Android ทำ Scroll ListView Endless Loading ให้เวลาเลื่อนลงมาแล้วค่อยโหลดข้อมูลเพิ่มยังไงครับ [มีภาพตัวอย่าง]

    public class EndlessScrollListener implements OnScrollListener {

        private int visibleThreshold = 5;
        private int currentPage = 0;
        private int previousTotal = 0;
        private boolean loading = true;

        public EndlessScrollListener() {
        }
        public EndlessScrollListener(int visibleThreshold) {
            this.visibleThreshold = visibleThreshold;
        }

        @Override
        public void onScroll(AbsListView view, int firstVisibleItem,
                int visibleItemCount, int totalItemCount) {
            if (loading) {
                if (totalItemCount > previousTotal) {
                    loading = false;
                    previousTotal = totalItemCount;
                    currentPage++;
                }
            }
            if (!loading && (totalItemCount - visibleItemCount) <= (firstVisibleItem + visibleThreshold)) {
                // I load the next page of gigs using a background task,
                // but you can call any function here.
                new LoadGigsTask().execute(currentPage + 1);
                loading = true;
            }
        }

        @Override
        public void onScrollStateChanged(AbsListView view, int scrollState) {
        }
    }

public class Tab_One extends Activity  {
	private ListView lstView;
	private ImageAdapter imageAdapter;
	public static final int DIALOG_DOWNLOAD_JSON_PROGRESS = 0;
    private ProgressDialog mProgressDialog;
    
    public int currentPage = 1;
    public int displayPerPage = 10;
    public int position_scroll = 0;
    public boolean loading  = false;
    public boolean stoping  = false;
    
    
    ArrayList<HashMap<String, Object>> DataList = new ArrayList<HashMap<String, Object>>();
	
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		// TODO Auto-generated method stub
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_tab1);
		
		//new  DownloadJSONAsync().execute();
		ShowData();
				
	}
	
	public void ShowData()
	{
		// ListView and imageAdapter
		lstView = (ListView) findViewById(R.id.list);
		// lstView.setClipToPadding(false);
		imageAdapter = new ImageAdapter(getApplicationContext()); 
		lstView.setAdapter(imageAdapter);
		
		
	        
		// OnClick Item
		lstView.setOnItemClickListener(new OnItemClickListener() {

			@Override
			public void onItemClick(AdapterView<?> myAdapter, View myView, int position,long mylng) {
				// TODO Auto-generated method stub
					
				// Open Intent
				Intent newActivity = new Intent(Tab_One.this,Tab_Two.class);
				newActivity.putExtra("n_id",DataList.get(position).get("n_id").toString());
				startActivity(newActivity);
					
			}
		});
		
		// ONSCROLLLISTENER
		lstView.setOnScrollListener(new OnScrollListener() {

		    @Override
		    public void onScrollStateChanged(AbsListView view, int scrollState) {

		    }

		    @Override
		    public void onScroll(AbsListView view, int firstVisibleItem,
		            int visibleItemCount, int totalItemCount) {
		    	
		       int lastInScreen = firstVisibleItem + visibleItemCount;
		      
		        if ((lastInScreen == totalItemCount) && !(loading)) {	
		        	
		        	if (stoping == false) {
		        		// FETCH THE NEXT BATCH OF FEEDS
		        		new DownloadJSONAsync().execute();
		        		loading = true;
		        		position_scroll = totalItemCount - 1;
		        		
		        	}
		        	
		        }
		    	 
		    }
		});
	}
	
	@Override
    protected Dialog onCreateDialog(int id) {
        switch (id) {
        case DIALOG_DOWNLOAD_JSON_PROGRESS:
            mProgressDialog = new ProgressDialog(this);
            mProgressDialog.setMessage("Downloading.....");
            mProgressDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
            mProgressDialog.setCancelable(true);
            mProgressDialog.show();
            return mProgressDialog;
        default:
            return null;
        }
    }
	
	
	
	
	 // Download JSON in Background
    public class DownloadJSONAsync extends AsyncTask<Object, Integer, Object> {
    	
    	
    	
        protected void onPreExecute() {
        	super.onPreExecute();
        	showDialog(DIALOG_DOWNLOAD_JSON_PROGRESS);
        }

        @Override
        protected Object doInBackground(Object... params) {
            // TODO Auto-generated method stub
        	
        	// INCREMENT CURRENT PAGE
        	//currentPage += 1;
        	
        	
    		String url = "http://10.0.2.2/project_one/android/get_news_update.php";
    		List<NameValuePair> parameter = new ArrayList<NameValuePair>();
    		parameter.add(new BasicNameValuePair("PerPage", String.valueOf(displayPerPage))); // Display Per  Page
    		parameter.add(new BasicNameValuePair("currentPage", String.valueOf(currentPage)));
    		try {
    			
    			JSONArray data = new JSONArray(getJSONUrl(url,parameter));
    			// if end last page
    			if(data.length() <=0 )
    			{
    				//currentPage = currentPage - 1;
    				
    				loading  = true;
    				
    			}
    			else
    			{
    				
    				displayPerPage += displayPerPage;
    				loading  = false;
    				
    			}
    			
    	        DataList = new ArrayList<HashMap<String, Object>>();
    			HashMap<String, Object> map;
    			
    			
    			for(int i = 0; i < data.length(); i++){
                    JSONObject c = data.getJSONObject(i);
        			map = new HashMap<String, Object>();
        			map.put("n_id", c.getString("n_id"));
        			map.put("n_title", c.getString("n_title"));
        			// Thumbnail Get ImageBitmap To Object
        			map.put("n_pic", (String)c.getString("n_pic"));
        			Bitmap newBitmap = loadBitmap(c.getString("n_pic"));
        			map.put("n_pic", newBitmap);
        			
        			DataList.add(map);
    			}
    			
    			
    			
    			
    		} catch (JSONException e) {
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		}

        	
    		return null;
        }
        
        
        @Override
        protected void onPostExecute(Object  result) {
        	ShowData();
        	// get listview current position - used to maintain scroll position
        	
            int currentPosition = lstView.getFirstVisiblePosition();
            lstView.setSelection(currentPosition + position_scroll);
            dismissDialog(DIALOG_DOWNLOAD_JSON_PROGRESS);
            removeDialog(DIALOG_DOWNLOAD_JSON_PROGRESS);
        }
        
    }
	
	
    class ImageAdapter extends BaseAdapter 
	{
		private Context context;

	 	public ImageAdapter(Context c) 
	  	{
	    	// TODO Auto-generated method stub
	 		context = c;
	  	}
	 
		public int getCount() {
	    	// TODO Auto-generated method stub
	    	return DataList.size();
	 	}
	 
		public Object getItem(int position) {
			// TODO Auto-generated method stub
			return position;
		}
		public long getItemId(int position) {
			// TODO Auto-generated method stub
			return position;
		}
		public View getView(int position, View convertView, ViewGroup parent) {
			// TODO Auto-generated method stub
			DataHolder holder = null;	
			
			if (convertView == null) {
				LayoutInflater inflater = (LayoutInflater) context
						.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
				convertView = inflater.inflate(R.layout.activity_tab1_rows, null); 
				
				holder = new DataHolder();
				holder.N_TITLE = (TextView) convertView.findViewById(R.id.title);
				holder.N_PIC = (ImageView) convertView.findViewById(R.id.list_image);
				
				convertView.setTag(holder);
			}else{
				
				holder = (DataHolder) convertView.getTag();
			}

			// Image
			holder.N_PIC.getLayoutParams().height = 100;
			holder.N_PIC.getLayoutParams().width = 100;
			holder.N_PIC.setScaleType(ImageView.ScaleType.CENTER_CROP);
			try
			{
				holder.N_PIC.setImageBitmap((Bitmap)DataList.get(position).get("n_pic"));
			} catch (Exception e) {
				// When Error
				holder.N_PIC.setImageResource(android.R.drawable.ic_menu_report_image);
				//Log.e(TAG, "Could not load pic from: " + DataList.get(position).get("n_pic"));
			}
					
			// Title
			//holder.N_TITLE.setPadding(10, 0, 0, 0);
			holder.N_TITLE.setText(DataList.get(position).get("n_title").toString());
			//holder.N_TITLE.setText("ID : " + DataArr.get(position).get("ImageID"));
			
			return convertView;
					
		}

	} 
    public class DataHolder {
    	TextView N_TITLE;
    	ImageView N_PIC;
    }
	
    /*** Get JSON Code from URL ***/
  	public String getJSONUrl(String url,List<NameValuePair> parameter) {
  		StringBuilder str = new StringBuilder();
  		HttpClient client = new DefaultHttpClient();
  		HttpPost httpPost = new HttpPost(url);
  		try {
  			httpPost.setEntity(new UrlEncodedFormEntity(parameter));
  			HttpResponse response = client.execute(httpPost);
  			StatusLine statusLine = response.getStatusLine();
  			int statusCode = statusLine.getStatusCode();
  			if (statusCode == 200) { // Download OK
  				HttpEntity entity = response.getEntity();
  				InputStream content = entity.getContent();
  				BufferedReader reader = new BufferedReader(new InputStreamReader(content));
  				String line;
  				while ((line = reader.readLine()) != null) {
  					str.append(line);
  				}
  			} else {
  				Log.e("Log", "Failed to download file..");
  			}
  		} catch (ClientProtocolException e) {
  			e.printStackTrace();
  		} catch (IOException e) {
  			e.printStackTrace();
  		}
  		return str.toString();
  	}
	
	/***** Get Image Resource from URL (Start) *****/
	private static final String TAG = "ERROR";
	private static final int IO_BUFFER_SIZE = 4 * 1024;
	public static Bitmap loadBitmap(String url) {
	    Bitmap bitmap = null;
	    InputStream in = null;
	    BufferedOutputStream out = null;

	    try {
	        in = new BufferedInputStream(new URL(url).openStream(), IO_BUFFER_SIZE);

	        final ByteArrayOutputStream dataStream = new ByteArrayOutputStream();
	        out = new BufferedOutputStream(dataStream, IO_BUFFER_SIZE);
	        copy(in, out);
	        out.flush();

	        final byte[] data = dataStream.toByteArray();
	        BitmapFactory.Options options = new BitmapFactory.Options();
	        //options.inSampleSize = 1;

	        bitmap = BitmapFactory.decodeByteArray(data, 0, data.length,options);
	    } catch (IOException e) {
	        Log.e(TAG, "Could not load Bitmap from: " + url);
	    } finally {
	        closeStream(in);
	        closeStream(out);
	    }

	    return bitmap;
	}

	 private static void closeStream(Closeable stream) {
	        if (stream != null) {
	            try {
	                stream.close();
	            } catch (IOException e) {
	                android.util.Log.e(TAG, "Could not close stream", e);
	            }
	        }
	    }
	 
	 private static void copy(InputStream in, OutputStream out) throws IOException {
        byte[] b = new byte[IO_BUFFER_SIZE];
        int read;
        while ((read = in.read(b)) != -1) {
            out.write(b, 0, read);
        }
    }
	 /***** Get Image Resource from URL (End) *****/
	 
}