Android ใช้ asyncTask กับ Listview แล้วเกิด error ตอนดึงค่าจากฐานข้อมูลครับ

package com.example.test;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.Closeable;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.URL;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.StatusLine;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.Window;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.TextView;


public class Teacher_subject_list extends Activity  {
    
    private ListView lstView;
    private ImageAdapter imageAdapter;
    
    ArrayList<HashMap<String, Object>> MyArrList = new ArrayList<HashMap<String, Object>>();

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);        
        // ProgressBar
        requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
        
        setContentView(R.layout.teacher_subject_list);
        
        Intent intent = getIntent();
		final String Username = intent.getStringExtra("Username");

        // ListView and imageAdapter
    	lstView = (ListView) findViewById(R.id.listView1);
    	lstView.setClipToPadding(false);
        imageAdapter = new ImageAdapter(getApplicationContext()); 
        lstView.setAdapter(imageAdapter);

        setProgressBarIndeterminateVisibility(true); 
        new LoadContentFromServer().execute();
        
        final Button btn1 = (Button) findViewById(R.id.submit_stat);
        // Perform action on click
        btn1.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
            	setProgressBarIndeterminateVisibility(true);
            	new LoadContentFromServer().execute();
            }
        });
        
        final Button btnBack = (Button) findViewById(R.id.stat_back);
        // Perform action on click
        btnBack.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {        		
				Intent newActivity = new Intent(Teacher_subject_list.this,Login.class);
				newActivity.putExtra("Username", Username);
				startActivity(newActivity);
				finish();
            }
        });

    }


    class LoadContentFromServer extends AsyncTask<Object, Integer, Object> {
        
        @Override
        protected Object doInBackground(Object... params1) {
        	
        	Intent intent = getIntent();
    		final String Username = intent.getStringExtra("Username");
        	
        	final EditText inputText = (EditText)findViewById(R.id.txtid);
        	
        	String url = "http://jojomoofy.890m.com/android/getListSubject.php";
        	
        	List<NameValuePair> params = new ArrayList<NameValuePair>();
        	params.add(new BasicNameValuePair("txtKeyword", inputText.getText().toString()));
        	params.add(new BasicNameValuePair("txtUsername", Username));
        	
          	JSONArray data;
    			try {
    				data = new JSONArray(getHttpPost(url,params));
    				
    		    	MyArrList = new ArrayList<HashMap<String, Object>>();
    				HashMap<String, Object> map;
    				
    				for(int i = 0; i < data.length(); i++){
    	                JSONObject c = data.getJSONObject(i);
    	                
    	                String name = c.getString("subjectname");
    	                String check=CheckStatus(name);
    	                
    	                if(check.equals("1"))
    	                {
    	                	map = new HashMap<String, Object>();
    	                	map.put("subjectname", c.getString("subjectname"));
    	    			
    	    			// Full (for View Popup)
    	    			//map.put("ImagePathFull", (String)c.getString("ImagePath_FullPhoto"));

    	                	MyArrList.add(map);
    	                }
    	    			
    	    			publishProgress(i);
    	    				
    				}
    	    		
    				
    			} catch (JSONException e) {
    				// TODO Auto-generated catch block
    				e.printStackTrace();
    			}
 
            return null;
        }

        @Override
        public void onProgressUpdate(Integer... progress) {
        	imageAdapter.notifyDataSetChanged();
        }
        
        @Override
        protected void onPostExecute(Object result) {
            setProgressBarIndeterminateVisibility(false); // When Finish
        }
    }	
  	
	 
    class ImageAdapter extends BaseAdapter {

        private Context mContext; 

        public ImageAdapter(Context context) { 
            mContext = context; 
        } 

        public int getCount() { 
            return MyArrList.size();    
        } 

        public Object getItem(int position) { 
            return MyArrList.get(position); 
        } 

        public long getItemId(int position) { 
            return position; 
        } 

		public View getView(final int position, View convertView, ViewGroup parent) {
			// TODO Auto-generated method stub
			
			LayoutInflater inflater = (LayoutInflater) mContext
					.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
		 
			 
			if (convertView == null) {
				convertView = inflater.inflate(R.layout.column_subject_list, null); 
			}
        	
			// ColImgID
			TextView txtPicName = (TextView) convertView.findViewById(R.id.ColName2);
			txtPicName.setText(MyArrList.get(position).get("subjectname").toString());	
			
			Intent intent = getIntent();
			final String Username = intent.getStringExtra("Username");
			final int num =1;
			
			final Button bttest = (Button) convertView.findViewById(R.id.bt_test);
			// Perform action on click
			bttest.setOnClickListener(new View.OnClickListener() {
				public void onClick(View v) {
					String strsubjectname = MyArrList.get(position).get("subjectname")
							.toString();
					CreatePointAllTable(strsubjectname);
					CreateInfoTestTable(strsubjectname);
					Intent newActivity = new Intent(Teacher_subject_list.this,Teacher_question_list.class);
					newActivity.putExtra("Subjectname", strsubjectname );
					newActivity.putExtra("Username", Username );
					newActivity.putExtra("num", num);
					startActivity(newActivity);
					finish();

				}
			});
		 
			return convertView;
				
		}
        
    }
    
    public void CreatePointAllTable(String strsubjectname)
    {
    	Intent intent = getIntent();
		final String Username = intent.getStringExtra("Username");
		
		String url = "http://jojomoofy.890m.com/android/CreatePointAllTable.php";
		
		List<NameValuePair> params = new ArrayList<NameValuePair>();
        params.add(new BasicNameValuePair("sUsername", Username));
        params.add(new BasicNameValuePair("sSubjectname", strsubjectname));
        
        String resultServer  = getHttpPost(url,params);
        
        String strStatusID = "0";
    	String strError = "Unknow Status!";
    	
    	JSONObject c;
		try {
			c = new JSONObject(resultServer);
        	strStatusID = c.getString("StatusID");
        	strError = c.getString("Error");
		} catch (JSONException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
    }
    
    public void CreateInfoTestTable(String strsubjectname)
    {
    	Intent intent = getIntent();
		final String Username = intent.getStringExtra("Username");
		
		String url = "http://jojomoofy.890m.com/android/CreateInfoTestTable.php";
		
		List<NameValuePair> params = new ArrayList<NameValuePair>();
        params.add(new BasicNameValuePair("sUsername", Username));
        params.add(new BasicNameValuePair("sSubjectname", strsubjectname));
        
        String resultServer  = getHttpPost(url,params);
        
        String strStatusID = "0";
    	String strError = "Unknow Status!";
    	
    	JSONObject c;
		try {
			c = new JSONObject(resultServer);
        	strStatusID = c.getString("StatusID");
        	strError = c.getString("Error");
		} catch (JSONException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
    }
    
    public String CheckStatus(String subjectname)
    {
    	Intent intent = getIntent();
		final String Username = intent.getStringExtra("Username");
		
		String url = "http://jojomoofy.890m.com/android/CheckStatus.php";
		
		List<NameValuePair> params = new ArrayList<NameValuePair>();
        params.add(new BasicNameValuePair("sUsername", Username));
        params.add(new BasicNameValuePair("sSubjectname", subjectname));
        
        String resultServer  = getHttpPost(url,params);
        
        String Check = "0";
    	
    	JSONObject c;
		try {
			c = new JSONObject(resultServer);
        	Check = c.getString("Check");
        	
		} catch (JSONException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
        
    	return Check;
    }
    
    /*** Get JSON Code from URL ***/
    public String getHttpPost(String url,List<NameValuePair> params) {
		StringBuilder str = new StringBuilder();
		HttpClient client = new DefaultHttpClient();
		HttpPost httpPost = new HttpPost(url);
		
		try {
			httpPost.setEntity(new UrlEncodedFormEntity(params,"UTF-8"));
			HttpResponse response = client.execute(httpPost);
			StatusLine statusLine = response.getStatusLine();
			int statusCode = statusLine.getStatusCode();
			if (statusCode == 200) { // Status OK
				HttpEntity entity = response.getEntity();
				InputStream content = entity.getContent();
				BufferedReader reader = new BufferedReader(new InputStreamReader(content,"UTF-8"));
				String line;
				while ((line = reader.readLine()) != null) {
					str.append(line);
				}
			} else {
				Log.e("Log", "Failed to download result..");
			}
		} catch (ClientProtocolException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
		return str.toString();
	}

	/***** Get Image Resource from URL (End) *****/

}