Using Android API Level : 7 
This article will try to cover aspects of creating Expandable List at runtime.
By "runtime", I mean to say not by using Android XML file for layout and Views 
but with the help of coding using Android API such as 
"android.app.ExpandableListActivity" 
"android.widget.BaseExpandableListAdapter"

After preparing/setting-up Software Environment for developing Mobile Application on 
Android Platform, for me initial task is to formulate idea as to how this application
is going to behave at run-time. For example I choose to use Expandable List View
for showing various categories/varieties of items within each group in form of List.

I choose to show "cup-boards" and "Cameras" as shopping items on display within this
ListView.On click of each item there will be sub/child elements/items getting 
displayed below the main selectable section/header.

Following images are going to show the actual screen that is expected at the time of
execution of this example source code:

Initial screen on invocation of this application:


On click/touch of the first category following image shows the sub-elements:


On click/touch of the second/subsequent category following image shows 
the sub-elements:


On click/touch of the both categories following image shows the sub-elements:


Let us go through the files used as far as this example is concerned:

Example Project on Android Platform main.xml file:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">
    <ExpandableListView android:id="@android:id/list" 
              android:layout_width="fill_parent" 
              android:layout_height="fill_parent"
              android:background="#ffffff"/>
</LinearLayout>



ExpandableListViewExample.java

package com.techienjoy.example.expandablelistview;

import android.app.ExpandableListActivity;
import android.content.Context;
import android.graphics.Color;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseExpandableListAdapter;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.TextView;

public class ExpandableListViewExample extends ExpandableListActivity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        setListAdapter(new ExampleAdapter(this));        
    }
    
    private class ExampleAdapter extends BaseExpandableListAdapter {
        private Context context;
    	public ExampleAdapter(Context context) {
    		this.context = context;
    	}
		@Override
		public Object getChild(int groupPosition, int childPosition) {
			return null;
		}
		@Override
		public long getChildId(int groupPosition, int childPosition) {
			return 0;
		}
		
		/**
		 *  getChildView overridden method will have responsibility of
		 *  constructing View for the child element when corresponding
		 *  group element is activated by click / touch action.
		 */
		 
		@Override
		public View getChildView(int groupPosition, int childPosition,
				boolean isLastChild, View convertView, ViewGroup parent) {
			LinearLayout linear = new LinearLayout(this.context);
			ImageView imView1 = null;
			ImageView imView2 = null;
			ImageView imView3 = null;
			ImageView imView4 = null;
			
			if(groupPosition == 0) {
				imView1 = new ImageView(this.context);
				imView1.setImageResource(R.drawable.cupboards1);
				imView2 = new ImageView(this.context);
				imView2.setImageResource(R.drawable.cupboards2);
				imView3 = new ImageView(this.context);
				imView3.setImageResource(R.drawable.cupboards3);
				imView4 = new ImageView(this.context);
				imView4.setImageResource(R.drawable.cupboards4);
			    
				linear.addView(imView1);
				linear.addView(imView2);
				linear.addView(imView3);
				linear.addView(imView4);				
			}
			if(groupPosition == 1) {
				imView1 = new ImageView(this.context);
				imView1.setImageResource(R.drawable.camera1);
				imView2 = new ImageView(this.context);
				imView2.setImageResource(R.drawable.camera2);
				imView3 = new ImageView(this.context);
				imView3.setImageResource(R.drawable.camera3);
				imView4 = new ImageView(this.context);
				imView4.setImageResource(R.drawable.camera4);
				
				linear.addView(imView1);
				linear.addView(imView2);
				linear.addView(imView3);
				linear.addView(imView4);				
			}
			return linear;
		}
		@Override
		public int getChildrenCount(int groupPosition) {
			return 1;
		}
		@Override
		public Object getGroup(int groupPosition) {
			return null;
		}
		@Override
		public int getGroupCount() {
			return 2;
		}
		@Override
		public long getGroupId(int groupPosition) {
			return 0;
		}
		@Override
		public View getGroupView(int groupPosition, boolean isExpanded,
				View convertView, ViewGroup parent) {
			LinearLayout linear = new LinearLayout(this.context);
			ImageView imView = null;
			if(groupPosition == 0) {
				TextView txtView = new TextView(this.context);
				txtView.setText("Cup Board :");
				txtView.setTextColor(Color.BLACK);
				linear.addView(txtView);
				imView = new ImageView(this.context);
				imView.setImageResource(R.drawable.cupboards);
				linear.addView(imView);
			}
			if(groupPosition == 1) {
				TextView txtView = new TextView(this.context);
				txtView.setText("Cameras :");
				txtView.setTextColor(Color.BLACK);
				linear.addView(txtView);
				imView = new ImageView(this.context);
				imView.setImageResource(R.drawable.camerascategory);
				linear.addView(imView);
			}
			return linear;
		}
		@Override
		public boolean hasStableIds() {
			return false;
		}
		@Override
		public boolean isChildSelectable(int groupPosition, 
				                         int childPosition) {
			return true;
		}
    }
}




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