Android Populate ListView ImageView get Image Resource from SD Card

package com.myapp;

import java.io.File;
import java.util.ArrayList;
import java.util.List;

import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;

public class MainActivity extends Activity {
	  
    List <String> ImageList;
    
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        /*** Get Images from SDCard ***/
        ImageList = getSD();
        
        // listView1
        final ListView LView1 = (ListView)findViewById(R.id.listView1); 
        	
        LView1.setAdapter(new ImageAdapter(this,ImageList));
               
        final AlertDialog.Builder imageDialog = new AlertDialog.Builder(this);
        final LayoutInflater inflater = (LayoutInflater) this.getSystemService(LAYOUT_INFLATER_SERVICE);
        
        // OnClick
        LView1.setOnItemClickListener(new OnItemClickListener() {
			public void onItemClick(AdapterView<?> parent, View v,
				int position, long id) {
				
                View layout = inflater.inflate(R.layout.custom_fullimage_dialog,
                        (ViewGroup) findViewById(R.id.layout_root));
                ImageView image = (ImageView) layout.findViewById(R.id.fullimage);
                
                String strPath = ImageList.get(position).toString();
				Bitmap bm = BitmapFactory.decodeFile(strPath);
				int width=200;
			    int height=200;
			    Bitmap resizedbitmap = Bitmap.createScaledBitmap(bm, width, height, true);
				image.setImageBitmap(resizedbitmap);
				
                imageDialog.setIcon(android.R.drawable.btn_star_big_on);	
                String fileName = strPath.substring( strPath.lastIndexOf('/')+1, strPath.length());
        		imageDialog.setTitle("View : " + fileName);
                imageDialog.setView(layout);
                imageDialog.setPositiveButton(android.R.string.ok, new DialogInterface.OnClickListener(){

                    public void onClick(DialogInterface dialog, int which) {
                        dialog.dismiss();
                    }

                });


                imageDialog.create();
                imageDialog.show(); 
		    	
			}
		});
    
      
    }

    private List <String> getSD()
    {
	    List <String> it = new ArrayList <String>();
	    File f = new File ("/mnt/sdcard/picture");
	    File[] files = f.listFiles ();
	    
	    for (int i = 0; i <files.length; i++)
	    {
	    	File  file = files[i];
	    	Log.d("Count",file.getPath());
		    it.add (file.getPath());
	    }
	    return it;
    }
    
    public class ImageAdapter extends BaseAdapter 
    {
        private Context context;
        private List <String> lis;
        
        public ImageAdapter(Context c, List <String> li) 
        {
        	// TODO Auto-generated method stub
            context = c;
            lis = li;
        }
 
        public int getCount() {
        	// TODO Auto-generated method stub
            return lis.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
			
			LayoutInflater inflater = (LayoutInflater) context
					.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
		 
			if (convertView == null) {
				convertView = inflater.inflate(R.layout.activity_column, null); 
			}
					
			// ColImage
			String strPath = lis.get(position).toString();
			Bitmap bm = BitmapFactory.decodeFile(strPath);

			ImageView imageView = (ImageView) convertView.findViewById(R.id.ColImage);
			imageView.getLayoutParams().height = 100;
			imageView.getLayoutParams().width = 100;
			imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
			imageView.setImageBitmap(bm);
			
			// ColPosition
			TextView txtPosition = (TextView) convertView.findViewById(R.id.ColPosition);
			txtPosition.setPadding(10, 0, 0, 0);
			txtPosition.setText("Position : " + position);
			
			// ColPicname
			TextView txtPicName = (TextView) convertView.findViewById(R.id.ColPicname);
			txtPicName.setPadding(50, 0, 0, 0);
			String fileName = strPath.substring( strPath.lastIndexOf('/')+1, strPath.length());
			txtPicName.setText("Pic : " + fileName);

		 
			return convertView;
				
		}

    } 
    
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }

}