ExpandableList的用法

package com.android.osb;

import android.app.ExpandableListActivity;
import android.os.Bundle;
import android.view.ContextMenu;
import android.view.ContextMenu.ContextMenuInfo;
import android.view.Gravity;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewGroup.LayoutParams;
import android.widget.AbsListView;
import android.widget.BaseExpandableListAdapter;
import android.widget.ExpandableListAdapter;
import android.widget.ExpandableListView;
import android.widget.Toast;
import android.widget.ExpandableListView.ExpandableListContextMenuInfo;
import android.widget.TextView;

public class ExpandableList extends ExpandableListActivity {

    private ExpandableListAdapter expandableListAdapter;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        expandableListAdapter = new MyExpandable();
        
        //设置ListAdapter的Adapter为继承自BaseExpandableListAdapter的一个Adapter
        setListAdapter(expandableListAdapter);
        
        //注册长按菜单
        registerForContextMenu(this.getExpandableListView());
    }
    
    @Override
    public void onCreateContextMenu(ContextMenu menu, View v,
            ContextMenuInfo menuInfo) {
        // TODO Auto-generated method stub
        
        //弹出的长按菜单的标题
        menu.setHeaderTitle("ContextMenu");
        
        //弹出的长按菜单的选项
        menu.add(0, 0, 0, "ContextMenu");
    }
    
    
    //点击长按菜单选项的处理事件
    @Override
    public boolean onContextItemSelected(MenuItem item) {
        // TODO Auto-generated method stub
        
        //从MenuItem中拿到ContextMenuInfo，并强制转换成ExpandableListContextMenuInfo.
        ExpandableListContextMenuInfo info = (ExpandableListContextMenuInfo) item.getMenuInfo();
        //将info中的contextMenu正在显示的View的标题拿到，并强制转换成TextView.
        String title = ((TextView)info.targetView).getText().toString();
        
        //从info中拿到packedPosition，并根据packedPosition判断ExpandableListView的类型，是child还是group。
        int type = ExpandableListView.getPackedPositionType(info.packedPosition);
        if(type == ExpandableListView.PACKED_POSITION_TYPE_CHILD) {
            int groupPos = ExpandableListView.getPackedPositionGroup(info.packedPosition);
            int childPos = ExpandableListView.getPackedPositionChild(info.packedPosition);
            //如果是child，从ExpandableListView中拿到groupPos和childPos.并显示出来。
            Toast.makeText(this, "title : " + title + ", groupPos : " + groupPos + ", childPos : " + childPos, Toast.LENGTH_LONG).show();
            return true;
        } else if(type == ExpandableListView.PACKED_POSITION_TYPE_GROUP) {
            int groupPos = ExpandableListView.getPackedPositionGroup(info.packedPosition);
            //如果是group，从ExpandableListView中拿到groupPos并显示出来。
            Toast.makeText(this, "title : " + title + ", groupPos : " + groupPos, Toast.LENGTH_LONG).show();
            return true;
        }
        return false;
    }
    
    //这个Adapter是继承BaseExpandableListAdapter的。
    private class MyExpandable extends BaseExpandableListAdapter {

        //父列表数据
        private String[] groups = {
                "group1",
                "group2",
                "group3",
                "group4"
        };
        
        //子列表数据
        private String[][] children = {
                {"child1"},
                {"child1","child2"},
                {"child1", "child2", "child3"},
                {"child1", "child2", "child3", "child4"}
        };
        
        //根据groupPosition和childPosition拿到child的对象
        @Override
        public Object getChild(int groupPosition, int childPosition) {
            // TODO Auto-generated method stub
            return children[groupPosition][childPosition];
        }

        
        //根据childPosition拿到child的ID
        @Override
        public long getChildId(int groupPosition, int childPosition) {
            // TODO Auto-generated method stub
            return childPosition;
        }

        @Override
        public View getChildView(int groupPosition, int childPosition, boolean isLastchild, View convertView,
                ViewGroup parent) {
            // TODO Auto-generated method stub
            //创建一个TextView，并将child对象转换成字符串显示在TextView上面。
            TextView tv = getGenericView();
            tv.setText(getChild(groupPosition, childPosition).toString());
            return tv;
        }

        //根据groupPosition拿到children的长度。
        @Override
        public int getChildrenCount(int groupPosition) {
            // TODO Auto-generated method stub
            return children[groupPosition].length;
        }

        //根据groupPosition拿到group的对象
        @Override
        public Object getGroup(int groupPosition) {
            // TODO Auto-generated method stub
            return groups[groupPosition];
        }

        @Override
        public int getGroupCount() {
            // TODO Auto-generated method stub
            return groups.length;
        }

        @Override
        public long getGroupId(int groupPosition) {
            // TODO Auto-generated method stub
            return groupPosition;
        }

        @Override
        public View getGroupView(int groupPosition, boolean isExpanded, View convertView,
                ViewGroup parent) {
            // TODO Auto-generated method stub
            //创建一个TextView，并将group对象转换成字符串显示在TextView上面。
            TextView tv = getGenericView();
            tv.setText(getGroup(groupPosition).toString());
            return tv;
        }

        @Override
        public boolean hasStableIds() {
            // TODO Auto-generated method stub
            return true;
        }

        @Override
        public boolean isChildSelectable(int groupPosition, int childPosition) {
            // TODO Auto-generated method stub
            return true;
        }
        
        //创建一个新的TextView对象。
        private TextView getGenericView () {
            TextView tv = new TextView(ExpandableList.this);
            tv.setLayoutParams(new AbsListView.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
            tv.setGravity(Gravity.CENTER_VERTICAL|Gravity.LEFT);
            tv.setPadding(32, 0, 0, 0);
            return tv;
        }
    }
}