在指定Group的Child数目。

2.代码

public class MyExpandableListAdapter extends BaseExpandableListAdapter {
    // Sample data set.  children[i] contains the children (String[]) for groups[i].
    public String[] groups = { "我的好友", "新疆同学", "亲戚", "同事" };
    public String[][] children = {
        { "胡算林", "张俊峰", "王志军", "二人" },
        { "李秀婷", "蔡乔", "别高", "余音" },
        { "摊派新", "张爱明" },
        { "马超", "司道光" }
    };

    public Object getChild(int groupPosition, int childPosition) {
        return children[groupPosition][childPosition];
    }

    public long getChildId(int groupPosition, int childPosition) {
        return childPosition;
    }

    public int getChildrenCount(int groupPosition) {
        return children[groupPosition].length;
    }

    public TextView getGenericView() {
        // Layout parameters for the ExpandableListView
        AbsListView.LayoutParams lp = new AbsListView.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, 64);

        TextView textView = new TextView(ExpandableListDemo.this);
        textView.setLayoutParams(lp);
        // Center the text vertically
        textView.setGravity(Gravity.CENTER_VERTICAL | Gravity.LEFT);
        // Set the text starting position
        textView.setPadding(36, 0, 0, 0);
        return textView;
    }
 
    public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
        TextView textView = getGenericView();
        textView.setText(getChild(groupPosition, childPosition).toString());
        return textView;
    }

    public Object getGroup(int groupPosition) {
        return groups[groupPosition];
    }

    public int getGroupCount() {
        return groups.length;
    }

    public long getGroupId(int groupPosition) {
        return groupPosition;
    }

    public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {
        TextView textView = getGenericView();
        textView.setText(getGroup(groupPosition).toString());
        return textView;
    }

    public boolean isChildSelectable(int groupPosition, int childPosition) {
        return true;
    }

    public boolean hasStableIds() {
        return true;
    }

}