Swipe to refresh listview retrieved from database after adding data android

public class Activity_update extends ActionBarActivity {

private String jsonResult;
public String url ="";
ListView listView;
List<Map<string,string>> activity = new ArrayList<Map<string,string>>();

TextView ADD,delete,edit;


@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_update);

listView = (ListView) findViewById(R.id.listView);

accessWebService();

ADD = (TextView)findViewById(R.id.add);
ADD.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
startActivity(new Intent(Activity_update.this,Training_add.class));

}
});
delete = (TextView)findViewById(R.id.delete);
delete.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
startActivity(new Intent(Activity_update.this,Training_del.class));

}
});
edit = (TextView)findViewById(R.id.edit);
edit.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
startActivity(new Intent(Activity_update.this,Training_edit.class));

}
});

}

private class JsonReadTask extends AsyncTask<string, void,="" string="">
{

@Override
protected String doInBackground(String... params)
{
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(params[0]);
try{
HttpResponse response = httpclient.execute(httppost);
jsonResult = inputStreamToString(
response.getEntity().getContent()).toString();

}catch(ClientProtocolException e){
e.printStackTrace();
} catch (IOException e){
e.printStackTrace();
}
return null;
}

private StringBuilder inputStreamToString(InputStream is){
String rLine ="";
StringBuilder answer = new StringBuilder();
BufferedReader rd = new BufferedReader(new InputStreamReader(is));
try{
while((rLine = rd.readLine()) != null){
answer.append(rLine);
}
}catch(IOException e){
Toast.makeText(getApplicationContext(),"error ..." + e.toString(), Toast.LENGTH_LONG).show();
}
return answer;
}

@Override
protected void onPostExecute(String result){
ListDrwaer(); // we will create it later
}
}

public void accessWebService(){
JsonReadTask task = new JsonReadTask();
task.execute(new String[] {url});
}

public void ListDrwaer (){
try{
JSONObject jsonResonse = new JSONObject(jsonResult.substring(jsonResult.indexOf("{"), jsonResult.lastIndexOf("}")+1));
JSONArray jsonMainNode = jsonResonse.optJSONArray("activity");

final ArrayList<hashmap<string,string>> MyArrList = new ArrayList<hashmap<string, string="">>();

HashMap<string,string> map;

for(int i=0; i<jsonmainnode.length(); i++){
="" jsonobject="" c="jsonMainNode.getJSONObject(i);

" map="new" hashmap<string,string="">();

map.put("activity", c.getString("activity"));
map.put("time", c.getString("time"));
map.put("date", c.getString("date"));

MyArrList.add(map);

SimpleAdapter sAdap;
sAdap = new SimpleAdapter(Activity_update.this, MyArrList, R.layout.activity_column, new String[]{"activity","time","date"}, new int[]{R.id.ColMemberID, R.id.ColName, R.id.Colcity});

listView.setAdapter(sAdap);





}