Fail to display server's respond
===

Here I am trying to retrieve the response from the server and display it, but I am failed to do so, the response text does not appear in my text view, insetead the default value of the string does, may I ask how can I achieve my goal. And why my code cannot finish the task.

Here is my android program:

    public class Chico extends Activity {

	GrabURL grab;
	TextView mRespond;
	String line;
	
    @Override
    public void onCreate(Bundle savedInstanceState) {
        
    	//create the activity
    	super.onCreate(savedInstanceState);
        
    	//set up the layout
    	setContentView(R.layout.activity_chico);

    	mRespond = (TextView) findViewById(R.id.Respond);
    	mRespond.setVisibility(View.GONE);
    	
    	grab = new GrabURL();
          line = "line";
    	
    	//set up the button for check in
        Button btnin = (Button) findViewById(R.id.inbutton);
        btnin.setOnClickListener(new View.OnClickListener() {
			@Override
			public void onClick(View v) {
				// TODO Auto-generated method stub
				//set the values
				grab.onPreExecute("TechID", Build.SERIAL);
	    		grab.onPreExecute("Type", "Checkin");
	    		//set the destination and send the request
				grab.execute(new String[]{"http://192.168.1.150/Me/testing.php"});
				//close the activity
				mRespond.setVisibility(View.VISIBLE);
				mRespond.setText(line);
				//finish();
			}
		}); 
    }
   
    private class GrabURL extends AsyncTask<String, Void, Void>{
    	//ArrayList object for storing the string pairs
    	ArrayList<NameValuePair> nameValuePairs;
    	 
    	public GrabURL() { 
    		//constructor of the class
    	    nameValuePairs = new ArrayList<NameValuePair>(); 
    	  } 

    	
    	protected void onPreExecute(String key, String value) {
    		//store the pair of values into the ArrayList 
    		nameValuePairs.add(new BasicNameValuePair(key,value));
    		}
    	
		@Override
		protected Void doInBackground(String... urls) {
			// TODO Auto-generated method stub
			//Operation being executed in another thread
			try{
				//set up the type of HTTPClient
				HttpClient client = new DefaultHttpClient();
				//set up the location of the server
		        HttpPost post = new HttpPost(urls[0]);
		        //translate form of pairs to UrlEncodedFormEntity 
		        UrlEncodedFormEntity ent = new UrlEncodedFormEntity(nameValuePairs,HTTP.UTF_8);
	            //set up the entity being sent by post method
		        post.setEntity(ent);
		        //execute the url and post the values
	            HttpResponse responsePOST = client.execute(post); 
	            HttpEntity resEntity = responsePOST.getEntity();
	            line = EntityUtils.toString(resEntity);
			 } catch (Exception e) {
				 //catch the exception
			    line = "Can't connect to server";
			 }
			return null;
		}
		
		protected void onPostExecute(Void unused) {
			Toast.makeText(getApplicationContext(), "Value updated", Toast.LENGTH_SHORT).show();
		}
        }
    
    }

And here is the php file, it just prints a line:

    <?php
	print "testing";	
    ?>