Android - having trouble updating a ListAdapter after an Asynch call
===

I am setting up a ListView adapter like this:

    public class SeeAllQuestionsActivity extends Activity
    {
    	//ArrayAdapter<Question> adapter;	
    	SimpleAdapter mSchedule = null;
    	ListView list = new ListView (this);
    	
        TextView loading_questions = null;
    		
        @Override
        public void onCreate(Bundle savedInstanceState) 
        {
            super.onCreate(savedInstanceState);        
            setContentView(R.layout.all_question_page);
            
            TextView loading_questions = (TextView) findViewById(R.id.loading_questions);
            
        	list = (ListView) findViewById(R.id.list);
        	
        	ArrayList<HashMap<String, String>> mylist = new ArrayList<HashMap<String, String>>();
        	HashMap<String, String> map = new HashMap<String, String>();
        	  
        	mSchedule = new SimpleAdapter(this, mylist, R.layout.questions_list,
                    new String[] {"train", "from", "to"}, 
                    new int[] {R.id.TRAIN_CELL, R.id.FROM_CELL, R.id.TO_CELL});
        	    	
        	list.setAdapter(mSchedule);
        	
            list.setTextFilterEnabled(true);
            
            list.setOnItemClickListener(new OnItemClickListener() 
            {
                public void onItemClick(AdapterView<?> parent, View view,
                    int position, long id) 
                {              
                  ...

and then making a remote Asynch call to get the list from my database, and trying to do this in the onPostExecute method:

    ArrayList<HashMap<String, String>> mylist = new ArrayList<HashMap<String, String>>();
    		    	HashMap<String, String> map = new HashMap<String, String>();
    			    
    			        try
    			        {
    			        	JSONArray obj = new JSONArray(result);
    			        	
    			        	if ( obj != null )
    			        	{
    			        		
    			        		for ( int i = 0; i < obj.length(); i++ )
    			        		{
    			        			JSONObject o = obj.getJSONObject(i);
    
    				            	map.put("train", "Business Name");
    				            	map.put("from", ">");
    				            	map.put("to", ">");
    				            	mylist.add(map);
    				            	map = new HashMap<String, String>();
    				            	map.put("train", "103(x)");
    				            	map.put("from", "6:35 AM");
    				            	map.put("to", "7:45 AM");
    				            	mylist.add(map);						            					            
    					        }
    			        	}
    			        }
    			        catch ( Exception e )
    			        {
    			        }	        		
    
    	            	list.setAdapter(mSchedule);	        

but I get a Null Pointer exception on this line:

	ListView list = new ListView (this);

But I think generally I am way off in how this needs to be done in the postExecute method.  Any help with how to do this correctly is much appreciated.