Android อ่านไฟล์ Image จาก SD Card แสดงแบบ Column บน ImageView กับ GridView

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.GridView;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;
import android.app.Activity;
import android.content.Context;
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();
        
        // gridView1
        final GridView gView1 = (GridView)findViewById(R.id.gridView1); 
        	
        gView1.setAdapter(new ImageAdapter(this,ImageList));
        
        // OnClick
        gView1.setOnItemClickListener(new OnItemClickListener() {
			public void onItemClick(AdapterView<?> parent, View v,
				int position, long id) {
				
				   Toast.makeText(getApplicationContext(),
					"Your selected : " + ImageList.get(position).toString(), Toast.LENGTH_SHORT).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.showimage, null);
				}
				
				TextView textView = (TextView) convertView.findViewById(R.id.textView1);
				String strPath = lis.get(position).toString();
				
				// Get File Name
				String fileName = strPath.substring( strPath.lastIndexOf('/')+1, strPath.length() );
				textView.setText(fileName);
				
				// Image Resource
				ImageView imageView = (ImageView) convertView.findViewById(R.id.imageView1);
				Bitmap bm = BitmapFactory.decodeFile(strPath);
				imageView.setImageBitmap(bm);
		 
				return convertView;
				
		}
    } 
    
    
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }

}